blob: d05533e6120ba8c8ea01e769cdc30aa4125dcbe6 [file] [log] [blame]
Al Stoneb10d79f2015-03-24 14:02:41 +00001 acpi= [HW,ACPI,X86,ARM64]
Bernhard Walle03d926f2007-03-06 02:29:44 -08002 Advanced Configuration and Power Interface
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +02003 Format: { force | on | off | strict | noirq | rsdt |
Rami Rosene58d1542015-09-26 19:27:57 +03004 copy_dsdt }
Linus Torvalds1da177e2005-04-16 15:20:36 -07005 force -- enable ACPI if default was off
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +02006 on -- enable ACPI but allow fallback to DT [arm64]
Linus Torvalds1da177e2005-04-16 15:20:36 -07007 off -- disable ACPI if default was on
8 noirq -- do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07009 strict -- Be less tolerant of platforms that are not
Linus Torvalds1da177e2005-04-16 15:20:36 -070010 strictly ACPI specification compliant.
Zhao Yakui237889b2008-12-17 16:55:18 +080011 rsdt -- prefer RSDT over (default) XSDT
Lin Mingaa2110c2010-04-08 14:34:27 +080012 copy_dsdt -- copy DSDT to memory
Ard Biesheuvel6a1f5472016-04-12 16:09:11 +020013 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
14 are available
Linus Torvalds1da177e2005-04-16 15:20:36 -070015
Paul Bolle395cf962011-08-15 02:02:26 +020016 See also Documentation/power/runtime_pm.txt, pci=noacpi
Linus Torvalds1da177e2005-04-16 15:20:36 -070017
Len Browna1fdcc02007-03-11 03:26:14 -040018 acpi_apic_instance= [ACPI, IOAPIC]
19 Format: <int>
20 2: use 2nd APIC table, if available
21 1,0: use 1st APIC table
Len Brown4e381a42007-03-30 14:16:10 -040022 default: 0
Len Browna1fdcc02007-03-11 03:26:14 -040023
Thomas Renningerc3d6de62008-08-01 17:37:55 +020024 acpi_backlight= [HW,ACPI]
25 acpi_backlight=vendor
26 acpi_backlight=video
27 If set to vendor, prefer vendor specific driver
28 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
29 of the ACPI video.ko driver.
30
Colin Ian Kingb2ca5da2016-01-21 17:05:47 +000031 acpi_force_32bit_fadt_addr
32 force FADT to use 32 bit addresses rather than the
33 64 bit X_* addresses. Some firmware have broken 64
34 bit addresses for force ACPI ignore these and use
35 the older legacy 32 bit addresses.
36
Dominik Brodowskief694492015-05-14 15:31:28 +020037 acpica_no_return_repair [HW, ACPI]
38 Disable AML predefined validation mechanism
39 This mechanism can repair the evaluation result to make
40 the return objects more ACPI specification compliant.
41 This option is useful for developers to identify the
42 root cause of an AML interpreter issue when the issue
43 has something to do with the repair mechanism.
44
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070045 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
46 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
Linus Torvalds1da177e2005-04-16 15:20:36 -070047 Format: <int>
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070048 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
49 debug output. Bits in debug_layer correspond to a
50 _COMPONENT in an ACPI source file, e.g.,
51 #define _COMPONENT ACPI_PCI_COMPONENT
52 Bits in debug_level correspond to a level in
53 ACPI_DEBUG_PRINT statements, e.g.,
54 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
Bjorn Helgaase76f4272008-11-13 17:30:13 -060055 The debug_level mask defaults to "info". See
56 Documentation/acpi/debug.txt for more information about
57 debug layers and levels.
Linus Torvalds1da177e2005-04-16 15:20:36 -070058
Bjorn Helgaase76f4272008-11-13 17:30:13 -060059 Enable processor driver info messages:
60 acpi.debug_layer=0x20000000
61 Enable PCI/PCI interrupt routing info messages:
62 acpi.debug_layer=0x400000
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070063 Enable AML "Debug" output, i.e., stores to the Debug
64 object while interpreting AML:
65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070066 Enable all messages related to ACPI hardware:
67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
Thomas Renninger36eec5e2008-08-11 15:03:20 +020068
Bjorn Helgaasa0d84a92008-11-07 16:58:05 -070069 Some values produce so much output that the system is
70 unusable. The "log_buf_len" parameter may be useful
71 if you need to capture more output.
Zhang Ruif9891062007-04-24 13:53:22 +080072
Dominik Brodowskief694492015-05-14 15:31:28 +020073 acpi_enforce_resources= [ACPI]
74 { strict | lax | no }
75 Check for resource conflicts between native drivers
76 and ACPI OperationRegions (SystemIO and SystemMemory
77 only). IO ports and memory declared in ACPI might be
78 used by the ACPI subsystem in arbitrary AML code and
79 can interfere with legacy drivers.
80 strict (default): access to resources claimed by ACPI
81 is denied; legacy drivers trying to access reserved
82 resources will fail to bind to device using them.
83 lax: access to resources claimed by ACPI is allowed;
84 legacy drivers trying to access reserved resources
85 will bind successfully but a warning message is logged.
86 no: ACPI OperationRegions are not marked as reserved,
87 no further checks are performed.
88
Lv Zheng4fc0a7e2014-05-31 08:15:02 +080089 acpi_force_table_verification [HW,ACPI]
90 Enable table checksum verification during early stage.
91 By default, this is disabled due to x86 early mapping
92 size limitation.
93
Randy Dunlap0cb55ad2009-04-05 15:55:22 -070094 acpi_irq_balance [HW,ACPI]
95 ACPI will balance active IRQs
96 default in APIC mode
97
98 acpi_irq_nobalance [HW,ACPI]
99 ACPI will not move active IRQs (default)
100 default in PIC mode
101
102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
103 Format: <irq>,<irq>...
104
105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
106 use by PCI
107 Format: <irq>,<irq>...
108
Lv Zheng9c4aa1e2016-12-16 12:07:57 +0800109 acpi_mask_gpe= [HW,ACPI]
110 Due to the existence of _Lxx/_Exx, some GPEs triggered
111 by unsupported hardware/firmware features can result in
112 GPE floodings that cannot be automatically disabled by
113 the GPE dispatcher.
114 This facility can be used to prevent such uncontrolled
115 GPE floodings.
116 Format: <int>
117 Support masking of GPEs numbered from 0x00 to 0x7f.
118
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800119 acpi_no_auto_serialize [HW,ACPI]
120 Disable auto-serialization of AML methods
Bob Moore22b5afc2014-03-24 14:49:00 +0800121 AML control methods that contain the opcodes to create
122 named objects will be marked as "Serialized" by the
123 auto-serialization feature.
Lv Zheng08e1d7c2014-03-24 14:49:22 +0800124 This feature is enabled by default.
125 This option allows to turn off the feature.
Bob Moore22b5afc2014-03-24 14:49:00 +0800126
Dominik Brodowskief694492015-05-14 15:31:28 +0200127 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
128 kernels.
129
Lv Zhenga94e88c2014-04-04 12:39:11 +0800130 acpi_no_static_ssdt [HW,ACPI]
131 Disable installation of static SSDTs at early boot time
132 By default, SSDTs contained in the RSDT/XSDT will be
133 installed automatically and they will appear under
134 /sys/firmware/acpi/tables.
135 This option turns off this feature.
136 Note that specifying this option does not affect
137 dynamic table installation which will install SSDT
138 tables to /sys/firmware/acpi/tables/dynamic.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700139
Dominik Brodowskief694492015-05-14 15:31:28 +0200140 acpi_rsdp= [ACPI,EFI,KEXEC]
141 Pass the RSDP address to the kernel, mostly used
142 on machines running EFI runtime service to boot the
143 second kernel for kdump.
Lv Zheng4dde5072014-02-11 11:01:52 +0800144
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700145 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
146 Format: To spoof as Windows 98: ="Microsoft Windows"
147
Rafael J. Wysocki18d78b62015-07-03 01:06:00 +0200148 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
149 of 2 which is mandated by ACPI 6) as the supported ACPI
150 specification revision (when using this switch, it may
151 be necessary to carry out a cold reboot _twice_ in a
152 row to make it take effect on the platform firmware).
153
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700154 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800155 acpi_osi="string1" # add string1
156 acpi_osi="!string2" # remove string2
Lv Zheng741d8122013-07-22 16:08:36 +0800157 acpi_osi=!* # remove all strings
Lv Zheng5dc17982013-07-22 16:08:25 +0800158 acpi_osi=! # disable all built-in OS vendor
159 strings
Lv Zhenga707ede2016-05-03 16:48:32 +0800160 acpi_osi=!! # enable all built-in OS vendor
161 strings
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700162 acpi_osi= # disable all strings
163
Lv Zheng5dc17982013-07-22 16:08:25 +0800164 'acpi_osi=!' can be used in combination with single or
165 multiple 'acpi_osi="string1"' to support specific OS
166 vendor string(s). Note that such command can only
167 affect the default state of the OS vendor strings, thus
168 it cannot affect the default state of the feature group
169 strings and the current state of the OS vendor strings,
170 specifying it multiple times through kernel command line
Lv Zheng741d8122013-07-22 16:08:36 +0800171 is meaningless. This command is useful when one do not
172 care about the state of the feature group strings which
173 should be controlled by the OSPM.
Lv Zheng5dc17982013-07-22 16:08:25 +0800174 Examples:
175 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
176 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
177 can make '_OSI("Windows 2000")' TRUE.
178
179 'acpi_osi=' cannot be used in combination with other
180 'acpi_osi=' command lines, the _OSI method will not
181 exist in the ACPI namespace. NOTE that such command can
182 only affect the _OSI support state, thus specifying it
183 multiple times through kernel command line is also
184 meaningless.
185 Examples:
186 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
187 FALSE.
188
Lv Zheng741d8122013-07-22 16:08:36 +0800189 'acpi_osi=!*' can be used in combination with single or
190 multiple 'acpi_osi="string1"' to support specific
191 string(s). Note that such command can affect the
192 current state of both the OS vendor strings and the
193 feature group strings, thus specifying it multiple times
194 through kernel command line is meaningful. But it may
195 still not able to affect the final state of a string if
196 there are quirks related to this string. This command
197 is useful when one want to control the state of the
198 feature group strings to debug BIOS issues related to
199 the OSPM features.
200 Examples:
201 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
202 '_OSI("Module Device")' FALSE.
203 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
204 '_OSI("Module Device")' TRUE.
205 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
206 equivalent to
207 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
208 and
209 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
210 they all will make '_OSI("Windows 2000")' TRUE.
211
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530212 acpi_pm_good [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700213 Override the pmtimer bug detection: force the kernel
214 to assume that this machine's pmtimer latches its value
215 and always returns good values.
216
Randy Dunlap4af94f32009-04-17 18:30:28 -0700217 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
218 Format: { level | edge | high | low }
219
Randy Dunlap4af94f32009-04-17 18:30:28 -0700220 acpi_skip_timer_override [HW,ACPI]
221 Recognize and ignore IRQ0/pin2 Interrupt Override.
222 For broken nForce2 BIOS resulting in XT-PIC timer.
223
224 acpi_sleep= [HW,ACPI] Sleep options
225 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
Amerigo Wangc3b07952011-05-10 21:09:38 +0200226 old_ordering, nonvs, sci_force_enable }
Randy Dunlap4af94f32009-04-17 18:30:28 -0700227 See Documentation/power/video.txt for information on
228 s3_bios and s3_mode.
229 s3_beep is for debugging; it makes the PC's speaker beep
230 as soon as the kernel's real-mode entry point is called.
231 s4_nohwsig prevents ACPI hardware signature from being
232 used during resume from hibernation.
233 old_ordering causes the ACPI 1.0 ordering of the _PTS
234 control method, with respect to putting devices into
235 low power states, to be enforced (the ACPI 2.0 ordering
236 of _PTS is used by default).
Rafael J. Wysocki72ad5d72010-07-23 22:59:09 +0200237 nonvs prevents the kernel from saving/restoring the
238 ACPI NVS memory during suspend/hibernation and resume.
Zhang Ruid7f0eea2009-12-30 15:36:42 +0800239 sci_force_enable causes the kernel to set SCI_EN directly
240 on resume from S1/S3 (which is against the ACPI spec,
241 but some broken systems don't work without it).
Randy Dunlap4af94f32009-04-17 18:30:28 -0700242
243 acpi_use_timer_override [HW,ACPI]
244 Use timer override. For some broken Nvidia NF5 boards
245 that require a timer override, but don't have HPET
246
Randy Dunlap4af94f32009-04-17 18:30:28 -0700247 add_efi_memmap [EFI; X86] Include EFI memory map in
248 kernel's map of available physical RAM.
249
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700250 agp= [AGP]
251 { off | try_unsupported }
252 off: disable AGP support
253 try_unsupported: try to drive unsupported chipsets
254 (may crash computer or cause data corruption)
255
Randy Dunlapbcfde332010-06-07 17:10:38 -0700256 ALSA [HW,ALSA]
257 See Documentation/sound/alsa/alsa-parameters.txt
258
Russell Kingd944d542010-02-20 16:13:29 +0000259 alignment= [KNL,ARM]
260 Allow the default userspace alignment fault handler
261 behaviour to be specified. Bit 0 enables warnings,
262 bit 1 enables fixups, and bit 2 sends a segfault.
263
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200264 align_va_addr= [X86-64]
265 Align virtual addresses by clearing slice [14:12] when
266 allocating a VMA at process creation time. This option
267 gives you up to 3% performance improvement on AMD F15h
268 machines (where it is enabled by default) for a
269 CPU-intensive style benchmark, and it can vary highly in
270 a microbenchmark depending on workload and compiler.
271
Borislav Petkov8360ee22011-11-21 12:10:19 +0100272 32: only for 32-bit processes
273 64: only for 64-bit processes
Borislav Petkovdfb09f92011-08-05 15:15:08 +0200274 on: enable for both 32- and 64-bit processes
275 off: disable for both 32- and 64-bit processes
276
Steven Rostedt (Red Hat)55034cd2013-03-07 22:48:09 -0500277 alloc_snapshot [FTRACE]
278 Allocate the ftrace snapshot buffer on boot up when the
279 main buffer is allocated. This is handy if debugging
280 and you need to use tracing_snapshot() on boot up, and
281 do not want to use tracing_snapshot_alloc() as it needs
282 to be done where GFP_KERNEL allocations are allowed.
283
Sedat Dilek89e0b9a2011-12-05 23:08:32 +0100284 amd_iommu= [HW,X86-64]
Joerg Roedel54b4cbd2008-06-26 21:28:10 +0200285 Pass parameters to the AMD IOMMU driver in the system.
286 Possible values are:
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900287 fullflush - enable flushing of IO/TLB entries when
288 they are unmapped. Otherwise they are
289 flushed before they will be reused, which
290 is a lot of faster
Joerg Roedela5235722010-05-11 17:12:33 +0200291 off - do not initialize any AMD IOMMU found in
292 the system
Joerg Roedel5abcdba2011-12-01 15:49:45 +0100293 force_isolation - Force device isolation for all
294 devices. The IOMMU driver is not
295 allowed anymore to lift isolation
296 requirements as needed. This option
297 does not override iommu=pt
FUJITA Tomonoriafa9fdc2008-09-20 01:23:30 +0900298
Shuah Khanc099cf12012-05-24 15:58:25 -0600299 amd_iommu_dump= [HW,X86-64]
300 Enable AMD IOMMU driver option to dump the ACPI table
301 for AMD IOMMU. With this option enabled, AMD IOMMU
302 driver will print ACPI tables for AMD IOMMU during
303 IOMMU initialization.
304
Suravee Suthikulpanit3928aa32016-08-23 13:52:32 -0500305 amd_iommu_intr= [HW,X86-64]
306 Specifies one of the following AMD IOMMU interrupt
307 remapping modes:
308 legacy - Use legacy interrupt remapping mode.
309 vapic - Use virtual APIC mode, which allows IOMMU
310 to inject interrupts directly into guest.
311 This mode requires kvm-amd.avic=1.
312 (Default when IOMMU HW support is present.)
313
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314 amijoy.map= [HW,JOY] Amiga joystick support
315 Map of devices attached to JOY0DAT and JOY1DAT
316 Format: <a>,<b>
Paul Bolle395cf962011-08-15 02:02:26 +0200317 See also Documentation/input/joystick.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -0700318
319 analog.map= [HW,JOY] Analog joystick and gamepad support
320 Specifies type or capabilities of an analog joystick
321 connected to one of 16 gameports
322 Format: <type1>,<type2>,..<type16>
323
Randy Dunlapa9913042005-10-23 12:57:11 -0700324 apc= [HW,SPARC]
325 Power management functions (SPARCstation-4/5 + deriv.)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700326 Format: noidle
327 Disable APC CPU standby support. SPARCstation-Fox does
328 not play well with APC CPU idle - disable it if you have
329 APC and your system crashes randomly.
330
Randy Dunlapca1eda22009-05-06 16:02:58 -0700331 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
Randy Dunlapc8facbb2007-07-31 00:37:40 -0700332 Change the output verbosity whilst booting
Linus Torvalds1da177e2005-04-16 15:20:36 -0700333 Format: { quiet (default) | verbose | debug }
334 Change the amount of debugging information output
335 when initialising the APIC and IO-APIC components.
Randy Dunlapa9913042005-10-23 12:57:11 -0700336
Hidehiro Kawaib7c49482015-12-14 11:19:12 +0100337 apic_extnmi= [APIC,X86] External NMI delivery setting
338 Format: { bsp (default) | all | none }
339 bsp: External NMI is delivered only to CPU 0
340 all: External NMIs are broadcast to all CPUs as a
341 backup of CPU 0
342 none: External NMI is masked for all CPUs. This is
343 useful so that a dump capture kernel won't be
344 shot down by NMI
345
Brian Haleyb0f83b22010-02-04 13:36:50 -0800346 autoconf= [IPV6]
347 See Documentation/networking/ipv6.txt.
348
Cyrill Gorcunov9636bc02009-10-14 19:09:04 +0400349 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
350 Limit apic dumping. The parameter defines the maximal
351 number of local apics being dumped. Also it is possible
352 to set it to "all" by meaning -- no limit here.
353 Format: { 1 (default) | 2 | ... | all }.
354 The parameter valid if only apic=debug or
355 apic=verbose is specified.
356 Example: apic=debug show_lapic=all
357
Linus Torvalds1da177e2005-04-16 15:20:36 -0700358 apm= [APM] Advanced Power Management
Pavel Machek71f77052008-07-04 09:59:43 -0700359 See header of arch/x86/kernel/apm_32.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700360
Linus Torvalds1da177e2005-04-16 15:20:36 -0700361 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
362 Format: <io>,<irq>,<nodeID>
363
364 ataflop= [HW,M68k]
365
366 atarimouse= [HW,MOUSE] Atari Mouse
367
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
369 EzKey and similar keyboards
370
371 atkbd.reset= [HW] Reset keyboard during initialization
372
Randy Dunlapa9913042005-10-23 12:57:11 -0700373 atkbd.set= [HW] Select keyboard code set
374 Format: <int> (2 = AT (default), 3 = PS/2)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375
376 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
377 keyboards
378
379 atkbd.softraw= [HW] Choose between synthetic and real raw mode
380 Format: <bool> (0 = real, 1 = synthetic (default))
Randy Dunlapa9913042005-10-23 12:57:11 -0700381
382 atkbd.softrepeat= [HW]
383 Use software keyboard repeat
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400385 audit= [KNL] Enable the audit sub-system
386 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
Eric Parisd7961142014-01-13 16:01:06 -0500387 0 - kernel audit is disabled and can not be enabled
388 until the next reboot
389 unset - kernel audit is initialized but disabled and
390 will be fully enabled by the userspace auditd.
391 1 - kernel audit is initialized and partially enabled,
392 storing at most audit_backlog_limit messages in
393 RAM until it is fully enabled by the userspace
394 auditd.
Richard Guy Briggsa106fb02013-09-23 21:53:35 -0400395 Default: unset
Richard Guy Briggsf3411cb2013-09-17 12:34:52 -0400396
Richard Guy Briggsf910fde2013-09-17 12:34:52 -0400397 audit_backlog_limit= [KNL] Set the audit queue size limit.
398 Format: <int> (must be >=0)
399 Default: 64
400
Alex Thorlton1c532e02016-03-31 14:18:29 -0500401 bau= [X86_UV] Enable the BAU on SGI UV. The default
402 behavior is to disable the BAU (i.e. bau=0).
403 Format: { "0" | "1" }
404 0 - Disable the BAU.
405 1 - Enable the BAU.
406 unset - Disable the BAU.
407
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408 baycom_epp= [HW,AX25]
409 Format: <io>,<mode>
Randy Dunlapa9913042005-10-23 12:57:11 -0700410
Linus Torvalds1da177e2005-04-16 15:20:36 -0700411 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
412 Format: <io>,<mode>
413 See header of drivers/net/hamradio/baycom_par.c.
414
Randy Dunlapa9913042005-10-23 12:57:11 -0700415 baycom_ser_fdx= [HW,AX25]
416 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700417 Format: <io>,<irq>,<mode>[,<baud>]
418 See header of drivers/net/hamradio/baycom_ser_fdx.c.
419
Randy Dunlapa9913042005-10-23 12:57:11 -0700420 baycom_ser_hdx= [HW,AX25]
421 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422 Format: <io>,<irq>,<mode>
423 See header of drivers/net/hamradio/baycom_ser_hdx.c.
424
Paul Gortmaker080506a2013-09-30 13:45:19 -0700425 blkdevparts= Manual partition parsing of block device(s) for
426 embedded devices based on command line input.
427 See Documentation/block/cmdline-partition.txt
428
Randy Dunlapbfe8df32007-10-16 01:23:46 -0700429 boot_delay= Milliseconds to delay each printk during boot.
430 Values larger than 10 seconds (10000) are changed to
431 no delay (0).
432 Format: integer
433
Andreas Herrmann35fc9082008-08-20 14:08:58 -0700434 bootmem_debug [KNL] Enable bootmem allocator debug messages.
435
Huang Yinga3e2acc2016-06-29 13:04:29 -0700436 bert_disable [ACPI]
437 Disable BERT OS support on buggy BIOSes.
438
Linus Torvalds1da177e2005-04-16 15:20:36 -0700439 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
Randy Dunlapa9913042005-10-23 12:57:11 -0700440 bttv.radio= Most important insmod options are available as
441 kernel args too.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
Paul Bolle395cf962011-08-15 02:02:26 +0200443 bttv.tuner=
Linus Torvalds1da177e2005-04-16 15:20:36 -0700444
Will Schmidt4e89a2d2010-09-28 15:33:12 +0000445 bulk_remove=off [PPC] This parameter disables the use of the pSeries
446 firmware feature for flushing multiple hpte entries
447 at a time.
448
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449 c101= [NET] Moxa C101 synchronous serial card
450
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700451 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452 Sometimes CPU hardware bugs make them report the cache
453 size incorrectly. The kernel will attempt work arounds
454 to fix known problems, but for some CPUs it is not
455 possible to determine what the correct size should be.
456 This option provides an override for these situations.
457
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300458 ca_keys= [KEYS] This parameter identifies a specific key(s) on
459 the system trusted keyring to be used for certificate
460 trust validation.
Dmitry Kasatkin32c47412014-06-17 11:56:59 +0300461 format: { id:<keyid> | builtin }
Dmitry Kasatkinffb70f62014-06-17 11:56:58 +0300462
Florian Fainellifd1bb4c2014-06-25 16:41:13 -0700463 cca= [MIPS] Override the kernel pages' cache coherency
464 algorithm. Accepted values range from 0 to 7
465 inclusive. See arch/mips/include/asm/pgtable-bits.h
466 for platform specific values (SB1, Loongson3 and
467 others).
468
Sebastian Ott14ff56b2008-01-26 14:10:37 +0100469 ccw_timeout_log [S390]
470 See Documentation/s390/CommonIO for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700471
Paul Menage8bab8dd2008-04-04 14:29:57 -0700472 cgroup_disable= [KNL] Disable a particular controller
473 Format: {name of the controller(s) to disable}
Qiang Huangca0bdbb2013-11-06 13:18:09 -0800474 The effects of cgroup_disable=foo are:
475 - foo isn't auto-mounted if you mount all cgroups in
476 a single hierarchy
477 - foo isn't visible as an individually mountable
478 subsystem
479 {Currently only "memory" controller deal with this and
480 cut the overhead, others just disable the usage. So
481 only cgroup_disable=memory is actually worthy}
Paul Menage8bab8dd2008-04-04 14:29:57 -0700482
Johannes Weiner1619b6d2016-02-16 13:21:14 -0500483 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
484 Format: { controller[,controller...] | "all" }
485 Like cgroup_disable, but only applies to cgroup v1;
486 the blacklisted controllers remain available in cgroup2.
487
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800488 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
489 Format: <string>
490 nosocket -- Disable socket memory accounting.
Vladimir Davydov04823c82016-01-20 15:02:38 -0800491 nokmem -- Disable kernel memory accounting.
Johannes Weinerf7e1cb62016-01-14 15:21:29 -0800492
Linus Torvalds1da177e2005-04-16 15:20:36 -0700493 checkreqprot [SELINUX] Set initial checkreqprot flag value.
494 Format: { "0" | "1" }
495 See security/selinux/Kconfig help text.
Randy Dunlapa9913042005-10-23 12:57:11 -0700496 0 -- check protection applied by kernel (includes
497 any implied execute protection).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700498 1 -- check protection requested by application.
499 Default value is set via a kernel config option.
Randy Dunlapa9913042005-10-23 12:57:11 -0700500 Value can be changed at runtime via
501 /selinux/checkreqprot.
502
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100503 cio_ignore= [S390]
504 See Documentation/s390/CommonIO for details.
Olof Johansson1e435252013-04-27 14:10:18 -0700505 clk_ignore_unused
506 [CLK]
Mike Turquettee156ee52014-09-30 14:24:38 -0700507 Prevents the clock framework from automatically gating
508 clocks that have not been explicitly enabled by a Linux
509 device driver but are enabled in hardware at reset or
510 by the bootloader/firmware. Note that this does not
511 force such clocks to be always-on nor does it reserve
512 those clocks in any way. This parameter is useful for
513 debug and development, but should not be needed on a
514 platform with proper driver support. For more
515 information, see Documentation/clk.txt.
Sebastian Ott661ca0d2008-01-26 14:10:36 +0100516
Alan Coxcd4f0ef2007-07-31 00:37:59 -0700517 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
john stultz734efb42006-06-26 00:25:05 -0700518 [Deprecated]
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200519 Forces specified clocksource (if available) to be used
john stultz734efb42006-06-26 00:25:05 -0700520 when calculating gettimeofday(). If specified
Matt LaPlante3f6dee92006-10-03 22:45:33 +0200521 clocksource is not available, it defaults to PIT.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 Format: { pit | tsc | cyclone | pmtmr }
523
John Stultz592913e2010-07-13 17:56:20 -0700524 clocksource= Override the default clocksource
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700525 Format: <string>
526 Override the default clocksource and use the clocksource
527 with the name specified.
528 Some clocksource names to choose from, depending on
529 the platform:
530 [all] jiffies (this is the base, fallback clocksource)
531 [ACPI] acpi_pm
532 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
533 pxa_timer,timer3,32k_counter,timer0_1
534 [AVR32] avr32
Alok Kataria9863c902010-08-23 14:49:11 -0700535 [X86-32] pit,hpet,tsc;
Randy Dunlap3d6ac982007-05-23 13:58:16 -0700536 scx200_hrt on Geode; cyclone on IBM x440
537 [MIPS] MIPS
538 [PARISC] cr16
539 [S390] tod
540 [SH] SuperH
541 [SPARC64] tick
542 [X86-64] hpet,tsc
543
Will Deacon46fd5c62016-06-27 17:30:13 +0100544 clocksource.arm_arch_timer.evtstrm=
545 [ARM,ARM64]
546 Format: <bool>
547 Enable/disable the eventstream feature of the ARM
548 architected timer so that code using WFE-based polling
549 loops can be debugged more effectively on production
550 systems.
551
Andi Kleenac72e782008-01-30 13:33:21 +0100552 clearcpuid=BITNUM [X86]
553 Disable CPUID feature X for the kernel. See
Borislav Petkovcd4d09e2016-01-26 22:12:04 +0100554 arch/x86/include/asm/cpufeatures.h for the valid bit
Randy Dunlap07983f02009-01-06 14:42:41 -0800555 numbers. Note the Linux specific bits are not necessarily
Andi Kleenac72e782008-01-30 13:33:21 +0100556 stable over kernel options, but the vendor specific
557 ones should be.
558 Also note that user programs calling CPUID directly
559 or using the feature without checking anything
560 will still see it. This just prevents it from
561 being used by the kernel or shown in /proc/cpuinfo.
562 Also note the kernel might malfunction if you disable
563 some critical bits.
564
Akinobu Mita5ea3b1b2014-06-04 16:06:54 -0700565 cma=nn[MG]@[start[MG][-end[MG]]]
566 [ARM,X86,KNL]
567 Sets the size of kernel global memory area for
568 contiguous memory allocations and optionally the
569 placement constraint by the physical address range of
Jean Delvaref0d6d1f2014-10-09 15:29:41 -0700570 memory allocations. A value of 0 disables CMA
571 altogether. For more information, see
Marek Szyprowskic64be2b2011-12-29 13:09:51 +0100572 include/linux/dma-contiguous.h
573
Robert Jennings14f966e2009-04-15 05:55:32 +0000574 cmo_free_hint= [PPC] Format: { yes | no }
575 Specify whether pages are marked as being inactive
576 when they are freed. This is used in CMO environments
577 to determine OS memory pressure for page stealing by
578 a hypervisor.
579 Default: yes
580
Marek Szyprowskic7909502011-12-29 13:09:51 +0100581 coherent_pool=nn[KMG] [ARM,KNL]
582 Sets the size of memory pool for coherent, atomic dma
Marek Szyprowskie9da6e92012-07-30 09:11:33 +0200583 allocations, by default set to 256K.
Marek Szyprowskic7909502011-12-29 13:09:51 +0100584
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530585 code_bytes [X86] How many bytes of object code to print
Arjan van de Vena25bd942008-01-30 13:33:08 +0100586 in an oops report.
Chuck Ebbert86c41832007-02-13 13:26:25 +0100587 Range: 0 - 8192
588 Default: 64
589
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590 com20020= [HW,NET] ARCnet - COM20020 chipset
Randy Dunlapa9913042005-10-23 12:57:11 -0700591 Format:
592 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593
594 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
595 Format: <io>[,<irq>]
596
Randy Dunlapa9913042005-10-23 12:57:11 -0700597 com90xx= [HW,NET]
598 ARCnet - COM90xx chipset (memory-mapped buffers)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700599 Format: <io>[,<irq>[,<memstart>]]
600
601 condev= [HW,S390] console device
602 conmode=
Randy Dunlapa9913042005-10-23 12:57:11 -0700603
Linus Torvalds1da177e2005-04-16 15:20:36 -0700604 console= [KNL] Output console device and options.
605
606 tty<n> Use the virtual console device <n>.
607
608 ttyS<n>[,options]
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800609 ttyUSB0[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700610 Use the specified serial port. The options are of
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800611 the form "bbbbpnf", where "bbbb" is the baud rate,
612 "p" is parity ("n", "o", or "e"), "n" is number of
613 bits, and "f" is flow control ("r" for RTS or
614 omit it). Default is "9600n8".
Linus Torvalds1da177e2005-04-16 15:20:36 -0700615
Jani Nikulae52347b2016-11-03 12:10:10 +0200616 See Documentation/admin-guide/serial-console.rst for more
Randy Dunlapf1a1c2d2006-03-25 03:08:17 -0800617 information. See
618 Documentation/networking/netconsole.txt for an
619 alternative.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700620
Yinghai Lu18a8bd92007-07-15 23:37:59 -0700621 uart[8250],io,<addr>[,options]
622 uart[8250],mmio,<addr>[,options]
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900623 uart[8250],mmio16,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400624 uart[8250],mmio32,<addr>[,options]
625 uart[8250],0x<addr>[,options]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700626 Start an early, polled-mode console on the 8250/16550
627 UART at the specified I/O port or MMIO address,
Peter Hurleyca782f12015-04-06 10:52:39 -0400628 switching to the matching ttyS device later.
629 MMIO inter-register address stride is either 8-bit
Masahiro Yamadabd94c402015-10-28 12:46:05 +0900630 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
631 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
632 to be equivalent to 'mmio'. 'options' are specified in
633 the same format described for ttyS above; if unspecified,
Peter Hurleyca782f12015-04-06 10:52:39 -0400634 the h/w is not re-initialized.
635
Konrad Rzeszutek Wilka2fd6412013-02-25 15:54:09 -0500636 hvc<n> Use the hypervisor console device <n>. This is for
637 both Xen and PowerPC hypervisors.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700638
Samuel Thibaultf7511d52008-04-30 00:54:51 -0700639 If the device connected to the port is not a TTY but a braille
640 device, prepend "brl," before the device type, for instance
641 console=brl,ttyS0
642 For now, only VisioBraille is supported.
643
Daniel Mackf324edc2009-06-16 15:33:52 -0700644 consoleblank= [KNL] The console blank (screen saver) timeout in
645 seconds. Defaults to 10*60 = 10mins. A value of 0
646 disables the blank timer.
647
Hidehiro Kawai4cb0e112009-01-06 14:42:47 -0800648 coredump_filter=
649 [KNL] Change the default value for
650 /proc/<pid>/coredump_filter.
651 See also Documentation/filesystems/proc.txt.
652
Len Brown62027ae2011-04-01 18:13:10 -0400653 cpuidle.off=1 [CPU_IDLE]
654 disable the cpuidle sub-system
655
Len Brownd68921f2015-05-11 17:27:09 -0400656 cpu_init_udelay=N
657 [X86] Delay for N microsec between assert and de-assert
658 of APIC INIT to start processors. This delay occurs
659 on every CPU online, such as boot, and resume from suspend.
660 Default: 10000
661
Linus Torvalds1da177e2005-04-16 15:20:36 -0700662 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
Randy Dunlapa9913042005-10-23 12:57:11 -0700663 Format:
664 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700665
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800666 crashkernel=size[KMG][@offset[KMG]]
667 [KNL] Using kexec, Linux can switch to a 'crash kernel'
668 upon panic. This parameter reserves the physical
669 memory region [offset, offset + size] for that kernel
670 image. If '@offset' is omitted, then a suitable offset
671 is selected automatically. Check
672 Documentation/kdump/kdump.txt for further details.
Eric W. Biedermandc009d92005-06-25 14:57:52 -0700673
Bernhard Wallefb391592007-10-18 23:41:02 -0700674 crashkernel=range1:size1[,range2:size2,...][@offset]
675 [KNL] Same as above, but depends on the memory
676 in the running system. The syntax of range is
677 start-[end] where start and end are both
678 a memory unit (amount[KMG]). See also
Ahmed S. Darwish6f21e642011-02-20 20:08:35 -0800679 Documentation/kdump/kdump.txt for an example.
Bernhard Wallefb391592007-10-18 23:41:02 -0700680
Yinghai Luadbc7422013-04-15 22:23:48 -0700681 crashkernel=size[KMG],high
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700682 [KNL, x86_64] range could be above 4G. Allow kernel
683 to allocate physical memory region from top, so could
684 be above 4G if system have more than 4G ram installed.
685 Otherwise memory region will be allocated below 4G, if
686 available.
687 It will be ignored if crashkernel=X is specified.
Yinghai Luadbc7422013-04-15 22:23:48 -0700688 crashkernel=size[KMG],low
689 [KNL, x86_64] range under 4G. When crashkernel=X,high
690 is passed, kernel could allocate physical memory region
Yinghai Luc729de82013-04-15 22:23:45 -0700691 above 4G, that cause second kernel crash on system
692 that require some amount of low memory, e.g. swiotlb
Baoquan Hec6045032015-09-24 16:51:25 +0800693 requires at least 64M+32K low memory, also enough extra
694 low memory is needed to make sure DMA buffers for 32-bit
695 devices won't run out. Kernel would try to allocate at
696 at least 256M below 4G automatically.
Yinghai Luc729de82013-04-15 22:23:45 -0700697 This one let user to specify own low range under 4G
698 for second kernel instead.
699 0: to disable low allocation.
Yinghai Luadbc7422013-04-15 22:23:48 -0700700 It will be ignored when crashkernel=X,high is not used
Yinghai Lu55a20ee2013-04-15 22:23:47 -0700701 or memory reserved is below 4G.
Yinghai Luc729de82013-04-15 22:23:45 -0700702
Richard W.M. Jones9e5c9fe2016-05-03 10:00:17 +0100703 cryptomgr.notests
704 [KNL] Disable crypto self-tests
705
Linus Torvalds1da177e2005-04-16 15:20:36 -0700706 cs89x0_dma= [HW,NET]
707 Format: <dma>
708
709 cs89x0_media= [HW,NET]
710 Format: { rj45 | aui | bnc }
Randy Dunlapa9913042005-10-23 12:57:11 -0700711
Randy Dunlapa9913042005-10-23 12:57:11 -0700712 dasd= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700713 See header of drivers/s390/block/dasd_devmap.c.
714
715 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
716 (one device per port)
717 Format: <port#>,<type>
718 See also Documentation/input/joystick-parport.txt
719
Thomas Renningera648ec02010-08-06 16:11:02 +0200720 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
721 time. See Documentation/dynamic-debug-howto.txt for
Jim Cromie29e36c92012-04-27 14:30:41 -0600722 details. Deprecated, see dyndbg.
Thomas Renningera648ec02010-08-06 16:11:02 +0200723
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724 debug [KNL] Enable kernel debugging (events log level).
725
Ingo Molnarcae2ed92006-07-03 00:24:48 -0700726 debug_locks_verbose=
727 [KNL] verbose self-tests
728 Format=<0|1>
729 Print debugging info while doing the locking API
730 self-tests.
731 We default to 0 (no extra messages), setting it to
732 1 will print _a lot_ more information - normally
733 only useful to kernel developers.
734
Thomas Gleixner3ac7fe52008-04-30 00:55:01 -0700735 debug_objects [KNL] Enable object debugging
736
Kyle McMartin3e8ebb52009-03-01 20:41:41 -0500737 no_debug_objects
738 [KNL] Disable object debugging
739
Stanislaw Gruszkac0a32fc2012-01-10 15:07:28 -0800740 debug_guardpage_minorder=
741 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
742 parameter allows control of the order of pages that will
743 be intentionally kept free (and hence protected) by the
744 buddy allocator. Bigger value increase the probability
745 of catching random memory corruption, but reduce the
746 amount of memory for normal system use. The maximum
747 possible value is MAX_ORDER/2. Setting this parameter
748 to 1 or 2 should be enough to identify most random
749 memory corruption problems caused by bugs in kernel or
750 driver code when a CPU writes to (or reads from) a
751 random memory location. Note that there exists a class
752 of memory corruptions problems caused by buggy H/W or
753 F/W or by drivers badly programing DMA (basically when
754 memory is written at bus level and the CPU MMU is
755 bypassed) which are not detectable by
756 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
757 tracking down these problems.
758
Joonsoo Kim031bc572014-12-12 16:55:52 -0800759 debug_pagealloc=
760 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
761 parameter enables the feature at boot time. In
762 default, it is disabled. We can avoid allocating huge
763 chunk of memory for debug pagealloc if we don't enable
764 it at boot time and the system will work mostly same
765 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
766 on: enable the feature
767
Thomas Gleixnerd3af01f2008-07-15 15:04:56 +0200768 debugpat [X86] Enable PAT debugging
769
Robert P. J. Day2d27a962008-02-03 15:18:45 +0200770 decnet.addr= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700771 Format: <area>[,<node>]
772 See also Documentation/networking/decnet.txt.
773
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700774 default_hugepagesz=
775 [same as hugepagesz=] The size of the default
776 HugeTLB page size. This is the size represented by
777 the legacy /proc/ hugepages APIs, used for SHM, and
778 default size when mounting hugetlbfs filesystems.
779 Defaults to the default architecture's huge page size
780 if not specified.
Antonino A. Daplas55ff9782007-05-08 00:38:53 -0700781
Linus Torvalds1da177e2005-04-16 15:20:36 -0700782 dhash_entries= [KNL]
783 Set number of hash buckets for dentry cache.
Randy Dunlapa9913042005-10-23 12:57:11 -0700784
Oliver O'Halloranfaf78822016-07-05 11:43:21 +1000785 disable_1tb_segments [PPC]
786 Disables the use of 1TB hash page table segments. This
787 causes the kernel to fall back to 256MB segments which
788 can be useful when debugging issues that require an SLB
789 miss to occur.
790
Brian Haleyb0f83b22010-02-04 13:36:50 -0800791 disable= [IPV6]
792 See Documentation/networking/ipv6.txt.
793
Aneesh Kumar K.Vb275bfb2016-07-13 15:05:31 +0530794 disable_radix [PPC]
795 Disable RADIX MMU mode on POWER9
796
HATAYAMA Daisuke151e0c72014-01-15 15:44:58 +0900797 disable_cpu_apicid= [X86,APIC,SMP]
798 Format: <int>
799 The number of initial APIC ID for the
800 corresponding CPU to be disabled at boot,
801 mostly used for the kdump 2nd kernel to
802 disable BSP to wake up multiple CPUs without
803 causing system reset or hang due to sending
804 INIT from AP to BSP.
805
Nishanth Aravamudan4e8b0cf2011-02-10 09:10:47 +0000806 disable_ddw [PPC/PSERIES]
807 Disable Dynamic DMA Window support. Use this if
808 to workaround buggy firmware.
809
Brian Haleyb0f83b22010-02-04 13:36:50 -0800810 disable_ipv6= [IPV6]
811 See Documentation/networking/ipv6.txt.
812
Yinghai Lu95ffa242008-04-29 03:52:33 -0700813 disable_mtrr_cleanup [X86]
Yinghai Lu95ffa242008-04-29 03:52:33 -0700814 The kernel tries to adjust MTRR layout from continuous
815 to discrete, to make X server driver able to add WB
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700816 entry later. This parameter disables that.
Yinghai Lu95ffa242008-04-29 03:52:33 -0700817
Yinghai Lu093af8d2008-01-30 13:33:32 +0100818 disable_mtrr_trim [X86, Intel and AMD only]
Jesse Barnes99fc8d42008-01-30 13:33:18 +0100819 By default the kernel will trim any uncacheable
820 memory out of your available memory pool based on
821 MTRR settings. This parameter disables that behavior,
822 possibly causing your machine to run very slowly.
823
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +0530824 disable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700825 Disable PIN 1 of APIC timer
826 Can be useful to work around chipset bugs.
827
Prarit Bhargavace14c582015-08-25 13:34:53 -0400828 dis_ucode_ldr [X86] Disable the microcode loader.
829
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700830 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
831 this option disables the debugging code at boot.
832
833 dma_debug_entries=<number>
834 This option allows to tune the number of preallocated
835 entries for DMA-API debugging code. One entry is
836 required per DMA-API allocation. Use this if the
837 DMA-API debugging code disables itself because the
838 architectural default is too low.
839
Joerg Roedel1745de52009-05-22 21:49:51 +0200840 dma_debug_driver=<driver_name>
841 With this option the DMA-API debugging driver
842 filter feature can be enabled at boot time. Just
843 pass the driver to filter for as the parameter.
844 The filter can be disabled or changed to another
845 driver later using sysfs.
846
Bob Paauwe96206e22015-08-27 10:04:13 -0700847 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
848 Broken monitors, graphic adapters, KVMs and EDIDless
849 panels may send no or incorrect EDID data sets.
850 This parameter allows to specify an EDID data sets
851 in the /lib/firmware directory that are used instead.
Carsten Emdeda0df922012-03-18 22:37:33 +0100852 Generic built-in EDID data sets are used, if one of
853 edid/1024x768.bin, edid/1280x1024.bin,
854 edid/1680x1050.bin, or edid/1920x1080.bin is given
855 and no file with the same name exists. Details and
856 instructions how to build your own EDID data are
857 available in Documentation/EDID/HOWTO.txt. An EDID
858 data set will only be used for a particular connector,
859 if its name and a colon are prepended to the EDID
Bob Paauwe96206e22015-08-27 10:04:13 -0700860 name. Each connector may use a unique EDID data
861 set by separating the files with a comma. An EDID
862 data set with no connector name will be used for
863 any connectors not explicitly specified.
Carsten Emdeda0df922012-03-18 22:37:33 +0100864
Linus Torvalds1da177e2005-04-16 15:20:36 -0700865 dscc4.setup= [NET]
866
Lukas Wunner58c54752016-11-12 21:32:36 +0000867 dump_apple_properties [X86]
868 Dump name and content of EFI device properties on
869 x86 Macs. Useful for driver authors to determine
870 what data is available or for reverse-engineering.
871
Jim Cromie29e36c92012-04-27 14:30:41 -0600872 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
873 module.dyndbg[="val"]
874 Enable debug messages at boot time. See
875 Documentation/dynamic-debug-howto.txt for details.
876
Dave Hansen8c3641e2015-06-07 11:37:02 -0700877 nompx [X86] Disables Intel Memory Protection Extensions.
878 See Documentation/x86/intel_mpx.txt for more
879 information about the feature.
880
Dave Hansen06976942016-02-12 13:02:29 -0800881 nopku [X86] Disable Memory Protection Keys CPU feature found
882 in some Intel CPUs.
883
Luis R. Rodriguezf2411da2015-03-30 16:20:05 -0700884 module.async_probe [KNL]
885 Enable asynchronous probe on this module.
886
Mark Salter56aeeba2014-04-07 15:39:53 -0700887 early_ioremap_debug [KNL]
888 Enable debug messages in early_ioremap support. This
889 is useful for tracking down temporary early mappings
890 which are not unmapped.
891
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700892 earlycon= [KNL] Output early console device and options.
Rob Herring0d3c6732014-04-18 17:19:57 -0500893
Scott Wood5664f762015-09-14 19:54:07 -0500894 When used with no options, the early console is
895 determined by the stdout-path property in device
896 tree's chosen node.
897
Scott Telfordc41251b2016-09-22 16:58:16 +0100898 cdns,<addr>[,options]
899 Start an early, polled-mode console on a Cadence
900 (xuartps) serial port at the specified address. Only
901 supported option is baud rate. If baud rate is not
902 specified, the serial port must already be setup and
903 configured.
Michal Simek6fa62fc2014-09-10 12:43:02 +0200904
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700905 uart[8250],io,<addr>[,options]
906 uart[8250],mmio,<addr>[,options]
Samium Gromoff1917ac72010-07-20 15:26:51 -0700907 uart[8250],mmio32,<addr>[,options]
Noam Camus6e63be32015-05-25 06:54:28 +0300908 uart[8250],mmio32be,<addr>[,options]
Peter Hurleyca782f12015-04-06 10:52:39 -0400909 uart[8250],0x<addr>[,options]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700910 Start an early, polled-mode console on the 8250/16550
911 UART at the specified I/O port or MMIO address.
Randy Dunlap16290242011-08-13 12:34:52 -0700912 MMIO inter-register address stride is either 8-bit
Noam Camus6e63be32015-05-25 06:54:28 +0300913 (mmio) or 32-bit (mmio32 or mmio32be).
914 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
915 to be equivalent to 'mmio'. 'options' are specified
916 in the same format described for "console=ttyS<n>"; if
Peter Hurleyca782f12015-04-06 10:52:39 -0400917 unspecified, the h/w is not initialized.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -0700918
Rob Herring0d3c6732014-04-18 17:19:57 -0500919 pl011,<addr>
Timur Tabi3b78fae2016-01-04 15:37:42 -0600920 pl011,mmio32,<addr>
Rob Herring0d3c6732014-04-18 17:19:57 -0500921 Start an early, polled-mode console on a pl011 serial
922 port at the specified address. The pl011 serial port
923 must already be setup and configured. Options are not
Timur Tabi3b78fae2016-01-04 15:37:42 -0600924 yet supported. If 'mmio32' is specified, then only
925 the driver will use only 32-bit accessors to read/write
926 the device registers.
Rob Herring0d3c6732014-04-18 17:19:57 -0500927
Andreas Färber736d5532016-03-06 12:21:24 +0100928 meson,<addr>
929 Start an early, polled-mode console on a meson serial
930 port at the specified address. The serial port must
931 already be setup and configured. Options are not yet
932 supported.
933
Stephen Boyd0efe7292014-09-15 17:22:51 -0700934 msm_serial,<addr>
935 Start an early, polled-mode console on an msm serial
936 port at the specified address. The serial port
937 must already be setup and configured. Options are not
938 yet supported.
939
940 msm_serial_dm,<addr>
941 Start an early, polled-mode console on an msm serial
942 dm port at the specified address. The serial port
943 must already be setup and configured. Options are not
944 yet supported.
945
Rob Herringd50d7262014-04-18 17:19:58 -0500946 smh Use ARM semihosting calls for early console.
947
Tomasz Figab94ba032015-01-23 14:47:41 +0100948 s3c2410,<addr>
949 s3c2412,<addr>
950 s3c2440,<addr>
951 s3c6400,<addr>
952 s5pv210,<addr>
953 exynos4210,<addr>
954 Use early console provided by serial driver available
955 on Samsung SoCs, requires selecting proper type and
956 a correct base address of the selected UART port. The
957 serial port must already be setup and configured.
958 Options are not yet supported.
959
Martin Blumenstinglec84aa02016-12-11 21:42:23 +0100960 lantiq,<addr>
961 Start an early, polled-mode console on a lantiq serial
962 (lqasc) port at the specified address. The serial port
963 must already be setup and configured. Options are not
964 yet supported.
965
Stefan Agner1d59b382015-10-17 00:45:55 -0700966 lpuart,<addr>
967 lpuart32,<addr>
968 Use early console provided by Freescale LP UART driver
969 found on Freescale Vybrid and QorIQ LS1021A processors.
970 A valid base address must be provided, and the serial
971 port must already be setup and configured.
972
Wilson Ding30530792016-02-16 19:14:53 +0100973 armada3700_uart,<addr>
974 Start an early, polled-mode console on the
975 Armada 3700 serial port at the specified
976 address. The serial port must already be setup
977 and configured. Options are not yet supported.
978
Heiko Carstens89175cf2017-01-11 09:14:52 +0100979 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k,S390]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700980 earlyprintk=vga
Matt Fleming72548e82013-10-04 09:36:56 +0100981 earlyprintk=efi
Heiko Carstens89175cf2017-01-11 09:14:52 +0100982 earlyprintk=sclp
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -0500983 earlyprintk=xen
Linus Torvalds1da177e2005-04-16 15:20:36 -0700984 earlyprintk=serial[,ttySn[,baudrate]]
Dave Hansen147ea092013-04-10 14:03:38 -0700985 earlyprintk=serial[,0x...[,baudrate]]
Jason Wesselea3acb12009-09-24 09:08:30 -0500986 earlyprintk=ttySn[,baudrate]
Jason Wessel9780bc42009-08-20 15:39:57 -0500987 earlyprintk=dbgp[debugController#]
Alexander Kuleshovc43088e2015-06-10 23:21:15 +0600988 earlyprintk=pciserial,bus:device.function[,baudrate]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700989
Dave Hansen147ea092013-04-10 14:03:38 -0700990 earlyprintk is useful when the kernel crashes before
991 the normal console is initialized. It is not enabled by
992 default because it has some cosmetic problems.
993
Randy Dunlapa9913042005-10-23 12:57:11 -0700994 Append ",keep" to not disable it when the real console
Linus Torvalds1da177e2005-04-16 15:20:36 -0700995 takes over.
996
Matt Fleming72548e82013-10-04 09:36:56 +0100997 Only one of vga, efi, serial, or usb debug port can
998 be used at a time.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700999
Dave Hansen147ea092013-04-10 14:03:38 -07001000 Currently only ttyS0 and ttyS1 may be specified by
1001 name. Other I/O ports may be explicitly specified
1002 on some architectures (x86 and arm at least) by
1003 replacing ttySn with an I/O port address, like this:
1004 earlyprintk=serial,0x1008,115200
1005 You can find the port for a given device in
1006 /proc/tty/driver/serial:
1007 2: uart:ST16650V2 port:00001008 irq:18 ...
Linus Torvalds1da177e2005-04-16 15:20:36 -07001008
1009 Interaction with the standard serial driver is not
1010 very good.
1011
Matt Fleming72548e82013-10-04 09:36:56 +01001012 The VGA and EFI output is eventually overwritten by
1013 the real console.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014
Konrad Rzeszutek Wilk2482a922013-02-25 15:54:08 -05001015 The xen output can only be used by Xen PV guests.
1016
Heiko Carstens89175cf2017-01-11 09:14:52 +01001017 The sclp output can only be used on s390.
1018
Chen, Gongc700f012013-12-06 01:17:08 -05001019 edac_report= [HW,EDAC] Control how to report EDAC event
1020 Format: {"on" | "off" | "force"}
1021 on: enable EDAC to report H/W event. May be overridden
1022 by other higher priority error reporting module.
1023 off: disable H/W event reporting through EDAC.
1024 force: enforce the use of EDAC to report H/W event.
1025 default: on.
1026
Jason Wessel97311912010-05-20 21:04:30 -05001027 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1028 ekgdboc=kbd
1029
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001030 This is designed to be used in conjunction with
Jason Wessel97311912010-05-20 21:04:30 -05001031 the boot argument: earlyprintk=vga
1032
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033 edd= [EDD]
Tim Gardner8c4dd602008-04-29 01:02:45 -07001034 Format: {"off" | "on" | "skip[mbr]"}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001035
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001036 efi= [EFI]
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001037 Format: { "old_map", "nochunk", "noruntime", "debug" }
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001038 old_map [X86-64]: switch to the old ioremap-based EFI
1039 runtime services mapping. 32-bit still uses this one by
1040 default.
Matt Fleming5a17dae2014-08-05 11:52:11 +01001041 nochunk: disable reading files in "chunks" in the EFI
1042 boot stub, as chunking can cause problems with some
1043 firmware implementations.
Dave Young5ae36832014-08-14 17:15:28 +08001044 noruntime : disable EFI runtime services support
Borislav Petkovfed6cef2015-02-05 11:44:41 +01001045 debug: enable misc debug output
Borislav Petkovd2f7cbe2013-10-31 17:25:08 +01001046
Richard Weinberger8c58bf32013-04-17 01:00:53 +02001047 efi_no_storage_paranoia [EFI; X86]
1048 Using this parameter you can use more than 50% of
1049 your efi variable storage. Use this parameter only if
1050 you are really sure that your UEFI does sane gc and
1051 fulfills the spec otherwise your board may brick.
1052
Taku Izumi0f96a992015-09-30 23:01:56 +09001053 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1054 Add arbitrary attribute to specific memory range by
1055 updating original EFI memory map.
1056 Region of memory which aa attribute is added to is
1057 from ss to ss+nn.
1058 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1059 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1060 attribute is added to range 0x100000000-0x180000000 and
1061 0x10a0000000-0x1120000000.
1062
1063 Using this parameter you can do debugging of EFI memmap
1064 related feature. For example, you can do debugging of
1065 Address Range Mirroring feature even if your box
1066 doesn't support it.
1067
Octavian Purdila475fb4e2016-07-08 19:13:12 +03001068 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1069 that is to be dynamically loaded by Linux. If there are
1070 multiple variables with the same name but with different
1071 vendor GUIDs, all of them will be loaded. See
1072 Documentation/acpi/ssdt-overlays.txt for details.
1073
1074
Linus Torvalds1da177e2005-04-16 15:20:36 -07001075 eisa_irq_edge= [PARISC,HW]
1076 See header of drivers/parisc/eisa.c.
1077
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001078 elanfreq= [X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001079 See comment before function elanfreq_setup() in
Pavel Machek71f77052008-07-04 09:59:43 -07001080 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001081
1082 elevator= [IOSCHED]
Randy Dunlap17a9e7b2010-11-11 12:09:59 +01001083 Format: {"cfq" | "deadline" | "noop"}
Paul Bolle395cf962011-08-15 02:02:26 +02001084 See Documentation/block/cfq-iosched.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07001085 Documentation/block/deadline-iosched.txt for details.
1086
Michael Holzheud3bf37952011-10-30 15:16:37 +01001087 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
Randy Dunlapa9913042005-10-23 12:57:11 -07001088 Specifies physical address of start of kernel core
Michael Holzheud3bf37952011-10-30 15:16:37 +01001089 image elf header and optionally the size. Generally
1090 kexec loader will pass this option to capture kernel.
Vivek Goyalaac04b32006-01-09 20:51:47 -08001091 See Documentation/kdump/kdump.txt for details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001092
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001093 enable_mtrr_cleanup [X86]
1094 The kernel tries to adjust MTRR layout from continuous
1095 to discrete, to make X server driver able to add WB
1096 entry later. This parameter enables that.
1097
Randy Dunlapca1eda22009-05-06 16:02:58 -07001098 enable_timer_pin_1 [X86]
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001099 Enable PIN 1 of APIC timer
1100 Can be useful to work around chipset bugs
1101 (in particular on some ATI chipsets).
1102 The kernel tries to set a reasonable default.
1103
Linus Torvalds1da177e2005-04-16 15:20:36 -07001104 enforcing [SELINUX] Set initial enforcing status.
1105 Format: {"0" | "1"}
1106 See security/selinux/Kconfig help text.
1107 0 -- permissive (log only, no denials).
1108 1 -- enforcing (deny and log).
1109 Default value is 0.
1110 Value can be changed at runtime via /selinux/enforce.
1111
Huang Yinga08f82d2010-05-18 14:35:21 +08001112 erst_disable [ACPI]
1113 Disable Error Record Serialization Table (ERST)
1114 support.
1115
Linus Torvalds1da177e2005-04-16 15:20:36 -07001116 ether= [HW,NET] Ethernet cards parameters
1117 This option is obsoleted by the "netdev=" option, which
1118 has equivalent usage. See its documentation for details.
1119
Mimi Zohar7102ebc2011-05-12 18:33:20 -04001120 evm= [EVM]
1121 Format: { "fix" }
1122 Permit 'security.evm' to be updated regardless of
1123 current integrity status.
1124
Akinobu Mitade1ba092006-12-08 02:39:42 -08001125 failslab=
1126 fail_page_alloc=
1127 fail_make_request=[KNL]
1128 General fault injection mechanism.
1129 Format: <interval>,<probability>,<space>,<times>
Paul Bolle395cf962011-08-15 02:02:26 +02001130 See also Documentation/fault-injection/.
Akinobu Mitade1ba092006-12-08 02:39:42 -08001131
Linus Torvalds1da177e2005-04-16 15:20:36 -07001132 floppy= [HW]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001133 See Documentation/blockdev/floppy.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001134
Alex Chiangf13ae302008-05-08 14:03:23 -06001135 force_pal_cache_flush
1136 [IA-64] Avoid check_sal_cache_flush which may hang on
1137 buggy SAL_CACHE_FLUSH implementations. Using this
1138 parameter will force ia64_sal_cache_flush to call
1139 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1140
Chris Bainbridge69f23662014-03-07 18:40:42 +07001141 forcepae [X86-32]
1142 Forcefully enable Physical Address Extension (PAE).
1143 Many Pentium M systems disable PAE but may have a
1144 functionally usable PAE implementation.
1145 Warning: use of this parameter will taint the kernel
1146 and may cause unknown problems.
1147
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001148 ftrace=[tracer]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001149 [FTRACE] will set and start the specified tracer
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001150 as early as possible in order to facilitate early
1151 boot debugging.
1152
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001153 ftrace_dump_on_oops[=orig_cpu]
Steven Rostedt2af15d62009-05-28 13:37:24 -04001154 [FTRACE] will dump the trace buffers on oops.
Frederic Weisbeckercecbca92010-04-18 19:08:41 +02001155 If no parameter is passed, ftrace will dump
1156 buffers of all CPUs, but if you pass orig_cpu, it will
1157 dump only the buffer of the CPU that triggered the
1158 oops.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001159
1160 ftrace_filter=[function-list]
1161 [FTRACE] Limit the functions traced by the function
1162 tracer at boot up. function-list is a comma separated
1163 list of functions. This list can be changed at run
1164 time by the set_ftrace_filter file in the debugfs
Randy Dunlap16290242011-08-13 12:34:52 -07001165 tracing directory.
Steven Rostedt2af15d62009-05-28 13:37:24 -04001166
1167 ftrace_notrace=[function-list]
1168 [FTRACE] Do not trace the functions specified in
1169 function-list. This list can be changed at run time
1170 by the set_ftrace_notrace file in the debugfs
1171 tracing directory.
Peter Zijlstrad9e54072008-11-01 19:57:37 +01001172
Stefan Assmann369bc182009-10-12 22:17:21 +02001173 ftrace_graph_filter=[function-list]
1174 [FTRACE] Limit the top level callers functions traced
1175 by the function graph tracer at boot up.
1176 function-list is a comma separated list of functions
1177 that can be changed at run time by the
1178 set_graph_function file in the debugfs tracing directory.
1179
Namhyung Kim0d7d9a12014-06-13 01:23:50 +09001180 ftrace_graph_notrace=[function-list]
1181 [FTRACE] Do not trace from the functions specified in
1182 function-list. This list is a comma separated list of
1183 functions that can be changed at run time by the
1184 set_graph_notrace file in the debugfs tracing directory.
1185
Linus Torvalds1da177e2005-04-16 15:20:36 -07001186 gamecon.map[2|3]=
1187 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1188 support via parallel port (up to 5 devices per port)
1189 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1190 See also Documentation/input/joystick-parport.txt
1191
1192 gamma= [HW,DRM]
1193
Yinghai Luaaf23042008-01-30 13:33:09 +01001194 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1195 Format: off | on
1196 default: on
1197
Peter Oberparleiter2521f2c2009-06-17 16:28:08 -07001198 gcov_persist= [GCOV] When non-zero (default), profiling data for
1199 kernel modules is saved and remains accessible via
1200 debugfs, even when the module is unloaded/reloaded.
1201 When zero, profiling data is discarded and associated
1202 debugfs files are removed at module unload time.
1203
Thomas Gleixner47512cf2017-02-15 11:11:50 +01001204 goldfish [X86] Enable the goldfish android emulator platform.
1205 Don't use this when you are not running on the
1206 android emulator
1207
Linus Torvalds1da177e2005-04-16 15:20:36 -07001208 gpt [EFI] Forces disk with valid GPT signature but
Davidlohr Bueso6c5de792014-01-23 15:56:03 -08001209 invalid Protective MBR to be treated as GPT. If the
1210 primary GPT is corrupted, it enables the backup/alternate
1211 GPT to be used instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001212
Andreas Larsson6cec9b02012-11-15 08:47:14 +01001213 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1214 the "Enable 0" bit of the configuration register.
1215 Format: 0 | 1
1216 Default: 0
1217 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1218 the "Enable 0" bit of the configuration register.
1219 Format: 0 | 1
1220 Default: 0
1221 grcan.select= [HW] Select which physical interface to use.
1222 Format: 0 | 1
1223 Default: 0
1224 grcan.txsize= [HW] Sets the size of the tx buffer.
1225 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1226 Default: 1024
1227 grcan.rxsize= [HW] Sets the size of the rx buffer.
1228 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1229 Default: 1024
1230
Bamvor Jian Zhang0f98dd12016-08-31 11:45:46 +02001231 gpio-mockup.gpio_mockup_ranges
1232 [HW] Sets the ranges of gpiochip of for this device.
1233 Format: <start1>,<end1>,<start2>,<end2>...
1234
Jiri Kosina55537872015-11-05 18:44:41 -08001235 hardlockup_all_cpu_backtrace=
1236 [KNL] Should the hard-lockup detector generate
1237 backtraces on all cpus.
1238 Format: <integer>
1239
Linus Torvalds1da177e2005-04-16 15:20:36 -07001240 hashdist= [KNL,NUMA] Large hashes allocated during boot
1241 are distributed across NUMA nodes. Defaults on
Randy Dunlap16290242011-08-13 12:34:52 -07001242 for 64-bit NUMA, off otherwise.
Randy Dunlapa9913042005-10-23 12:57:11 -07001243 Format: 0 | 1 (for off | on)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001244
1245 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1246
1247 hd= [EIDE] (E)IDE hard drive subsystem geometry
1248 Format: <cyl>,<head>,<sect>
1249
Huang Yingea8c0712010-05-18 14:35:15 +08001250 hest_disable [ACPI]
1251 Disable Hardware Error Source Table (HEST) support;
1252 corresponding firmware-first mode error processing
1253 logic will be disabled.
1254
Linus Torvalds1da177e2005-04-16 15:20:36 -07001255 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1256 size of <nn>. This works even on boxes that have no
1257 highmem otherwise. This also works to reduce highmem
1258 size on bigger boxes.
1259
Thomas Gleixner54cdfdb2007-02-16 01:28:11 -08001260 highres= [KNL] Enable/disable high resolution timer mode.
1261 Valid parameters: "on", "off"
1262 Default: "on"
1263
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264 hisax= [HW,ISDN]
1265 See Documentation/isdn/README.HiSax.
1266
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001267 hlt [BUGS=ARM,SH]
1268
1269 hpet= [X86-32,HPET] option to control HPET usage
1270 Format: { enable (default) | disable | force |
1271 verbose }
1272 disable: disable HPET and use PIT instead
1273 force: allow force enabled of undocumented chips (ICH4,
1274 VIA, nVidia)
1275 verbose: show contents of HPET registers during setup
1276
Prarit Bhargava3d035f52013-11-12 15:08:33 -08001277 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1278 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1279
Andi Kleenb4718e62008-07-23 21:27:51 -07001280 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1281 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
Jon Tollefson0d9ea752008-07-23 21:27:56 -07001282 On x86-64 and powerpc, this option can be specified
1283 multiple times interleaved with hugepages= to reserve
1284 huge pages of different sizes. Valid pages sizes on
1285 x86-64 are 2M (when the CPU supports "pse") and 1G
Luiz Capitulino27ec26e2014-12-12 16:55:18 -08001286 (when the CPU supports the "pdpe1gb" cpuinfo flag).
Paul Mundt6902aa82008-09-21 17:14:42 +09001287
Hendrik Brueckner555d61d2009-01-09 12:15:02 +01001288 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1289 terminal devices. Valid values: 0..8
Hendrik Brueckner431429f2009-03-26 15:23:55 +01001290 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1291 If specified, z/VM IUCV HVC accepts connections
1292 from listed z/VM user IDs only.
Hendrik Bruecknercef71252008-12-25 13:39:55 +01001293
James Hoganfdabf522012-10-09 11:00:27 +01001294 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1295 hardware thread id mappings.
1296 Format: <cpu>:<hwthread>
1297
Fabio M. Di Nitto7bf69392011-03-22 16:34:20 -07001298 keep_bootcon [KNL]
1299 Do not unregister boot console at start. This is only
1300 useful for debugging when something happens in the window
1301 between unregistering the boot console and initializing
1302 the real console.
1303
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001304 i2c_bus= [HW] Override the default board specific I2C bus speed
Jarkko Nikula79547632009-03-23 18:07:48 -07001305 or register an additional I2C bus that is not
1306 registered from board initialization code.
Jarkko Nikula3a853fb2009-03-23 18:07:47 -07001307 Format:
1308 <bus_id>,<clkrate>
1309
Jiri Kosina36d95732008-10-06 02:51:09 -04001310 i8042.debug [HW] Toggle i8042 debug mode
Stephen Chandler Paule1443d22015-07-15 10:20:17 -07001311 i8042.unmask_kbd_data
1312 [HW] Enable printing of interrupt data from the KBD port
1313 (disabled by default, and as a pre-condition
1314 requires that i8042.debug=1 be enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001315 i8042.direct [HW] Put keyboard port into non-translated mode
Matt LaPlante84eb8d02006-10-03 22:53:09 +02001316 i8042.dumbkbd [HW] Pretend that controller can only read data from
1317 keyboard and cannot control its state
Linus Torvalds1da177e2005-04-16 15:20:36 -07001318 (Don't attempt to blink the leds)
1319 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
Dmitry Torokhov945ef0d2005-09-04 01:42:00 -05001320 i8042.nokbd [HW] Don't check/create keyboard port
Jiri Kosina75d08c72008-03-13 16:13:59 -04001321 i8042.noloop [HW] Disable the AUX Loopback command while probing
1322 for the AUX port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001323 i8042.nomux [HW] Don't check presence of an active multiplexing
Dmitry Torokhove55a3362014-10-31 09:35:53 -07001324 controller
Linus Torvalds1da177e2005-04-16 15:20:36 -07001325 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1326 controllers
Masanari Iida24775d62012-02-15 00:26:42 +09001327 i8042.notimeout [HW] Ignore timeout condition signalled by controller
Marcos Paulo de Souza930e1922016-10-01 12:07:35 -07001328 i8042.reset [HW] Reset the controller during init, cleanup and
1329 suspend-to-ram transitions, only during s2r
1330 transitions, or never reset
1331 Format: { 1 | Y | y | 0 | N | n }
1332 1, Y, y: always reset controller
1333 0, N, n: don't ever reset controller
1334 Default: only on s2r transitions on x86; most other
1335 architectures force reset to be always executed
Linus Torvalds1da177e2005-04-16 15:20:36 -07001336 i8042.unlock [HW] Unlock (ignore) the keylock
Srihari Vijayaraghavan148e9a72015-01-07 16:25:53 -08001337 i8042.kbdreset [HW] Reset device connected to KBD port
Linus Torvalds1da177e2005-04-16 15:20:36 -07001338
1339 i810= [HW,DRM]
1340
Dmitry Torokhove70c9d52005-06-25 14:54:25 -07001341 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1342 indicates that the driver is running on unsupported
1343 hardware.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1345 does not match list of supported models.
1346 i8k.power_status
1347 [HW] Report power status in /proc/i8k
1348 (disabled by default)
1349 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1350 capability is set.
1351
Carsten Emde4dca20e2012-03-15 15:56:26 +01001352 i915.invert_brightness=
Carsten Emde7bd90902012-03-15 15:56:25 +01001353 [DRM] Invert the sense of the variable that is used to
1354 set the brightness of the panel backlight. Normally a
Carsten Emde4dca20e2012-03-15 15:56:26 +01001355 brightness value of 0 indicates backlight switched off,
1356 and the maximum of the brightness value sets the backlight
1357 to maximum brightness. If this parameter is set to 0
1358 (default) and the machine requires it, or this parameter
1359 is set to 1, a brightness value of 0 sets the backlight
1360 to maximum brightness, and the maximum of the brightness
1361 value switches the backlight off.
1362 -1 -- never invert brightness
1363 0 -- machine default
1364 1 -- force brightness inversion
Carsten Emde7bd90902012-03-15 15:56:25 +01001365
Linus Torvalds1da177e2005-04-16 15:20:36 -07001366 icn= [HW,ISDN]
1367 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1368
David Fries0af80c02009-02-25 20:28:21 +01001369 ide-core.nodma= [HW] (E)IDE subsystem
1370 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
Bartlomiej Zolnierkiewicz075affc2009-06-07 13:52:52 +02001371 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1372 .cdrom .chs .ignore_cable are additional options
Randy Dunlap1c10e932008-03-07 21:53:50 +01001373 See Documentation/ide/ide.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001374
Maciej W. Rozycki0f8b7f52014-10-25 17:03:52 +01001375 ide-generic.probe-mask= [HW] (E)IDE subsystem
1376 Format: <int>
1377 Probe mask for legacy ISA IDE ports. Depending on
1378 platform up to 6 ports are supported, enabled by
1379 setting corresponding bits in the mask to 1. The
1380 default value is 0x0, which has a special meaning.
1381 On systems that have PCI, it triggers scanning the
1382 PCI bus for the first and the second port, which
1383 are then probed. On systems without PCI the value
1384 of 0x0 enables probing the two first ports as if it
1385 was 0x3.
1386
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001387 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1388 Claim all unknown PCI IDE storage controllers.
1389
Andi Kleenf039b752007-05-02 19:27:12 +02001390 idle= [X86]
Len Brown69fb3672013-02-10 01:38:39 -05001391 Format: idle=poll, idle=halt, idle=nomwait
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001392 Poll forces a polling idle loop that can slightly
1393 improve the performance of waking up a idle CPU, but
1394 will use a lot of power and make the system run hot.
1395 Not recommended.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001396 idle=halt: Halt is forced to be used for CPU idle.
Zhao Yakuic1e3b372008-06-24 17:58:53 +08001397 In such case C2/C3 won't be used again.
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001398 idle=nomwait: Disable mwait for CPU C-states
Randy Dunlapa9913042005-10-23 12:57:11 -07001399
Maciej W. Rozycki503943e2015-11-13 00:48:29 +00001400 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1401 Format: { strict | legacy | 2008 | relaxed }
1402 Default: strict
1403
1404 Choose which programs will be accepted for execution
1405 based on the IEEE 754 NaN encoding(s) supported by
1406 the FPU and the NaN encoding requested with the value
1407 of an ELF file header flag individually set by each
1408 binary. Hardware implementations are permitted to
1409 support either or both of the legacy and the 2008 NaN
1410 encoding mode.
1411
1412 Available settings are as follows:
1413 strict accept binaries that request a NaN encoding
1414 supported by the FPU
1415 legacy only accept legacy-NaN binaries, if supported
1416 by the FPU
1417 2008 only accept 2008-NaN binaries, if supported
1418 by the FPU
1419 relaxed accept any binaries regardless of whether
1420 supported by the FPU
1421
1422 The FPU emulator is always able to support both NaN
1423 encodings, so if no FPU hardware is present or it has
1424 been disabled with 'nofpu', then the settings of
1425 'legacy' and '2008' strap the emulator accordingly,
1426 'relaxed' straps the emulator for both legacy-NaN and
1427 2008-NaN, whereas 'strict' enables legacy-NaN only on
1428 legacy processors and both NaN encodings on MIPS32 or
1429 MIPS64 CPUs.
1430
1431 The setting for ABS.fmt/NEG.fmt instruction execution
1432 mode generally follows that for the NaN encoding,
1433 except where unsupported by hardware.
1434
Ingo Molnar792908222006-12-06 20:40:51 -08001435 ignore_loglevel [KNL]
1436 Ignore loglevel setting - this will print /all/
1437 kernel messages to the console. Useful for debugging.
Yanmin Zhang0eca6b72011-10-31 17:11:25 -07001438 We also add it as printk module parameter, so users
1439 could change it dynamically, usually by
1440 /sys/module/printk/parameters/ignore_loglevel.
Ingo Molnar792908222006-12-06 20:40:51 -08001441
Konstantin Khlebnikovd977d562016-02-02 16:57:43 -08001442 ignore_rlimit_data
1443 Ignore RLIMIT_DATA setting for data mappings,
1444 print warning at first misuse. Can be changed via
1445 /sys/module/kernel/parameters/ignore_rlimit_data.
1446
Linus Torvalds1da177e2005-04-16 15:20:36 -07001447 ihash_entries= [KNL]
1448 Set number of hash buckets for inode cache.
1449
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001450 ima_appraise= [IMA] appraise integrity measurements
Dmitry Kasatkin2faa6ef2014-05-08 13:11:29 +03001451 Format: { "off" | "enforce" | "fix" | "log" }
Mimi Zohar2fe5d6d2012-02-13 10:15:05 -05001452 default: "enforce"
1453
Mimi Zohar07f6a792011-03-09 22:25:48 -05001454 ima_appraise_tcb [IMA]
1455 The builtin appraise policy appraises all files
1456 owned by uid=0.
1457
Mimi Zohard68a6fe2016-12-19 16:22:57 -08001458 ima_canonical_fmt [IMA]
1459 Use the canonical format for the binary runtime
1460 measurements, instead of host native format.
1461
Mimi Zohar3323eec92009-02-04 09:06:58 -05001462 ima_hash= [IMA]
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001463 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1464 | sha512 | ... }
Mimi Zohar3323eec92009-02-04 09:06:58 -05001465 default: "sha1"
1466
Mimi Zohare7a2ad72013-06-07 12:16:37 +02001467 The list of supported hash algorithms is defined
1468 in crypto/hash_info.h.
1469
Mimi Zohar24fd03c2015-06-11 20:48:33 -04001470 ima_policy= [IMA]
1471 The builtin measurement policy to load during IMA
1472 setup. Specyfing "tcb" as the value, measures all
1473 programs exec'd, files mmap'd for exec, and all files
1474 opened with the read mode bit set by either the
1475 effective uid (euid=0) or uid=0.
1476 Format: "tcb"
1477
1478 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
Eric Paris5789ba32009-05-21 15:47:06 -04001479 Load a policy which meets the needs of the Trusted
1480 Computing Base. This means IMA will measure all
1481 programs exec'd, files mmap'd for exec, and all files
1482 opened for read by uid=0.
1483
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001484 ima_template= [IMA]
1485 Select one of defined IMA measurements template formats.
Roberto Sassu8265a2f2015-04-11 17:07:03 +02001486 Formats: { "ima" | "ima-ng" | "ima-sig" }
Roberto Sassu9b9d4ce2013-06-07 12:16:35 +02001487 Default: "ima-ng"
1488
Roberto Sassuc2426d22014-10-13 14:08:42 +02001489 ima_template_fmt=
1490 [IMA] Define a custom template format.
1491 Format: { "field1|...|fieldN" }
1492
Dmitry Kasatkin3bcced32014-02-26 17:05:20 +02001493 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1494 Format: <min_file_size>
1495 Set the minimal file size for using asynchronous hash.
1496 If left unspecified, ahash usage is disabled.
1497
1498 ahash performance varies for different data sizes on
1499 different crypto accelerators. This option can be used
1500 to achieve the best performance for a particular HW.
1501
Dmitry Kasatkin6edf7a82014-05-06 14:47:13 +03001502 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1503 Format: <bufsize>
1504 Set hashing buffer size. Default: 4k.
1505
1506 ahash performance varies for different chunk sizes on
1507 different crypto accelerators. This option can be used
1508 to achieve best performance for particular HW.
1509
Linus Torvalds1da177e2005-04-16 15:20:36 -07001510 init= [KNL]
1511 Format: <full_path>
1512 Run specified binary instead of /sbin/init as init
1513 process.
1514
1515 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1516 for working out where the kernel is dying during
1517 startup.
1518
Prarit Bhargava7b0b73d2014-06-04 16:12:17 -07001519 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1520 initcall functions. Useful for debugging built-in
1521 modules and initcalls.
1522
Linus Torvalds1da177e2005-04-16 15:20:36 -07001523 initrd= [BOOT] Specify the location of the initial ramdisk
1524
Dave Hansenacd547b2016-07-29 09:30:21 -07001525 init_pkru= [x86] Specify the default memory protection keys rights
1526 register contents for all processes. 0x55555554 by
1527 default (disallow access to all but pkey 0). Can
1528 override in debugfs after boot.
1529
Linus Torvalds1da177e2005-04-16 15:20:36 -07001530 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1531 Format: <irq>
1532
Fenghua Yu6bb2ff82013-05-21 15:35:17 -04001533 int_pln_enable [x86] Enable power limit notification interrupt
1534
Mimi Zohard726d8d2013-03-18 14:48:02 -04001535 integrity_audit=[IMA]
1536 Format: { "0" | "1" }
1537 0 -- basic integrity auditing messages. (Default)
1538 1 -- additional integrity auditing messages.
1539
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001540 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
Kyle McMartin0cd5c3c2009-02-04 14:29:19 -08001541 on
1542 Enable intel iommu driver.
Keshavamurthy, Anil Sba395922007-10-21 16:41:49 -07001543 off
1544 Disable intel iommu driver.
1545 igfx_off [Default Off]
1546 By default, gfx is mapped as normal device. If a gfx
1547 device has a dedicated DMAR unit, the DMAR unit is
1548 bypassed by not enabling DMAR with this option. In
1549 this case, gfx device will use physical address for
1550 DMA.
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001551 forcedac [x86_64]
1552 With this option iommu will not optimize to look
Randy Dunlap16290242011-08-13 12:34:52 -07001553 for io virtual address below 32-bit forcing dual
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001554 address cycle on pci bus for cards supporting greater
Randy Dunlap16290242011-08-13 12:34:52 -07001555 than 32-bit addressing. The default is to look
1556 for translation below 32-bit and if not available
Keshavamurthy, Anil S7d3b03c2007-10-21 16:41:53 -07001557 then look in the higher range.
mark gross5e0d2a62008-03-04 15:22:08 -08001558 strict [Default Off]
1559 With this option on every unmap_single operation will
1560 result in a hardware IOTLB flush operation as opposed
1561 to batching them for performance.
Youquan Song6dd9a7c2011-05-25 19:13:49 +01001562 sp_off [Default Off]
1563 By default, super page will be supported if Intel IOMMU
1564 has the capability. With this option, super page will
1565 not be supported.
David Woodhousec83b2f22015-06-12 10:15:49 +01001566 ecs_off [Default Off]
1567 By default, extended context tables will be supported if
1568 the hardware advertises that it has support both for the
1569 extended tables themselves, and also PASID support. With
1570 this option set, extended tables will not be used even
1571 on hardware which claims to support them.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001572
1573 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1574 0 disables intel_idle and fall back on acpi_idle.
baolex.ni22c6bbe2016-07-11 09:57:37 +08001575 1 to 9 specify maximum depth of C-state.
Masanari Iida2e92c7a2011-12-15 01:18:52 +09001576
Dirk Brandewie6be26492013-02-15 22:55:10 +01001577 intel_pstate= [X86]
1578 disable
1579 Do not enable intel_pstate as the default
1580 scaling driver for the supported processors
Rafael J. Wysocki001c76f2016-11-17 23:34:17 +01001581 passive
1582 Use intel_pstate as a scaling driver, but configure it
1583 to work with generic cpufreq governors (instead of
1584 enabling its internal governor). This mode cannot be
1585 used along with the hardware-managed P-states (HWP)
1586 feature.
Ethan Zhaoaa4ea342014-12-09 10:43:19 +09001587 force
1588 Enable intel_pstate on systems that prohibit it by default
1589 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1590 instead of acpi-cpufreq may disable platform features, such
1591 as thermal controls and power capping, that rely on ACPI
1592 P-States information being indicated to OSPM and therefore
1593 should be used with caution. This option does not work with
1594 processors that aren't supported by the intel_pstate driver
1595 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
Dirk Brandewie2f86dc42014-11-06 09:40:47 -08001596 no_hwp
1597 Do not enable hardware P state control (HWP)
1598 if available.
Kristen Carlson Accardid64c3b02015-02-06 13:41:55 -08001599 hwp_only
1600 Only load intel_pstate on systems which support
1601 hardware P state control (HWP) if available.
Srinivas Pandruvada9522a2f2016-04-27 15:48:06 -07001602 support_acpi_ppc
Srinivas Pandruvada2b3ec762016-04-27 15:48:08 -07001603 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1604 Description Table, specifies preferred power management
1605 profile as "Enterprise Server" or "Performance Server",
1606 then this feature is turned on by default.
Srinivas Pandruvada22449c02016-10-25 13:20:43 -07001607 per_cpu_perf_limits
1608 Allow per-logical-CPU P-State performance control limits using
1609 cpufreq sysfs interface
Dirk Brandewie6be26492013-02-15 22:55:10 +01001610
Chris Wrightd1423d52010-07-20 11:06:49 -07001611 intremap= [X86-64, Intel-IOMMU]
Chris Wrightd1423d52010-07-20 11:06:49 -07001612 on enable Interrupt Remapping (default)
1613 off disable Interrupt Remapping
1614 nosid disable Source ID checking
Suresh Siddha41750d32011-08-23 17:05:18 -07001615 no_x2apic_optout
1616 BIOS x2APIC opt-out request will be ignored
Feng Wub7d20632015-09-18 22:29:56 +08001617 nopost disable Interrupt Posting
Chris Wrightd1423d52010-07-20 11:06:49 -07001618
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001619 iomem= Disable strict checking of access to MMIO memory
1620 strict regions from userspace.
1621 relaxed
1622
1623 iommu= [x86]
1624 off
1625 force
1626 noforce
1627 biomerge
1628 panic
1629 nopanic
1630 merge
1631 nomerge
1632 forcesac
1633 soft
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001634 pt [x86, IA-64]
Thadeu Lima de Souza Cascardo4e287842014-10-23 19:19:35 -02001635 nobypass [PPC/POWERNV]
1636 Disable IOMMU bypass, using IOMMU for PCI devices.
Alex Williamsonbcb71ab2011-10-21 15:56:24 -04001637
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001638
1639 io7= [HW] IO7 for Marvel based alpha systems
1640 See comment before marvel_specify_io7 in
1641 arch/alpha/kernel/core_marvel.c.
1642
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301643 io_delay= [X86] I/O delay method
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001644 0x80
1645 Standard port 0x80 based delay
1646 0xed
1647 Alternate port 0xed based delay (needed on some systems)
Rene Hermanb02aae92008-01-30 13:30:05 +01001648 udelay
Ingo Molnar6e7c4022008-01-30 13:30:05 +01001649 Simple two microseconds delay
1650 none
1651 No delay
Rene Hermanb02aae92008-01-30 13:30:05 +01001652
Linus Torvalds1da177e2005-04-16 15:20:36 -07001653 ip= [IP_PNP]
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04001654 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001656 irqaffinity= [SMP] Set the default irq affinity mask
Noam Camus2d13e6c2016-10-11 13:51:35 -07001657 The argument is a cpu list, as described above.
Thomas Gleixnerfbf19802016-02-03 19:52:23 +01001658
Alan Cox200803d2005-06-28 20:45:18 -07001659 irqfixup [HW]
1660 When an interrupt is not handled search all handlers
1661 for it. Intended to get systems with badly broken
1662 firmware running.
1663
1664 irqpoll [HW]
1665 When an interrupt is not handled search all handlers
1666 for it. Also check all handlers each timer
1667 interrupt. Intended to get systems with badly broken
1668 firmware running.
1669
Linus Torvalds1da177e2005-04-16 15:20:36 -07001670 isapnp= [ISAPNP]
Randy Dunlapa9913042005-10-23 12:57:11 -07001671 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001672
1673 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
Noam Camus2d13e6c2016-10-11 13:51:35 -07001674 The argument is a cpu list, as described above.
Li Zefanb225d442008-11-06 12:53:39 -08001675
Linus Torvalds1da177e2005-04-16 15:20:36 -07001676 This option can be used to specify one or more CPUs
1677 to isolate from the general SMP balancing and scheduling
Li Zefanb225d442008-11-06 12:53:39 -08001678 algorithms. You can move a process onto or off an
1679 "isolated" CPU via the CPU affinity syscalls or cpuset.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001680 <cpu number> begins at 0 and the maximum value is
1681 "number of CPUs in system - 1".
1682
1683 This option is the preferred way to isolate CPUs. The
Randy Dunlapa9913042005-10-23 12:57:11 -07001684 alternative -- manually setting the CPU mask of all
1685 tasks in the system -- can cause problems and
1686 suboptimal load balancer performance.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001687
Randy Dunlapa9913042005-10-23 12:57:11 -07001688 iucv= [HW,NET]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001689
Joerg Roedel7d8bfa22013-04-09 21:27:19 +02001690 ivrs_ioapic [HW,X86_64]
1691 Provide an override to the IOAPIC-ID<->DEVICE-ID
1692 mapping provided in the IVRS ACPI table. For
1693 example, to map IOAPIC-ID decimal 10 to
1694 PCI device 00:14.0 write the parameter as:
1695 ivrs_ioapic[10]=00:14.0
1696
1697 ivrs_hpet [HW,X86_64]
1698 Provide an override to the HPET-ID<->DEVICE-ID
1699 mapping provided in the IVRS ACPI table. For
1700 example, to map HPET-ID decimal 0 to
1701 PCI device 00:14.0 write the parameter as:
1702 ivrs_hpet[0]=00:14.0
1703
Suravee Suthikulpanitca3bf5d2016-04-01 09:06:01 -04001704 ivrs_acpihid [HW,X86_64]
1705 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1706 mapping provided in the IVRS ACPI table. For
1707 example, to map UART-HID:UID AMD0020:0 to
1708 PCI device 00:14.5 write the parameter as:
1709 ivrs_acpihid[00:14.5]=AMD0020:0
1710
Linus Torvalds1da177e2005-04-16 15:20:36 -07001711 js= [HW,JOY] Analog joystick
1712 See Documentation/input/joystick.txt.
1713
Kees Cook65fe9352016-06-13 15:10:02 -07001714 nokaslr [KNL]
1715 When CONFIG_RANDOMIZE_BASE is set, this disables
1716 kernel and module base offset ASLR (Address Space
1717 Layout Randomization).
Kees Cook24f2e022014-06-13 13:30:36 -07001718
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07001719 keepinitrd [HW,ARM]
1720
Taku Izumi342332e2016-03-15 14:55:22 -07001721 kernelcore= [KNL,X86,IA-64,PPC]
1722 Format: nn[KMGTPE] | "mirror"
1723 This parameter
Mel Gormaned7ed362007-07-17 04:03:14 -07001724 specifies the amount of memory usable by the kernel
1725 for non-movable allocations. The requested amount is
1726 spread evenly throughout all nodes in the system. The
1727 remaining memory in each node is used for Movable
1728 pages. In the event, a node is too small to have both
1729 kernelcore and Movable pages, kernelcore pages will
1730 take priority and other nodes will have a larger number
Weiping Pan675217f2013-09-30 13:45:10 -07001731 of Movable pages. The Movable zone is used for the
Mel Gormaned7ed362007-07-17 04:03:14 -07001732 allocation of pages that may be reclaimed or moved
1733 by the page migration subsystem. This means that
1734 HugeTLB pages may not be allocated from this zone.
1735 Note that allocations like PTEs-from-HighMem still
1736 use the HighMem zone if it exists, and the Normal
1737 zone if it does not.
1738
Taku Izumi342332e2016-03-15 14:55:22 -07001739 Instead of specifying the amount of memory (nn[KMGTPE]),
1740 you can specify "mirror" option. In case "mirror"
1741 option is specified, mirrored (reliable) memory is used
1742 for non-movable allocations and remaining memory is used
1743 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1744 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1745 time.
1746
Jason Wessel4fe1da42010-05-20 21:04:31 -05001747 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1748 Format: <Controller#>[,poll interval]
1749 The controller # is the number of the ehci usb debug
1750 port as it is probed via PCI. The poll interval is
1751 optional and is the number seconds in between
1752 each poll cycle to the debug port in case you need
1753 the functionality for interrupting the kernel with
1754 gdb or control-c on the dbgp connection. When
1755 not using this parameter you use sysrq-g to break into
1756 the kernel debugger.
1757
Jason Wessel84c08fd2010-05-20 21:04:24 -05001758 kgdboc= [KGDB,HW] kgdb over consoles.
Jason Wesselada64e42010-05-20 21:04:24 -05001759 Requires a tty driver that supports console polling,
1760 or a supported polling keyboard driver (non-usb).
Jason Wessel65b5ac12010-08-05 09:22:33 -05001761 Serial only format: <serial_device>[,baud]
1762 keyboard only format: kbd
1763 keyboard and serial format: kbd,<serial_device>[,baud]
1764 Optional Kernel mode setting:
1765 kms, kbd format: kms,kbd
1766 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
Jason Wessel6cdf6e02008-04-17 20:05:38 +02001767
Jason Wessel84c08fd2010-05-20 21:04:24 -05001768 kgdbwait [KGDB] Stop kernel execution and enter the
1769 kernel debugger at the earliest opportunity.
1770
Florian Fainelli9bed90c62008-08-23 18:54:37 +02001771 kmac= [MIPS] korina ethernet MAC address.
1772 Configure the RouterBoard 532 series on-chip
1773 Ethernet adapter MAC address.
1774
Catalin Marinas04f70332009-06-11 13:22:39 +01001775 kmemleak= [KNL] Boot-time kmemleak enable/disable
1776 Valid arguments: on, off
1777 Default: on
Masanari Iida47aeedd2014-10-24 21:24:59 +09001778 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1779 the default is off.
Catalin Marinas04f70332009-06-11 13:22:39 +01001780
Xishi Qiuc3ac14b2014-01-23 15:53:33 -08001781 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1782 Valid arguments: 0, 1, 2
1783 kmemcheck=0 (disabled)
1784 kmemcheck=1 (enabled)
1785 kmemcheck=2 (one-shot mode)
1786 Default: 2 (one-shot mode)
1787
Andre Przywarafef07aa2009-07-10 14:20:35 +02001788 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1789 Default is 0 (don't ignore, but inject #GP)
1790
Xiao Guangronga182d872010-09-20 22:17:48 +08001791 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1792 KVM MMU at runtime.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001793 Default is 0 (off)
1794
Andre Przywarafef07aa2009-07-10 14:20:35 +02001795 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
Xiao Guangrong8475f942010-09-20 22:16:45 +08001796 Default is 1 (enabled)
Andre Przywarafef07aa2009-07-10 14:20:35 +02001797
1798 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1799 for all guests.
Randy Dunlap16290242011-08-13 12:34:52 -07001800 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
Andre Przywarafef07aa2009-07-10 14:20:35 +02001801
Andre Przywarafef07aa2009-07-10 14:20:35 +02001802 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1803 (virtualized MMU) support on capable Intel chips.
1804 Default is 1 (enabled)
1805
1806 kvm-intel.emulate_invalid_guest_state=
1807 [KVM,Intel] Enable emulation of invalid guest states
1808 Default is 0 (disabled)
1809
1810 kvm-intel.flexpriority=
1811 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1812 Default is 1 (enabled)
1813
Sasha Levine1a72ae2011-08-09 14:28:35 +03001814 kvm-intel.nested=
1815 [KVM,Intel] Enable VMX nesting (nVMX).
1816 Default is 0 (disabled)
1817
Andre Przywarafef07aa2009-07-10 14:20:35 +02001818 kvm-intel.unrestricted_guest=
1819 [KVM,Intel] Disable unrestricted guest feature
1820 (virtualized real and unpaged mode) on capable
1821 Intel chips. Default is 1 (enabled)
1822
1823 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1824 feature (tagged TLBs) on capable Intel chips.
1825 Default is 1 (enabled)
1826
Linus Torvalds1da177e2005-04-16 15:20:36 -07001827 l2cr= [PPC]
1828
Robert Brosea78bfbf2008-03-29 07:20:23 +11001829 l3cr= [PPC]
1830
Alan Coxcd4f0ef2007-07-31 00:37:59 -07001831 lapic [X86-32,APIC] Enable the local APIC even if BIOS
Randy Dunlapa9913042005-10-23 12:57:11 -07001832 disabled it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001833
Suresh Siddha279f1462012-10-22 14:37:58 -07001834 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1835 value for LAPIC timer one-shot implementation. Default
1836 back to the programmable timer unit in the LAPIC.
1837
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05301838 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
Randy Dunlapada9cfd2008-12-19 10:57:32 -08001839 in C2 power state.
Thomas Gleixnere585bef2007-03-23 16:08:01 +01001840
FD Camifcb71f62008-01-06 19:08:56 +01001841 libata.dma= [LIBATA] DMA control
1842 libata.dma=0 Disable all PATA and SATA DMA
1843 libata.dma=1 PATA and SATA Disk DMA only
1844 libata.dma=2 ATAPI (CDROM) DMA only
Randy Dunlap16290242011-08-13 12:34:52 -07001845 libata.dma=4 Compact Flash DMA only
FD Camifcb71f62008-01-06 19:08:56 +01001846 Combinations also work, so libata.dma=3 enables DMA
1847 for disks and CDROMs, but not CFs.
Randy Dunlap16290242011-08-13 12:34:52 -07001848
Michael Prokop20308872009-08-06 00:14:10 +02001849 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1850 libata.ignore_hpa=0 keep BIOS limits (default)
1851 libata.ignore_hpa=1 ignore limits, using full disk
FD Camifcb71f62008-01-06 19:08:56 +01001852
Dave Jones78e70c22007-09-27 11:50:13 -04001853 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1854 when set.
1855 Format: <int>
1856
Tejun Heo33267322008-02-13 09:15:09 +09001857 libata.force= [LIBATA] Force configurations. The format is comma
1858 separated list of "[ID:]VAL" where ID is
Roman Fietze4c44f302010-04-21 12:17:12 +02001859 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
Tejun Heo33267322008-02-13 09:15:09 +09001860 matching port, link or device. Basically, it matches
1861 the ATA ID string printed on console by libata. If
1862 the whole ID part is omitted, the last PORT and DEVICE
1863 values are used. If ID hasn't been specified yet, the
1864 configuration applies to all ports, links and devices.
1865
1866 If only DEVICE is omitted, the parameter applies to
1867 the port and all links and devices behind it. DEVICE
1868 number of 0 either selects the first device or the
1869 first fan-out link behind PMP device. It does not
1870 select the host link. DEVICE number of 15 selects the
1871 host link and device attached to it.
1872
1873 The VAL specifies the configuration to force. As long
1874 as there's no ambiguity shortcut notation is allowed.
1875 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1876 The following configurations can be forced.
1877
1878 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1879 Any ID with matching PORT is used.
1880
1881 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1882
1883 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1884 udma[/][16,25,33,44,66,100,133] notation is also
1885 allowed.
1886
1887 * [no]ncq: Turn on or off NCQ.
1888
Martin K. Petersend7b16e42015-05-04 21:54:18 -04001889 * [no]ncqtrim: Turn off queued DSM TRIM.
1890
Tejun Heo05944bd2008-08-13 20:19:09 +09001891 * nohrst, nosrst, norst: suppress hard, soft
1892 and both resets.
1893
Dan Williamsca6d43b2012-06-21 23:41:41 -07001894 * rstonce: only attempt one reset during
1895 hot-unplug link recovery
1896
Tejun Heo43c9c592010-05-23 12:59:11 +02001897 * dump_id: dump IDENTIFY data.
1898
Vincent Pelletier966fbe12013-05-21 22:30:58 +02001899 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1900
Robin H. Johnsonb8bd6dc2013-12-16 09:31:19 -08001901 * disable: Disable this device.
1902
Tejun Heo33267322008-02-13 09:15:09 +09001903 If there are multiple matching configurations changing
1904 the same attribute, the last one is used.
1905
Yinghai Lu95f72d12010-07-12 14:36:09 +10001906 memblock=debug [KNL] Enable memblock debug messages.
Randy Dunlap7c4be2532009-01-06 14:42:44 -08001907
Linus Torvalds1da177e2005-04-16 15:20:36 -07001908 load_ramdisk= [RAM] List of ramdisks to load from floppy
Randy Dunlap31c00fc2008-11-13 21:33:24 +00001909 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001910
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001911 lockd.nlm_grace_period=P [NFS] Assign grace period.
1912 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001913
Randy Dunlapa6b25b62006-01-14 13:21:19 -08001914 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1915 Format: <integer>
1916
1917 lockd.nlm_timeout=T [NFS] Assign timeout value.
1918 Format: <integer>
1919
1920 lockd.nlm_udpport=M [NFS] Assign UDP port.
1921 Format: <integer>
Linus Torvalds1da177e2005-04-16 15:20:36 -07001922
Paul E. McKenneyec4518a2014-09-12 10:50:01 -07001923 locktorture.nreaders_stress= [KNL]
1924 Set the number of locking read-acquisition kthreads.
1925 Defaults to being automatically set based on the
1926 number of online CPUs.
1927
1928 locktorture.nwriters_stress= [KNL]
1929 Set the number of locking write-acquisition kthreads.
1930
1931 locktorture.onoff_holdoff= [KNL]
1932 Set time (s) after boot for CPU-hotplug testing.
1933
1934 locktorture.onoff_interval= [KNL]
1935 Set time (s) between CPU-hotplug operations, or
1936 zero to disable CPU-hotplug testing.
1937
1938 locktorture.shuffle_interval= [KNL]
1939 Set task-shuffle interval (jiffies). Shuffling
1940 tasks allows some CPUs to go into dyntick-idle
1941 mode during the locktorture test.
1942
1943 locktorture.shutdown_secs= [KNL]
1944 Set time (s) after boot system shutdown. This
1945 is useful for hands-off automated testing.
1946
1947 locktorture.stat_interval= [KNL]
1948 Time (s) between statistics printk()s.
1949
1950 locktorture.stutter= [KNL]
1951 Time (s) to stutter testing, for example,
1952 specifying five seconds causes the test to run for
1953 five seconds, wait for five seconds, and so on.
1954 This tests the locking primitive's ability to
1955 transition abruptly to and from idle.
1956
1957 locktorture.torture_runnable= [BOOT]
1958 Start locktorture running at boot time.
1959
1960 locktorture.torture_type= [KNL]
1961 Specify the locking implementation to test.
1962
1963 locktorture.verbose= [KNL]
1964 Enable additional printk() statements.
1965
Linus Torvalds1da177e2005-04-16 15:20:36 -07001966 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1967 Format: <irq>
1968
1969 loglevel= All Kernel Messages with a loglevel smaller than the
1970 console loglevel will be printed to the console. It can
1971 also be changed with klogd or other programs. The
1972 loglevels are defined as follows:
1973
1974 0 (KERN_EMERG) system is unusable
1975 1 (KERN_ALERT) action must be taken immediately
1976 2 (KERN_CRIT) critical conditions
1977 3 (KERN_ERR) error conditions
1978 4 (KERN_WARNING) warning conditions
1979 5 (KERN_NOTICE) normal but significant condition
1980 6 (KERN_INFO) informational
1981 7 (KERN_DEBUG) debug-level messages
1982
Randy Dunlapc756d082011-02-20 20:08:35 -08001983 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
Luis R. Rodriguez23b28992014-08-06 16:08:56 -07001984 in bytes. n must be a power of two and greater
1985 than the minimal size. The minimal size is defined
1986 by LOG_BUF_SHIFT kernel config parameter. There is
1987 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1988 that allows to increase the default size depending on
1989 the number of CPUs. See init/Kconfig for more details.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001990
Randy Dunlapaccaa242007-10-16 01:29:37 -07001991 logo.nologo [FB] Disables display of the built-in Linux logo.
1992 This may be used to provide more screen space for
1993 kernel log messages and is useful when debugging
1994 kernel boot problems.
1995
Linus Torvalds1da177e2005-04-16 15:20:36 -07001996 lp=0 [LP] Specify parallel ports to use, e.g,
1997 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1998 lp=reset first parallel port). 'lp=0' disables the
1999 lp=auto printer driver. 'lp=reset' (which can be
2000 specified in addition to the ports) causes
2001 attached printers to be reset. Using
2002 lp=port1,port2,... specifies the parallel ports
2003 to associate lp devices with, starting with
2004 lp0. A port specification may be 'none' to skip
2005 that lp device, or a parport name such as
2006 'parport0'. Specifying 'lp=auto' instead of a
2007 port specification list means that device IDs
2008 from each port should be examined, to see if
2009 an IEEE 1284-compliant printer is attached; if
2010 so, the driver will manage that printer.
2011 See also header of drivers/char/lp.c.
2012
2013 lpj=n [KNL]
2014 Sets loops_per_jiffy to given constant, thus avoiding
2015 time-consuming boot-time autodetection (up to 250 ms per
2016 CPU). 0 enables autodetection (default). To determine
2017 the correct value for your kernel, boot with normal
2018 autodetection and see what value is printed. Note that
2019 on SMP systems the preset will be applied to all CPUs,
2020 which is likely to cause problems if your CPUs need
2021 significantly divergent settings. An incorrect value
2022 will cause delays in the kernel to be wrong, leading to
2023 unpredictable I/O errors and other breakage. Although
2024 unlikely, in the extreme case this might damage your
2025 hardware.
2026
2027 ltpc= [NET]
2028 Format: <io>,<irq>,<dma>
2029
Randy Dunlap16290242011-08-13 12:34:52 -07002030 machvec= [IA-64] Force the use of a particular machine-vector
Randy Dunlapa9913042005-10-23 12:57:11 -07002031 (machvec) in a generic kernel.
2032 Example: machvec=hpzx1_swiotlb
Linus Torvalds1da177e2005-04-16 15:20:36 -07002033
Wu Zhangjin3209e702009-07-02 23:27:12 +08002034 machtype= [Loongson] Share the same kernel image file between different
2035 yeeloong laptop.
2036 Example: machtype=lemote-yeeloong-2f-7inch
2037
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002038 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2039 than or equal to this physical address is ignored.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002040
2041 maxcpus= [SMP] Maximum number of processors that an SMP kernel
Baoquan He7c142bf2016-08-24 13:06:45 +08002042 will bring up during bootup. maxcpus=n : n >= 0 limits
2043 the kernel to bring up 'n' processors. Surely after
2044 bootup you can bring up the other plugged cpu by executing
2045 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2046 only takes effect during system bootup.
2047 While n=0 is a special case, it is equivalent to "nosmp",
2048 which also disables the IO APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002049
Kay Sieversd134b002011-07-31 22:08:04 +02002050 max_loop= [LOOP] The number of loop block devices that get
2051 (loop.max_loop) unconditionally pre-created at init time. The default
2052 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2053 of statically allocating a predefined number, loop
2054 devices can be requested on-demand with the
2055 /dev/loop-control interface.
Bob Picco2b2c3752005-06-29 18:00:00 -07002056
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002057 mce [X86-32] Machine Check Exception
Linus Torvalds1da177e2005-04-16 15:20:36 -07002058
Uwe Hermann71cced62008-10-20 09:32:21 -07002059 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
Andi Kleen909dd322007-10-17 18:04:38 +02002060
Linus Torvalds1da177e2005-04-16 15:20:36 -07002061 md= [HW] RAID subsystems devices and level
Jani Nikulae52347b2016-11-03 12:10:10 +02002062 See Documentation/admin-guide/md.rst.
Randy Dunlapa9913042005-10-23 12:57:11 -07002063
Linus Torvalds1da177e2005-04-16 15:20:36 -07002064 mdacon= [MDA]
2065 Format: <first>,<last>
2066 Specifies range of consoles to be captured by the MDA.
Randy Dunlapa9913042005-10-23 12:57:11 -07002067
Linus Torvalds1da177e2005-04-16 15:20:36 -07002068 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2069 Amount of memory to be used when the kernel is not able
2070 to see the whole system memory or for test.
Wen Congyangfbb97d82012-12-17 15:59:29 -08002071 [X86] Work as limiting max address. Use together
2072 with memmap= to avoid physical address space collisions.
2073 Without memmap= PCI devices could be placed at addresses
2074 belonging to unused RAM.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002075
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002076 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -07002077 memory.
2078
Paul Mundt6902aa82008-09-21 17:14:42 +09002079 memchunk=nn[KMG]
2080 [KNL,SH] Allow user to override the default size for
2081 per-device physically contiguous DMA buffers.
2082
Vitaly Kuznetsov86dd9952016-05-19 17:13:06 -07002083 memhp_default_state=online/offline
2084 [KNL] Set the initial state for the memory hotplug
2085 onlining policy. If not specified, the default value is
2086 set according to the
2087 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2088 option.
2089 See Documentation/memory-hotplug.txt.
2090
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302091 memmap=exactmap [KNL,X86] Enable setting of an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07002092 E820 memory map, as specified by the user.
2093 Such memmap=exactmap lines can be constructed based on
2094 BIOS output or other requirements. See the memmap=nn@ss
2095 option description.
2096
2097 memmap=nn[KMG]@ss[KMG]
Randy Dunlap277cba12014-02-06 12:04:19 -08002098 [KNL] Force usage of a specific region of memory.
2099 Region of memory to be used is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002100
2101 memmap=nn[KMG]#ss[KMG]
2102 [KNL,ACPI] Mark specific memory as ACPI data.
Randy Dunlap277cba12014-02-06 12:04:19 -08002103 Region of memory to be marked is from ss to ss+nn.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002104
2105 memmap=nn[KMG]$ss[KMG]
2106 [KNL,ACPI] Mark specific memory as reserved.
Randy Dunlap277cba12014-02-06 12:04:19 -08002107 Region of memory to be reserved is from ss to ss+nn.
Pavel Machek13128482008-03-24 12:29:43 -07002108 Example: Exclude memory from 0x18690000-0x1869ffff
2109 memmap=64K$0x18690000
2110 or
2111 memmap=0x10000$0x18690000
Linus Torvalds1da177e2005-04-16 15:20:36 -07002112
Christoph Hellwigec776ef2015-04-01 09:12:18 +02002113 memmap=nn[KMG]!ss[KMG]
2114 [KNL,X86] Mark specific memory as protected.
2115 Region of memory to be used, from ss to ss+nn.
2116 The memory region may be marked as e820 type 12 (0xc)
2117 and is NVDIMM or ADR memory.
2118
Jeremy Fitzhardinge9f077872008-09-07 01:51:34 -07002119 memory_corruption_check=0/1 [X86]
2120 Some BIOSes seem to corrupt the first 64k of
2121 memory when doing things like suspend/resume.
2122 Setting this option will scan the memory
2123 looking for corruption. Enabling this will
2124 both detect corruption and prevent the kernel
2125 from using the memory being corrupted.
2126 However, its intended as a diagnostic tool; if
2127 repeatable BIOS-originated corruption always
2128 affects the same memory, you can use memmap=
2129 to prevent the kernel from using that memory.
2130
2131 memory_corruption_check_size=size [X86]
2132 By default it checks for corruption in the low
2133 64k, making this memory unavailable for normal
2134 use. Use this parameter to scan for
2135 corruption in more or less memory.
2136
2137 memory_corruption_check_period=seconds [X86]
2138 By default it checks for corruption every 60
2139 seconds. Use this parameter to check at some
2140 other rate. 0 disables periodic checking.
2141
Vladimir Murzine4b0db72015-04-14 15:48:43 -07002142 memtest= [KNL,X86,ARM] Enable memtest
Yinghai Luc64df702008-03-21 18:56:19 -07002143 Format: <integer>
Yinghai Luc64df702008-03-21 18:56:19 -07002144 default : 0 <disable>
Andreas Herrmann9e5f6cf2009-02-25 11:30:45 +01002145 Specifies the number of memtest passes to be
2146 performed. Each pass selects another test
2147 pattern from a given set of patterns. Memtest
2148 fills the memory with this pattern, validates
2149 memory contents and reserves bad memory
2150 regions that are detected.
Yinghai Luc64df702008-03-21 18:56:19 -07002151
Rafael J. Wysocki406e7932016-11-21 22:45:40 +01002152 mem_sleep_default= [SUSPEND] Default system suspend mode:
2153 s2idle - Suspend-To-Idle
2154 shallow - Power-On Suspend or equivalent (if supported)
2155 deep - Suspend-To-RAM or equivalent (if supported)
2156 See Documentation/power/states.txt.
2157
Linus Torvalds1da177e2005-04-16 15:20:36 -07002158 meye.*= [HW] Set MotionEye Camera parameters
2159 See Documentation/video4linux/meye.txt.
2160
Andres Salomon8f368812007-10-12 23:04:06 +02002161 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2162 Multi-Function General Purpose Timers on AMD Geode
2163 platforms.
2164
Willy Tarreaue6c4dc62008-01-30 13:33:33 +01002165 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2166 the BIOS has incorrectly applied a workaround. TinyBIOS
2167 version 0.98 is known to be affected, 0.99 fixes the
2168 problem by letting the user disable the workaround.
2169
Linus Torvalds1da177e2005-04-16 15:20:36 -07002170 mga= [HW,DRM]
2171
Randy Dunlap1c207f92008-11-19 15:36:16 -08002172 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2173 physical address is ignored.
2174
Michel Pollet39f45d72009-05-20 11:10:31 +01002175 mini2440= [ARM,HW,KNL]
2176 Format:[0..2][b][c][t]
2177 Default: "0tb"
2178 MINI2440 configuration specification:
2179 0 - The attached screen is the 3.5" TFT
2180 1 - The attached screen is the 7" TFT
2181 2 - The VGA Shield is attached (1024x768)
2182 Leaving out the screen size parameter will not load
2183 the TFT driver, and the framebuffer will be left
2184 unconfigured.
2185 b - Enable backlight. The TFT backlight pin will be
2186 linked to the kernel VESA blanking code and a GPIO
2187 LED. This parameter is not necessary when using the
2188 VGA shield.
2189 c - Enable the s3c camera interface.
2190 t - Reserved for enabling touchscreen support. The
2191 touchscreen support is not enabled in the mainstream
2192 kernel as of 2.6.30, a preliminary port can be found
2193 in the "bleeding edge" mini2440 support kernel at
2194 http://repo.or.cz/w/linux-2.6/mini2440.git
2195
Mel Gorman6b74ab92008-07-23 21:26:49 -07002196 mminit_loglevel=
2197 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2198 parameter allows control of the logging verbosity for
2199 the additional memory initialisation checks. A value
2200 of 0 disables mminit logging and a level of 4 will
2201 log everything. Information is printed at KERN_DEBUG
2202 so loglevel=8 may also need to be specified.
2203
Rusty Russell106a4ee2012-09-26 10:09:40 +01002204 module.sig_enforce
2205 [KNL] When CONFIG_MODULE_SIG is set, this means that
2206 modules without (valid) signatures will fail to load.
Paul Bolle2a039be2013-03-25 20:42:06 +01002207 Note that if CONFIG_MODULE_SIG_FORCE is set, that
Rusty Russell106a4ee2012-09-26 10:09:40 +01002208 is always true, so this option does nothing.
2209
Prarit Bhargavabe7de5f2016-07-21 15:37:56 +09302210 module_blacklist= [KNL] Do not load a comma-separated list of
2211 modules. Useful for debugging problem modules.
2212
Linus Torvalds1da177e2005-04-16 15:20:36 -07002213 mousedev.tap_time=
2214 [MOUSE] Maximum time between finger touching and
2215 leaving touchpad surface for touch to be considered
2216 a tap and be reported as a left button click (for
2217 touchpads working in absolute mode only).
2218 Format: <msecs>
2219 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2220 reporting absolute coordinates, such as tablets
2221 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2222 reporting absolute coordinates, such as tablets
2223
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302224 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002225 is similar to kernelcore except it specifies the
2226 amount of memory used for migratable allocations.
2227 If both kernelcore and movablecore is specified,
2228 then kernelcore will be at *least* the specified
2229 value but may be more. If movablecore on its own
2230 is specified, the administrator must be careful
2231 that the amount of memory usable for all allocations
2232 is not too small.
2233
Reza Arbab39fa1042016-12-12 16:42:55 -08002234 movable_node [KNL] Boot-time switch to enable the effects
Tang Chenc5320922013-11-12 15:08:10 -08002235 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2236
Linus Torvalds1da177e2005-04-16 15:20:36 -07002237 MTD_Partition= [MTD]
2238 Format: <name>,<region-number>,<size>,<offset>
2239
Randy Dunlapa9913042005-10-23 12:57:11 -07002240 MTD_Region= [MTD] Format:
2241 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
Linus Torvalds1da177e2005-04-16 15:20:36 -07002242
2243 mtdparts= [MTD]
Randy Dunlapc8facbb2007-07-31 00:37:40 -07002244 See drivers/mtd/cmdlinepart.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002245
Will Schmidt4e89a2d2010-09-28 15:33:12 +00002246 multitce=off [PPC] This parameter disables the use of the pSeries
2247 firmware feature for updating multiple TCE entries
2248 at a time.
2249
Rohit Hagargundgi5988af22009-05-12 13:46:57 -07002250 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2251
2252 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2253
2254 boundary - index of last SLC block on Flex-OneNAND.
2255 The remaining blocks are configured as MLC blocks.
2256 lock - Configure if Flex-OneNAND boundary should be locked.
2257 Once locked, the boundary cannot be changed.
2258 1 indicates lock status, 0 indicates unlock status.
2259
Ben Dooks9db829f2008-07-03 11:24:29 +01002260 mtdset= [ARM]
2261 ARM/S3C2412 JIVE boot control
2262
2263 See arch/arm/mach-s3c2412/mach-jive.c
2264
Linus Torvalds1da177e2005-04-16 15:20:36 -07002265 mtouchusb.raw_coordinates=
Randy Dunlapa9913042005-10-23 12:57:11 -07002266 [HW] Make the MicroTouch USB driver use raw coordinates
2267 ('y', default) or cooked coordinates ('n')
Linus Torvalds1da177e2005-04-16 15:20:36 -07002268
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002269 mtrr_chunk_size=nn[KMG] [X86]
Matt LaPlante19f59462009-04-27 15:06:31 +02002270 used for mtrr cleanup. It is largest continuous chunk
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002271 that could hold holes aka. UC entries.
2272
2273 mtrr_gran_size=nn[KMG] [X86]
2274 Used for mtrr cleanup. It is granularity of mtrr block.
2275 Default is 1.
2276 Large value could prevent small alignment from
2277 using up MTRRs.
2278
2279 mtrr_spare_reg_nr=n [X86]
2280 Format: <integer>
2281 Range: 0,7 : spare reg number
2282 Default : 1
2283 Used for mtrr cleanup. It is spare mtrr entries number.
2284 Set to 2 or more if your graphical card needs more.
2285
Linus Torvalds1da177e2005-04-16 15:20:36 -07002286 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2287
Linus Torvalds1da177e2005-04-16 15:20:36 -07002288 netdev= [NET] Network devices parameters
2289 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2290 Note that mem_start is often overloaded to mean
2291 something different and driver-specific.
Randy Dunlapa9913042005-10-23 12:57:11 -07002292 This usage is only documented in each driver source
2293 file if at all.
2294
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002295 nf_conntrack.acct=
2296 [NETFILTER] Enable connection tracking flow accounting
2297 0 to disable accounting
2298 1 to enable accounting
Tim Gardnerd70a0112010-06-25 14:46:56 +02002299 Default value is 0.
Krzysztof Piotr Oledzki58401572008-07-21 10:01:34 -07002300
Chuck Lever306a0752010-09-17 10:54:37 -04002301 nfsaddrs= [NFS] Deprecated. Use ip= instead.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002302 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002303
2304 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
J. Bruce Fieldsdc7a0812009-10-27 14:41:35 -04002305 See Documentation/filesystems/nfs/nfsroot.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002306
Chuck Lever306a0752010-09-17 10:54:37 -04002307 nfsrootdebug [NFS] enable nfsroot debugging messages.
2308 See Documentation/filesystems/nfs/nfsroot.txt.
2309
Trond Myklebust5405fc42016-08-29 20:03:52 -04002310 nfs.callback_nr_threads=
2311 [NFSv4] set the total number of threads that the
2312 NFS client will assign to service NFSv4 callback
2313 requests.
2314
Trond Myklebusta72b4422006-01-03 09:55:41 +01002315 nfs.callback_tcpport=
2316 [NFS] set the TCP port on which the NFSv4 callback
2317 channel should listen.
2318
Trond Myklebuste571cbf2009-08-19 18:12:27 -04002319 nfs.cache_getent=
2320 [NFS] sets the pathname to the program which is used
2321 to update the NFS client cache entries.
2322
2323 nfs.cache_getent_timeout=
2324 [NFS] sets the timeout after which an attempt to
2325 update a cache entry is deemed to have failed.
2326
Trond Myklebust58df0952006-01-03 09:55:57 +01002327 nfs.idmap_cache_timeout=
2328 [NFS] set the maximum lifetime for idmapper cache
2329 entries.
2330
Trond Myklebustf43bf0b2007-10-09 12:01:04 -04002331 nfs.enable_ino64=
2332 [NFS] enable 64-bit inode numbers.
2333 If zero, the NFS client will fake up a 32-bit inode
2334 number for the readdir() and stat() syscalls instead
2335 of returning the full 64-bit number.
2336 The default is to return 64-bit inode numbers.
2337
Trond Myklebust5405fc42016-08-29 20:03:52 -04002338 nfs.max_session_cb_slots=
2339 [NFSv4.1] Sets the maximum number of session
2340 slots the client will assign to the callback
2341 channel. This determines the maximum number of
2342 callbacks the client will process in parallel for
2343 a particular server.
2344
Trond Myklebustef159e92012-02-06 19:50:40 -05002345 nfs.max_session_slots=
2346 [NFSv4.1] Sets the maximum number of session slots
2347 the client will attempt to negotiate with the server.
2348 This limits the number of simultaneous RPC requests
2349 that the client can send to the NFSv4.1 server.
2350 Note that there is little point in setting this
2351 value higher than the max_tcp_slot_table_limit.
2352
Trond Myklebustb064eca22011-02-22 15:44:32 -08002353 nfs.nfs4_disable_idmapping=
Trond Myklebust074b1d12012-01-09 13:46:26 -05002354 [NFSv4] When set to the default of '1', this option
2355 ensures that both the RPC level authentication
2356 scheme and the NFS level operations agree to use
2357 numeric uids/gids if the mount is using the
2358 'sec=sys' security flavour. In effect it is
2359 disabling idmapping, which can make migration from
2360 legacy NFSv2/v3 systems to NFSv4 easier.
2361 Servers that do not support this mode of operation
2362 will be autodetected by the client, and it will fall
2363 back to using the idmapper.
2364 To turn off this behaviour, set the value to '0'.
Chuck Lever6f2ea7f2012-09-14 17:24:41 -04002365 nfs.nfs4_unique_id=
2366 [NFS4] Specify an additional fixed unique ident-
2367 ification string that NFSv4 clients can insert into
2368 their nfs_client_id4 string. This is typically a
2369 UUID that is generated at system install time.
Trond Myklebustb064eca22011-02-22 15:44:32 -08002370
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002371 nfs.send_implementation_id =
2372 [NFSv4.1] Send client implementation identification
2373 information in exchange_id requests.
2374 If zero, no implementation identification information
2375 will be sent.
2376 The default is to send the implementation identification
2377 information.
Jani Nikulae52347b2016-11-03 12:10:10 +02002378
Trond Myklebustf6de7a32013-09-04 10:08:54 -04002379 nfs.recover_lost_locks =
2380 [NFSv4] Attempt to recover locks that were lost due
2381 to a lease timeout on the server. Please note that
2382 doing this risks data corruption, since there are
2383 no guarantees that the file will remain unchanged
2384 after the locks are lost.
2385 If you want to enable the kernel legacy behaviour of
2386 attempting to recover these locks, then set this
2387 parameter to '1'.
2388 The default parameter value of '0' causes the kernel
2389 not to attempt recovery of lost locks.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002390
Trond Myklebustbbf58bf2015-08-24 20:39:18 -04002391 nfs4.layoutstats_timer =
2392 [NFSv4.2] Change the rate at which the kernel sends
2393 layoutstats to the pNFS metadata server.
2394
2395 Setting this to value to 0 causes the kernel to use
2396 whatever value is the default set by the layout
2397 driver. A non-zero value sets the minimum interval
2398 in seconds between layoutstats transmissions.
2399
J. Bruce Fieldse9541ce2012-03-22 16:07:18 -04002400 nfsd.nfs4_disable_idmapping=
2401 [NFSv4] When set to the default of '1', the NFSv4
2402 server will return only numeric uids and gids to
2403 clients using auth_sys, and will accept numeric uids
2404 and gids from such clients. This is intended to ease
2405 migration from NFSv2/v3.
Weston Andros Adamsondb8ac8b2012-02-17 15:20:24 -05002406
Sachin Bhamare18d98f62012-03-19 20:47:58 -07002407 objlayoutdriver.osd_login_prog=
2408 [NFS] [OBJLAYOUT] sets the pathname to the program which
2409 is used to automatically discover and login into new
2410 osd-targets. Please see:
2411 Documentation/filesystems/pnfs.txt for more explanations
2412
Paul Mundt1e1030d2009-09-01 17:38:32 +09002413 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
Haavard Skinnemoene7ba1762007-10-10 14:58:29 +02002414 when a NMI is triggered.
2415 Format: [state][,regs][,debounce][,die]
2416
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302417 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
Don Zickusfef2c9b2011-03-22 16:34:16 -07002418 Format: [panic,][nopanic,][num]
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002419 Valid num: 0 or 1
Pranith Kumar334bb792015-10-10 15:40:42 -04002420 0 - turn hardlockup detector in nmi_watchdog off
2421 1 - turn hardlockup detector in nmi_watchdog on
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002422 When panic is specified, panic when an NMI watchdog
Don Zickusfef2c9b2011-03-22 16:34:16 -07002423 timeout occurs (or 'nopanic' to override the opposite
Pranith Kumar334bb792015-10-10 15:40:42 -04002424 default). To disable both hard and soft lockup detectors,
2425 please see 'nowatchdog'.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002426 This is useful when you use a panic=... timeout and
2427 need the box quickly up again.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002428
Anton Vorontsovbff38772009-07-08 11:10:56 -07002429 netpoll.carrier_timeout=
2430 [NET] Specifies amount of time (in seconds) that
2431 netpoll should wait for a carrier. By default netpoll
2432 waits 4 seconds.
2433
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002434 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
Linus Torvalds1da177e2005-04-16 15:20:36 -07002435 emulation library even if a 387 maths coprocessor
2436 is present.
2437
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002438 no_console_suspend
2439 [HW] Never suspend the console
2440 Disable suspending of consoles during suspend and
2441 hibernate operations. Once disabled, debugging
2442 messages can reach various consoles while the rest
2443 of the system is being put to sleep (ie, while
2444 debugging driver suspend/resume hooks). This may
2445 not work reliably with all consoles, but is known
2446 to work with serial and VGA consoles.
Yanmin Zhang134620f2011-10-31 17:11:27 -07002447 To facilitate more flexible debugging, we also add
2448 console_suspend, a printk module parameter to control
2449 it. Users could use console_suspend (usually
2450 /sys/module/printk/parameters/console_suspend) to
2451 turn on/off it dynamically.
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002452
Christoph Lameterc1aee212007-05-31 00:40:47 -07002453 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2454 caches in the slab allocator. Saves per-node memory,
2455 but will impact performance.
Paul Menage3395ee02006-12-06 20:32:16 -08002456
Randy Dunlapa9913042005-10-23 12:57:11 -07002457 noalign [KNL,ARM]
2458
Linus Torvalds1da177e2005-04-16 15:20:36 -07002459 noapic [SMP,APIC] Tells the kernel to not make use of any
2460 IOAPICs that may be present in the system.
2461
Mike Galbraith5091faa2010-11-30 14:18:03 +01002462 noautogroup Disable scheduler automatic task group creation.
2463
Linus Torvalds1da177e2005-04-16 15:20:36 -07002464 nobats [PPC] Do not use BATs for mapping kernel lowmem
2465 on "Classic" PPC cores.
2466
2467 nocache [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002468
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002469 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2470
Shailabh Nagar163ecdf2006-07-30 03:03:11 -07002471 nodelayacct [KNL] Disable per-task delay accounting
2472
Paul Mundt6902aa82008-09-21 17:14:42 +09002473 nodsp [SH] Disable hardware DSP at boot time.
2474
Dave Youngb2e0a542014-08-14 17:15:26 +08002475 noefi Disable EFI runtime services support.
Huang, Ying8b2cb7a2008-01-30 13:32:11 +01002476
Linus Torvalds1da177e2005-04-16 15:20:36 -07002477 noexec [IA-64]
2478
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302479 noexec [X86]
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002480 On X86-32 available only on PAE configured kernels.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002481 noexec=on: enable non-executable mappings (default)
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002482 noexec=off: disable non-executable mappings
2483
H. Peter Anvin52b61792012-09-21 12:43:13 -07002484 nosmap [X86]
2485 Disable SMAP (Supervisor Mode Access Prevention)
2486 even if it is supported by processor.
2487
Fenghua Yude5397a2011-05-11 16:51:05 -07002488 nosmep [X86]
H. Peter Anvin52b61792012-09-21 12:43:13 -07002489 Disable SMEP (Supervisor Mode Execution Prevention)
Fenghua Yude5397a2011-05-11 16:51:05 -07002490 even if it is supported by processor.
2491
Jiri Slabyf5a1b192008-04-12 10:28:25 +02002492 noexec32 [X86-64]
2493 This affects only 32-bit executables.
2494 noexec32=on: enable non-executable mappings (default)
2495 read doesn't imply executable mappings
2496 noexec32=off: disable non-executable mappings
2497 read implies executable mappings
Linus Torvalds1da177e2005-04-16 15:20:36 -07002498
Maciej W. Rozyckifab43ef2015-04-03 23:23:34 +01002499 nofpu [MIPS,SH] Disable hardware FPU at boot time.
Paul Mundt6902aa82008-09-21 17:14:42 +09002500
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002501 nofxsr [BUGS=X86-32] Disables x86 floating point extended
Chuck Ebbert4f886512006-03-23 02:59:34 -08002502 register save and restore. The kernel will only save
2503 legacy floating-point registers on task switch.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002504
Toshi Kani0ddab1d2015-04-14 15:47:20 -07002505 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2506
Sascha Silbe52c48c52016-04-05 12:53:38 +02002507 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2508 Equivalent to smt=1.
2509
Suresh Siddha0c752a92009-05-22 12:17:45 -07002510 noxsave [BUGS=X86] Disables x86 extended register state save
2511 and restore using xsave. The kernel will fallback to
2512 enabling legacy floating-point and sse state.
2513
Fenghua Yub6f42a42014-05-29 11:12:31 -07002514 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2515 register states. The kernel will fall back to use
2516 xsave to save the states. By using this parameter,
2517 performance of saving the states is degraded because
2518 xsave doesn't support modified optimization while
2519 xsaveopt supports it on xsaveopt enabled systems.
2520
2521 noxsaves [X86] Disables xsaves and xrstors used in saving and
2522 restoring x86 extended register state in compacted
2523 form of xsave area. The kernel will fall back to use
2524 xsaveopt and xrstor to save and restore the states
2525 in standard form of xsave area. By using this
2526 parameter, xsave area per process might occupy more
2527 memory on xsaves enabled systems.
2528
Paulius Zaleckas01a24d22009-03-31 13:55:44 +01002529 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2530 wfi(ARM) instruction doesn't work correctly and not to
2531 use it. This is also useful when using JTAG debugger.
Randy Dunlapa9913042005-10-23 12:57:11 -07002532
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -06002533 no_file_caps Tells the kernel not to honor file capabilities. The
2534 only way then for a file to be executed with privilege
2535 is to be setuid root or executed by root.
2536
Linus Torvalds1da177e2005-04-16 15:20:36 -07002537 nohalt [IA-64] Tells the kernel not to use the power saving
2538 function PAL_HALT_LIGHT when idle. This increases
2539 power-consumption. On the positive side, it reduces
2540 interrupt wake-up latency, which may improve performance
2541 in certain environments such as networked servers or
2542 real-time systems.
2543
Kees Cooka6e15a32014-06-13 13:30:35 -07002544 nohibernate [HIBERNATION] Disable hibernation and resume.
2545
Thomas Gleixner79bf2bb2007-02-16 01:28:03 -08002546 nohz= [KNL] Boottime enable/disable dynamic ticks
2547 Valid arguments: on, off
2548 Default: on
2549
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002550 nohz_full= [KNL,BOOT]
Noam Camus2d13e6c2016-10-11 13:51:35 -07002551 The argument is a cpu list, as described above.
Frederic Weisbeckerc5bfece2013-04-12 16:45:34 +02002552 In kernels built with CONFIG_NO_HZ_FULL=y, set
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002553 the specified list of CPUs whose tick will be stopped
Frederic Weisbecker0453b432013-03-27 02:18:34 +01002554 whenever possible. The boot CPU will be forced outside
2555 the range to maintain the timekeeping.
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01002556 The CPUs in this range must also be included in the
2557 rcu_nocbs= set.
Frederic Weisbeckera8318812012-12-18 17:32:19 +01002558
Paul Mundteeee7852009-04-02 12:31:16 +09002559 noiotrap [SH] Disables trapped I/O port accesses.
2560
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002561 noirqdebug [X86-32] Disables the code which attempts to detect and
Linus Torvalds1da177e2005-04-16 15:20:36 -07002562 disable unhandled interrupt sources.
2563
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302564 no_timer_check [X86,APIC] Disables the code which tests for
Zachary Amsden8542b202006-12-07 02:14:09 +01002565 broken timer IRQ sources.
2566
Linus Torvalds1da177e2005-04-16 15:20:36 -07002567 noisapnp [ISAPNP] Disables ISA PnP code.
2568
2569 noinitrd [RAM] Tells the kernel not to load any configured
2570 initial RAM disk.
2571
Weidong Han03ea8152009-04-17 16:42:15 +08002572 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2573 remapping.
Chris Wrightd1423d52010-07-20 11:06:49 -07002574 [Deprecated - use intremap=off]
Weidong Han03ea8152009-04-17 16:42:15 +08002575
Linus Torvalds1da177e2005-04-16 15:20:36 -07002576 nointroute [IA-64]
2577
Andy Lutomirskid12a72b2016-01-29 11:42:58 -08002578 noinvpcid [X86] Disable the INVPCID cpu feature.
2579
Randy Dunlap16290242011-08-13 12:34:52 -07002580 nojitter [IA-64] Disables jitter checking for ITC timers.
Tony Luck0aa366f2007-07-20 11:22:30 -07002581
Jiri Kosina9cf4c4f2010-08-16 17:51:20 +02002582 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2583
Gleb Natapovfd10cde2010-10-14 11:22:51 +02002584 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2585 fault handling.
2586
Alexey Makhalov80e9a4f2016-10-28 00:54:32 -07002587 no-vmw-sched-clock
2588 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2589 clock and use the default one.
2590
Glauber Costad910f5c2011-07-11 15:28:19 -04002591 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2592 steal time is computed, but won't influence scheduler
2593 behaviour
2594
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002595 nolapic [X86-32,APIC] Do not enable or use the local APIC.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002596
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002597 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
Thomas Gleixnerad62ca22007-03-22 00:11:21 -08002598
Linus Torvalds1da177e2005-04-16 15:20:36 -07002599 noltlbs [PPC] Do not use large page/tlb entries for kernel
Christophe Leroyf15eea62016-02-09 17:07:52 +01002600 lowmem mapping on PPC40x and PPC8xx
Linus Torvalds1da177e2005-04-16 15:20:36 -07002601
Horms312f1f02006-02-22 09:57:55 +09002602 nomca [IA-64] Disable machine check abort handling
2603
Masanari Iida13696e02015-05-16 02:16:43 +09002604 nomce [X86-32] Disable Machine Check Exception
Hormsabe37e52006-04-01 01:36:09 +02002605
Andres Salomon83d73842007-10-12 23:04:06 +02002606 nomfgpt [X86-32] Disable Multi-Function General Purpose
2607 Timer usage (for AMD Geode machines).
2608
Don Zickusbda62632011-10-13 15:14:27 -04002609 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2610 shutdown the other cpus. Instead use the REBOOT_VECTOR
2611 irq.
2612
Dave Young02608be2012-02-01 10:33:14 +08002613 nomodule Disable module load
2614
Jiri Kosina016ddd92010-01-18 17:05:40 +01002615 nopat [X86] Disable PAT (page attribute table extension of
2616 pagetables) support.
2617
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002618 norandmaps Don't use address space randomization. Equivalent to
2619 echo 0 > /proc/sys/kernel/randomize_va_space
2620
Jiri Kosinabbff2162010-08-11 18:34:09 +02002621 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
Jeremy Fitzhardinge959b4fd2007-05-02 19:27:16 +02002622
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002623 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
Jeremy Fitzhardingeb7fb4af2007-05-02 19:27:13 +02002624 with UP alternatives
2625
H. Peter Anvin7a5091d2014-05-11 20:25:20 -07002626 nordrand [X86] Disable kernel use of the RDRAND and
2627 RDSEED instructions even if they are supported
2628 by the processor. RDRAND and RDSEED are still
2629 available to user space applications.
H. Peter Anvin49d859d2011-07-31 14:02:19 -07002630
Randy Dunlapa9913042005-10-23 12:57:11 -07002631 noresume [SWSUSP] Disables resume and restores original swap
2632 space.
2633
Linus Torvalds1da177e2005-04-16 15:20:36 -07002634 no-scroll [VGA] Disables scrollback.
2635 This is required for the Braillex ib80-piezo Braille
2636 reader made by F.H. Papenmeier (Germany).
2637
2638 nosbagart [IA-64]
2639
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002640 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
Chuck Ebbert4f886512006-03-23 02:59:34 -08002641
Len Brown61ec7562007-08-16 03:34:22 -04002642 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2643 and disable the IO APIC. legacy for "maxcpus=0".
Linus Torvalds1da177e2005-04-16 15:20:36 -07002644
Dave Jones97842212007-07-15 23:41:05 -07002645 nosoftlockup [KNL] Disable the soft-lockup detector.
2646
Linus Torvalds1da177e2005-04-16 15:20:36 -07002647 nosync [HW,M68K] Disables sync negotiation for all devices.
2648
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002649 notsc [BUGS=X86-32] Disable Time Stamp Counter
Linus Torvalds1da177e2005-04-16 15:20:36 -07002650
Ulrich Obergfell195daf62015-04-14 15:44:13 -07002651 nowatchdog [KNL] Disable both lockup detectors, i.e.
2652 soft-lockup and NMI watchdog (hard-lockup).
Don Zickus58687ac2010-05-07 17:11:44 -04002653
Linus Torvalds1da177e2005-04-16 15:20:36 -07002654 nowb [ARM]
Randy Dunlapa9913042005-10-23 12:57:11 -07002655
Weidong Han2b2fd872009-04-17 16:42:12 +08002656 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2657
Fenghua Yuf78cff42012-11-13 11:32:38 -08002658 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2659 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2660 Some features depend on CPU0. Known dependencies are:
2661 1. Resume from suspend/hibernate depends on CPU0.
2662 Suspend/hibernate will fail if CPU0 is offline and you
2663 need to online CPU0 before suspend/hibernate.
2664 2. PIC interrupts also depend on CPU0. CPU0 can't be
2665 removed if a PIC interrupt is detected.
2666 It's said poweroff/reboot may depend on CPU0 on some
2667 machines although I haven't seen such issues so far
2668 after CPU0 is offline on a few tested machines.
2669 If the dependencies are under your control, you can
2670 turn on cpu0_hotplug.
2671
Randy Dunlap16290242011-08-13 12:34:52 -07002672 nptcg= [IA-64] Override max number of concurrent global TLB
Fenghua Yua6c75b862008-03-14 13:57:08 -07002673 purges which is reported from either PAL_VM_SUMMARY or
2674 SAL PALO.
2675
Yinghai Lu2b633e32010-02-10 01:20:37 -08002676 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2677 could support. nr_cpus=n : n >= 1 limits the kernel to
Baoquan He7c142bf2016-08-24 13:06:45 +08002678 support 'n' processors. It could be larger than the
2679 number of already plugged CPU during bootup, later in
2680 runtime you can physically add extra cpu until it reaches
2681 n. So during boot up some boot time memory for per-cpu
2682 variables need be pre-allocated for later physical cpu
2683 hot plugging.
Yinghai Lu2b633e32010-02-10 01:20:37 -08002684
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07002685 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2686
Mel Gorman1a687c22012-11-22 11:16:36 +00002687 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2688 Allowed values are enable and disable
2689
KAMEZAWA Hiroyukif0c0b2b2007-07-15 23:38:01 -07002690 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2691 one of ['zone', 'node', 'default'] can be specified
2692 This can be set from sysctl after boot.
2693 See Documentation/sysctl/vm.txt for details.
2694
Randy Dunlap7c4be2532009-01-06 14:42:44 -08002695 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2696 See Documentation/debugging-via-ohci1394.txt for more
2697 info.
2698
Andres Salomon3ef0e1f2008-04-29 00:59:53 -07002699 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2700 Rather than timing out after 20 ms if an EC
2701 command is not properly ACKed, override the length
2702 of the timeout. We have interrupts disabled while
2703 waiting for the ACK, so if this is set too high
2704 interrupts *may* be lost!
2705
Tony Lindgren15ac7af2009-12-11 16:16:32 -08002706 omap_mux= [OMAP] Override bootloader pin multiplexing.
2707 Format: <mux_mode0.mode_name=value>...
2708 For example, to override I2C bus2:
2709 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2710
Linus Torvalds1da177e2005-04-16 15:20:36 -07002711 oprofile.timer= [HW]
2712 Use timer interrupt instead of performance counters
2713
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002714 oprofile.cpu_type= Force an oprofile cpu type
2715 This might be useful if you have an older oprofile
2716 userland or if you want common events.
Robert Richter8d7ff4f2009-06-23 11:48:14 +02002717 Format: { arch_perfmon }
2718 arch_perfmon: [X86] Force use of architectural
Robert Richter7e4e0bd2009-05-06 12:10:23 +02002719 perfmon on Intel CPUs instead of the
2720 CPU specific event set.
Robert Richter159a80b2011-10-11 19:39:16 +02002721 timer: [X86] Force use of architectural NMI
2722 timer mode (see also oprofile.timer
2723 for generic hr timer mode)
Andi Kleen1dcdb5a2009-04-27 17:44:11 +02002724
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002725 oops=panic Always panic on oopses. Default is to just kill the
2726 process, but there is a small probability of
2727 deadlocking the machine.
Olaf Heringd404ab02011-03-22 16:34:04 -07002728 This will also cause panics on machine check exceptions.
2729 Useful together with panic=30 to trigger a reboot.
2730
Randy Dunlapbcfde332010-06-07 17:10:38 -07002731 OSS [HW,OSS]
2732 See Documentation/sound/oss/oss-parameters.txt
2733
Joonsoo Kim48c96a32014-12-12 16:56:01 -08002734 page_owner= [KNL] Boot-time page_owner enabling option.
2735 Storage of the information about who allocated
2736 each page is disabled in default. With this switch,
2737 we can turn it on.
2738 on: enable the feature
2739
Laura Abbott8823b1d2016-03-15 14:56:27 -07002740 page_poison= [KNL] Boot-time parameter changing the state of
2741 poisoning on the buddy allocator.
2742 off: turn off poisoning
2743 on: turn on poisoning
2744
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07002745 panic= [KNL] Kernel behaviour on panic: delay <timeout>
Hugh Dickins4302fbc2011-07-26 16:08:52 -07002746 timeout > 0: seconds before rebooting
2747 timeout = 0: wait forever
2748 timeout < 0: reboot immediately
Linus Torvalds1da177e2005-04-16 15:20:36 -07002749 Format: <timeout>
2750
Prarit Bhargava9e3961a2014-12-10 15:45:50 -08002751 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2752 on a WARN().
2753
Masami Hiramatsuf06e5152014-06-06 14:37:07 -07002754 crash_kexec_post_notifiers
2755 Run kdump after running panic-notifiers and dumping
2756 kmsg. This only for the users who doubt kdump always
2757 succeeds in any situation.
2758 Note that this also increases risks of kdump failure,
2759 because some panic notifiers can make the crashed
2760 kernel more unstable.
2761
Linus Torvalds1da177e2005-04-16 15:20:36 -07002762 parkbd.port= [HW] Parallel port number the keyboard adapter is
2763 connected to, default is 0.
2764 Format: <parport#>
2765 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2766 0 for XT, 1 for AT (default is AT).
Randy Dunlapa9913042005-10-23 12:57:11 -07002767 Format: <mode>
Linus Torvalds1da177e2005-04-16 15:20:36 -07002768
Randy Dunlapa9913042005-10-23 12:57:11 -07002769 parport= [HW,PPT] Specify parallel ports. 0 disables.
2770 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2771 Use 'auto' to force the driver to use any
2772 IRQ/DMA settings detected (the default is to
2773 ignore detected IRQ/DMA settings because of
2774 possible conflicts). You can specify the base
2775 address, IRQ, and DMA settings; IRQ and DMA
2776 should be numbers, or 'auto' (for using detected
2777 settings on that particular port), or 'nofifo'
2778 (to avoid using a FIFO even if it is detected).
2779 Parallel ports are assigned in the order they
2780 are specified on the command line, starting
2781 with parport0.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002782
Randy Dunlapa9913042005-10-23 12:57:11 -07002783 parport_init_mode= [HW,PPT]
2784 Configure VIA parallel port to operate in
2785 a specific mode. This is necessary on Pegasos
2786 computer where firmware has no options for setting
2787 up parallel port mode and sets it to spp.
2788 Currently this function knows 686a and 8231 chips.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002789 Format: [spp|ps2|epp|ecp|ecpepp]
2790
Andrew Mortondd287792006-03-23 03:00:57 -08002791 pause_on_oops=
2792 Halt all CPUs after the first oops has been printed for
2793 the specified number of seconds. This is to be used if
2794 your oopses keep scrolling off the screen.
2795
Linus Torvalds1da177e2005-04-16 15:20:36 -07002796 pcbit= [HW,ISDN]
2797
2798 pcd. [PARIDE]
2799 See header of drivers/block/paride/pcd.c.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00002800 See also Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002801
Randy Dunlapa9913042005-10-23 12:57:11 -07002802 pci=option[,option...] [PCI] various PCI subsystem options:
Bjorn Helgaas1cc0ca22009-01-14 10:04:36 -07002803 earlydump [X86] dump PCI config space before the kernel
2804 changes anything
Andi Kleenc0115602008-08-22 09:53:39 +02002805 off [X86] don't probe for the PCI bus
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002806 bios [X86-32] force use of PCI BIOS, don't access
Randy Dunlapa9913042005-10-23 12:57:11 -07002807 the hardware directly. Use this if your machine
2808 has a non-standard PCI host bridge.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002809 nobios [X86-32] disallow use of PCI BIOS, only direct
Randy Dunlapa9913042005-10-23 12:57:11 -07002810 hardware access methods are allowed. Use this
2811 if you experience crashes upon bootup and you
2812 suspect they are caused by the BIOS.
Borislav Petkovafd8c082016-01-13 16:48:51 +01002813 conf1 [X86] Force use of PCI Configuration Access
2814 Mechanism 1 (config address in IO port 0xCF8,
2815 data in IO port 0xCFC, both 32-bit).
2816 conf2 [X86] Force use of PCI Configuration Access
2817 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2818 the function, IO port 0xCFA, also 8-bit, sets
2819 bus number. The config space is then accessed
2820 through ports 0xC000-0xCFFF).
2821 See http://wiki.osdev.org/PCI for more info
2822 on the configuration access mechanisms.
Randy Dunlap7f785762007-10-05 13:17:58 -07002823 noaer [PCIE] If the PCIEAER kernel config parameter is
2824 enabled, this kernel boot option can be used to
2825 disable the use of PCIE advanced error reporting.
Jeff Garzik32a2eea2007-10-11 16:57:27 -04002826 nodomains [PCI] Disable support for multiple PCI
2827 root domains (aka PCI segments, in ACPI-speak).
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05302828 nommconf [X86] Disable use of MMCONFIG for PCI
Bjorn Helgaas61be6d62006-02-15 15:17:43 -08002829 Configuration
Andreas Herrmann12983072009-06-07 16:15:16 +02002830 check_enable_amd_mmconf [X86] check for and enable
2831 properly configured MMIO access to PCI
2832 config space on AMD family 10h CPU
Matthew Wilcox309e57d2006-03-05 22:33:34 -07002833 nomsi [MSI] If the PCI_MSI kernel config parameter is
2834 enabled, this kernel boot option can be used to
2835 disable the use of MSI interrupts system-wide.
Stefan Assmanna9322f62008-06-11 16:35:14 +02002836 noioapicquirk [APIC] Disable all boot interrupt quirks.
2837 Safety option to keep boot IRQs enabled. This
2838 should never be necessary.
Stefan Assmann91979792008-06-11 16:35:15 +02002839 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2840 primary IO-APIC for bridges that cannot disable
2841 boot IRQs. This fixes a source of spurious IRQs
2842 when the system masks IRQs.
Stefan Assmann41b9eb22008-07-15 13:48:55 +02002843 noioapicreroute [APIC] Disable workaround that uses the
2844 boot IRQ equivalent of an IRQ that connects to
2845 a chipset where boot IRQs cannot be disabled.
2846 The opposite of ioapicreroute.
Alan Coxcd4f0ef2007-07-31 00:37:59 -07002847 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
Randy Dunlapa9913042005-10-23 12:57:11 -07002848 routing table. These calls are known to be buggy
2849 on several machines and they hang the machine
2850 when used, but on other computers it's the only
2851 way to get the interrupt routing table. Try
2852 this option if the kernel is unable to allocate
2853 IRQs or discover secondary PCI buses on your
2854 motherboard.
Andi Kleenc0115602008-08-22 09:53:39 +02002855 rom [X86] Assign address space to expansion ROMs.
Randy Dunlapa9913042005-10-23 12:57:11 -07002856 Use with caution as certain devices share
2857 address decoders between ROMs and other
2858 resources.
Andi Kleenc0115602008-08-22 09:53:39 +02002859 norom [X86] Do not assign address space to
Gary Hadebb71ad82008-05-12 13:57:46 -07002860 expansion ROMs that do not already have
2861 BIOS assigned address ranges.
Mike Habeck7bd1c362010-05-12 11:14:32 -07002862 nobar [X86] Do not assign address space to the
2863 BARs that weren't assigned by the BIOS.
Andi Kleenc0115602008-08-22 09:53:39 +02002864 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
Randy Dunlapa9913042005-10-23 12:57:11 -07002865 assigned automatically to PCI devices. You can
2866 make the kernel exclude IRQs of your ISA cards
2867 this way.
Andi Kleenc0115602008-08-22 09:53:39 +02002868 pirqaddr=0xAAAAA [X86] Specify the physical address
Randy Dunlapa9913042005-10-23 12:57:11 -07002869 of the PIRQ table (normally generated
2870 by the BIOS) if it is outside the
2871 F0000h-100000h range.
Andi Kleenc0115602008-08-22 09:53:39 +02002872 lastbus=N [X86] Scan all buses thru bus #N. Can be
Randy Dunlapa9913042005-10-23 12:57:11 -07002873 useful if the kernel is unable to find your
2874 secondary buses and you want to tell it
2875 explicitly which ones they are.
Andi Kleenc0115602008-08-22 09:53:39 +02002876 assign-busses [X86] Always assign all PCI bus
Randy Dunlapa9913042005-10-23 12:57:11 -07002877 numbers ourselves, overriding
2878 whatever the firmware may have done.
Andi Kleenc0115602008-08-22 09:53:39 +02002879 usepirqmask [X86] Honor the possible IRQ mask stored
Randy Dunlapa9913042005-10-23 12:57:11 -07002880 in the BIOS $PIR table. This is needed on
2881 some systems with broken BIOSes, notably
2882 some HP Pavilion N5400 and Omnibook XE3
2883 notebooks. This will have no effect if ACPI
2884 IRQ routing is enabled.
Andi Kleenc0115602008-08-22 09:53:39 +02002885 noacpi [X86] Do not use ACPI for IRQ routing
Randy Dunlapa9913042005-10-23 12:57:11 -07002886 or for PCI scanning.
Bjorn Helgaas7bc5e3f2010-02-23 10:24:41 -07002887 use_crs [X86] Use PCI host bridge window information
2888 from ACPI. On BIOSes from 2008 or later, this
2889 is enabled by default. If you need to use this,
2890 please report a bug.
2891 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2892 If you need to use this, please report a bug.
Randy Dunlapa9913042005-10-23 12:57:11 -07002893 routeirq Do IRQ routing for all PCI devices.
2894 This is normally done in pci_enable_device(),
2895 so this option is a temporary workaround
2896 for broken drivers that don't call it.
Yinghai Lu13a6ddb2008-03-27 01:31:18 -07002897 skip_isa_align [X86] do not align io start addr, so can
2898 handle more pci cards
Andi Kleen0637a702006-09-26 10:52:41 +02002899 noearly [X86] Don't do any early type 1 scanning.
2900 This might help on some broken boards which
2901 machine check when some devices' config space
2902 is read. But various workarounds are disabled
2903 and some IOMMU drivers will not work.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002904 bfsort Sort PCI devices into breadth-first order.
2905 This sorting is done to get a device
2906 order compatible with older (<= 2.4) kernels.
2907 nobfsort Don't sort PCI devices into breadth-first order.
Yijing Wangfa238712013-01-30 09:40:52 +08002908 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2909 tuning and use the BIOS-configured MPS defaults.
2910 pcie_bus_safe Set every device's MPS to the largest value
2911 supported by all devices below the root complex.
2912 pcie_bus_perf Set device MPS to the largest allowable MPS
2913 based on its parent bus. Also set MRRS (Max
2914 Read Request Size) to the largest supported
2915 value (no larger than the MPS that the device
2916 or bus can support) for best performance.
2917 pcie_bus_peer2peer Set every device's MPS to 128B, which
2918 every device is guaranteed to support. This
2919 configuration allows peer-to-peer DMA between
2920 any pair of devices, possibly at the cost of
2921 reduced performance. This also guarantees
2922 that hot-added devices will work.
Atsushi Nemoto4516a612007-02-05 16:36:06 -08002923 cbiosize=nn[KMG] The fixed amount of bus space which is
2924 reserved for the CardBus bridge's IO window.
2925 The default value is 256 bytes.
2926 cbmemsize=nn[KMG] The fixed amount of bus space which is
2927 reserved for the CardBus bridge's memory
2928 window. The default value is 64 megabytes.
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002929 resource_alignment=
2930 Format:
2931 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
Koehrer Mathias (ETAS/ESW5)644a5442016-06-07 14:24:17 +00002932 [<order of align>@]pci:<vendor>:<device>\
2933 [:<subvendor>:<subdevice>][; ...]
Yuji Shimada32a9a6822009-03-16 17:13:39 +09002934 Specifies alignment and device to reassign
2935 aligned memory resources.
2936 If <order of align> is not specified,
2937 PAGE_SIZE is used as alignment.
2938 PCI-PCI bridge can be specified, if resource
2939 windows need to be expanded.
Mathias Koehrer8b078c62016-08-09 10:33:31 +02002940 To specify the alignment for several
2941 instances of a device, the PCI vendor,
2942 device, subvendor, and subdevice may be
2943 specified, e.g., 4096@pci:8086:9c22:103c:198f
Andrew Patterson43c16402009-04-22 16:52:09 -06002944 ecrc= Enable/disable PCIe ECRC (transaction layer
2945 end-to-end CRC checking).
2946 bios: Use BIOS/firmware settings. This is the
2947 the default.
2948 off: Turn ECRC off
2949 on: Turn ECRC on.
Yijing Wang8c8803c2013-01-23 20:29:06 +08002950 hpiosize=nn[KMG] The fixed amount of bus space which is
2951 reserved for hotplug bridge's IO window.
2952 Default size is 256 bytes.
2953 hpmemsize=nn[KMG] The fixed amount of bus space which is
2954 reserved for hotplug bridge's memory window.
2955 Default size is 2 megabytes.
Keith Busche16b4662016-07-21 21:40:28 -06002956 hpbussize=nn The minimum amount of additional bus numbers
2957 reserved for buses below a hotplug bridge.
2958 Default is 1.
Yinghai Lub55438f2012-02-23 19:23:30 -08002959 realloc= Enable/disable reallocating PCI bridge resources
2960 if allocations done by BIOS are too small to
2961 accommodate resources required by all child
2962 devices.
2963 off: Turn realloc off
2964 on: Turn realloc on
2965 realloc same as realloc=on
Rafael J. Wysocki6748dcc2012-03-01 00:06:33 +01002966 noari do not use PCIe ARI.
Bjorn Helgaas284f5f92012-04-30 15:21:02 -06002967 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2968 only look for one device below a PCIe downstream
2969 port.
Matt Domsch6b4b78f2006-09-29 15:23:23 -05002970
Chuck Ebberte5665a42008-09-24 20:40:34 -04002971 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2972 Management.
2973 off Disable ASPM.
2974 force Enable ASPM even on devices that claim not to support it.
2975 WARNING: Forcing ASPM on may cause system lockups.
2976
MUNEDA Takahiro7570a332012-02-02 11:09:22 -05002977 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2978 nomsi Do not use MSI for PCI Express Native Hotplug (this
2979 makes all PCIe ports use INTx for hotplug services).
2980
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002981 pcie_ports= [PCIE] PCIe ports handling:
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002982 auto Ask the BIOS whether or not to use native PCIe services
2983 associated with PCIe ports (PME, hot-plug, AER). Use
2984 them only if that is allowed by the BIOS.
2985 native Use native PCIe services associated with PCIe ports
2986 unconditionally.
Rafael J. Wysocki79dd9182010-08-21 01:51:44 +02002987 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2988 ports driver.
2989
Mika Westerberg9d26d3a2016-06-02 11:17:12 +03002990 pcie_port_pm= [PCIE] PCIe port power management handling:
2991 off Disable power management of all PCIe ports
2992 force Forcibly enable power management of all PCIe ports
2993
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002994 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
Rafael J. Wysockic39fae12010-02-17 23:40:07 +01002995 nomsi Do not use MSI for native PCIe PME signaling (this makes
Rafael J. Wysocki28eb5f22010-08-21 22:02:38 +02002996 all PCIe root ports use INTx for all services).
Rafael J. Wysockic7f48652010-02-17 23:39:08 +01002997
Linus Torvalds1da177e2005-04-16 15:20:36 -07002998 pcmv= [HW,PCMCIA] BadgePAD 4
2999
Tushar Behera39ac5ba2014-03-28 10:50:21 +05303000 pd_ignore_unused
3001 [PM]
3002 Keep all power-domains already enabled by bootloader on,
3003 even if no driver has claimed them. This is useful
3004 for debug and development, but should not be
3005 needed on a platform with proper driver support.
3006
Linus Torvalds1da177e2005-04-16 15:20:36 -07003007 pd. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003008 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003009
3010 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3011 boot time.
3012 Format: { 0 | 1 }
3013 See arch/parisc/kernel/pdc_chassis.c
3014
Tejun Heof58dc012009-08-14 15:00:50 +09003015 percpu_alloc= Select which percpu first chunk allocator to use.
Tejun Heoe933a732009-08-14 15:00:53 +09003016 Currently supported values are "embed" and "page".
3017 Archs may support subset or none of the selections.
3018 See comments in mm/percpu.c for details on each
3019 allocator. This parameter is primarily for debugging
3020 and performance comparison.
Tejun Heofa8a7092009-06-22 11:56:24 +09003021
Linus Torvalds1da177e2005-04-16 15:20:36 -07003022 pf. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003023 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003024
3025 pg. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003026 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003027
3028 pirq= [SMP,APIC] Manual mp-table setup
Uwe Hermann71cced62008-10-20 09:32:21 -07003029 See Documentation/x86/i386/IO-APIC.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003030
3031 plip= [PPT,NET] Parallel port network link
3032 Format: { parport<nr> | timid | 0 }
3033 See also Documentation/parport.txt.
3034
Randy Dunlap16290242011-08-13 12:34:52 -07003035 pmtmr= [X86] Manual setup of pmtmr I/O Port.
Thomas Gleixnerde32a242008-07-12 05:33:30 +02003036 Override pmtimer IOPort with a hex value.
3037 e.g. pmtmr=0x508
3038
Bjorn Helgaas96242112011-08-11 12:14:05 -06003039 pnp.debug=1 [PNP]
3040 Enable PNP debug messages (depends on the
3041 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3042 via /sys/module/pnp/parameters/debug. We always show
3043 current resource usage; turning this on also shows
3044 possible settings and some assignment information.
Bjorn Helgaas97ef0622008-08-19 16:53:41 -06003045
Linus Torvalds1da177e2005-04-16 15:20:36 -07003046 pnpacpi= [ACPI]
3047 { off }
3048
3049 pnpbios= [ISAPNP]
3050 { on | off | curr | res | no-curr | no-res }
3051
3052 pnp_reserve_irq=
3053 [ISAPNP] Exclude IRQs for the autoconfiguration
3054
3055 pnp_reserve_dma=
3056 [ISAPNP] Exclude DMAs for the autoconfiguration
3057
3058 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
Randy Dunlapa9913042005-10-23 12:57:11 -07003059 Ranges are in pairs (I/O port base and size).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003060
3061 pnp_reserve_mem=
Randy Dunlapa9913042005-10-23 12:57:11 -07003062 [ISAPNP] Exclude memory regions for the
3063 autoconfiguration.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003064 Ranges are in pairs (memory base and size).
3065
Randy Dunlap4af94f32009-04-17 18:30:28 -07003066 ports= [IP_VS_FTP] IPVS ftp helper module
3067 Default is 21.
3068 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3069 may be specified.
3070 Format: <port>,<port>....
3071
Balbir Singhc3cbd072016-12-02 00:08:26 +11003072 powersave=off [PPC] This option disables power saving features.
3073 It specifically disables cpuidle and sets the
3074 platform machine description specific power_save
3075 function to NULL. On Idle the CPU just reduces
3076 execution priority.
3077
Anton Blanchard3eb5d582015-10-29 11:44:06 +11003078 ppc_strict_facility_enable
3079 [PPC] This option catches any kernel floating point,
3080 Altivec, VSX and SPE outside of regions specifically
3081 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3082 There is some performance impact when enabling this.
3083
Ingo Molnar45807a12007-07-15 23:40:10 -07003084 print-fatal-signals=
3085 [KNL] debug: print fatal signals
Naohiro Ooiwaf84d49b2009-11-09 00:46:42 +09003086
3087 If enabled, warn about various signal handling
3088 related application anomalies: too many signals,
3089 too many POSIX.1 timers, fatal signals causing a
3090 coredump - etc.
3091
3092 If you hit the warning due to signal overflow,
3093 you might want to try "ulimit -i unlimited".
3094
Ingo Molnar45807a12007-07-15 23:40:10 -07003095 default: off.
3096
Matthew Garrettc22ab332012-03-05 14:59:10 -08003097 printk.always_kmsg_dump=
3098 Trigger kmsg_dump for cases other than kernel oops or
3099 panics
3100 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3101 default: disabled
3102
Borislav Petkov750afe72016-08-02 14:04:07 -07003103 printk.devkmsg={on,off,ratelimit}
3104 Control writing to /dev/kmsg.
3105 on - unlimited logging to /dev/kmsg from userspace
3106 off - logging to /dev/kmsg disabled
3107 ratelimit - ratelimit the logging
3108 Default: ratelimit
3109
Randy Dunlape84845c2007-07-15 23:40:25 -07003110 printk.time= Show timing data prefixed to each printk message line
3111 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3112
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003113 processor.max_cstate= [HW,ACPI]
3114 Limit processor to maximum C-state
3115 max_cstate=9 overrides any DMI blacklist limit.
3116
3117 processor.nocst [HW,ACPI]
3118 Ignore the _CST method to determine C-states,
3119 instead using the legacy FADT method
3120
Linus Torvalds1da177e2005-04-16 15:20:36 -07003121 profile= [KNL] Enable kernel profiling via /proc/profile
Randy Dunlapa9913042005-10-23 12:57:11 -07003122 Format: [schedule,]<number>
3123 Param: "schedule" - profile schedule points.
3124 Param: <number> - step/bucket size as a power of 2 for
3125 statistical time based profiling.
Mel Gormanb3da2a72007-10-24 18:23:50 +02003126 Param: "sleep" - profile D-state sleeping (millisecs).
3127 Requires CONFIG_SCHEDSTATS
Dave Jonesc0fe2e62007-10-20 03:08:22 +02003128 Param: "kvm" - profile VM exits.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003129
Linus Torvalds1da177e2005-04-16 15:20:36 -07003130 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3131 before loading.
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003132 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003133
Randy Dunlapa9913042005-10-23 12:57:11 -07003134 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3135 probe for; one of (bare|imps|exps|lifebook|any).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003136 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3137 per second.
Randy Dunlapa9913042005-10-23 12:57:11 -07003138 psmouse.resetafter= [HW,MOUSE]
3139 Try to reset the device after so many bad packets
Linus Torvalds1da177e2005-04-16 15:20:36 -07003140 (0 = never).
3141 psmouse.resolution=
3142 [HW,MOUSE] Set desired mouse resolution, in dpi.
3143 psmouse.smartscroll=
Randy Dunlapa9913042005-10-23 12:57:11 -07003144 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003145 0 = disabled, 1 = enabled (default).
3146
Matthew Garrettdee28e72011-07-21 16:57:55 -04003147 pstore.backend= Specify the name of the pstore backend to use
3148
Linus Torvalds1da177e2005-04-16 15:20:36 -07003149 pt. [PARIDE]
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003150 See Documentation/blockdev/paride.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003151
Kay Sieversdc8c8582007-08-15 12:25:38 +02003152 pty.legacy_count=
3153 [KNL] Number of legacy pty's. Overwrites compiled-in
3154 default number.
3155
Randy Dunlap7d2c5022006-09-29 02:01:02 -07003156 quiet [KNL] Disable most log messages
Randy Dunlapa9913042005-10-23 12:57:11 -07003157
Linus Torvalds1da177e2005-04-16 15:20:36 -07003158 r128= [HW,DRM]
3159
3160 raid= [HW,RAID]
Jani Nikulae52347b2016-11-03 12:10:10 +02003161 See Documentation/admin-guide/md.rst.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003162
Linus Torvalds1da177e2005-04-16 15:20:36 -07003163 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
Randy Dunlap31c00fc2008-11-13 21:33:24 +00003164 See Documentation/blockdev/ramdisk.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003165
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003166 rcu_nocbs= [KNL]
Noam Camus2d13e6c2016-10-11 13:51:35 -07003167 The argument is a cpu list, as described above.
3168
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003169 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3170 the specified list of CPUs to be no-callback CPUs.
3171 Invocation of these CPUs' RCU callbacks will
Paul E. McKenneya4889852012-12-03 08:16:28 -08003172 be offloaded to "rcuox/N" kthreads created for
3173 that purpose, where "x" is "b" for RCU-bh, "p"
3174 for RCU-preempt, and "s" for RCU-sched, and "N"
3175 is the CPU number. This reduces OS jitter on the
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003176 offloaded CPUs, which can be useful for HPC and
3177 real-time workloads. It can also improve energy
3178 efficiency for asymmetric multiprocessors.
3179
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003180 rcu_nocb_poll [KNL]
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003181 Rather than requiring that offloaded CPUs
3182 (specified by rcu_nocbs= above) explicitly
3183 awaken the corresponding "rcuoN" kthreads,
3184 make these kthreads poll for callbacks.
3185 This improves the real-time response for the
3186 offloaded CPUs by relieving them of the need to
3187 wake up the corresponding kthread, but degrades
3188 energy efficiency by requiring that the kthreads
3189 periodically wake up to do the polling.
3190
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003191 rcutree.blimit= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003192 Set maximum number of finished RCU callbacks to
3193 process in one batch.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003194
Paul E. McKenneya3dc2942015-04-20 11:40:50 -07003195 rcutree.dump_tree= [KNL]
3196 Dump the structure of the rcu_node combining tree
3197 out at early boot. This is used for diagnostic
3198 purposes, to verify correct tree setup.
3199
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003200 rcutree.gp_cleanup_delay= [KNL]
3201 Set the number of jiffies to delay each step of
3202 RCU grace-period cleanup. This only has effect
3203 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3204
Paul E. McKenney37745d22015-01-22 18:24:08 -08003205 rcutree.gp_init_delay= [KNL]
3206 Set the number of jiffies to delay each step of
3207 RCU grace-period initialization. This only has
Paul E. McKenney0f41c0d2015-03-10 18:33:20 -07003208 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3209 is set.
3210
3211 rcutree.gp_preinit_delay= [KNL]
3212 Set the number of jiffies to delay each step of
3213 RCU grace-period pre-initialization, that is,
3214 the propagation of recent CPU-hotplug changes up
3215 the rcu_node combining tree. This only has effect
3216 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
Paul E. McKenney37745d22015-01-22 18:24:08 -08003217
Paul E. McKenney7fa27002015-04-20 10:27:15 -07003218 rcutree.rcu_fanout_exact= [KNL]
3219 Disable autobalancing of the rcu_node combining
3220 tree. This is used by rcutorture, and might
3221 possibly be useful for architectures having high
3222 cache-to-cache transfer latencies.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003223
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003224 rcutree.rcu_fanout_leaf= [KNL]
Paul E. McKenneyee968ac2015-07-31 08:28:35 -07003225 Change the number of CPUs assigned to each
3226 leaf rcu_node structure. Useful for very
3227 large systems, which will choose the value 64,
3228 and for NUMA systems with large remote-access
3229 latencies, which will choose a value aligned
3230 with the appropriate hardware boundaries.
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003231
Paul E. McKenney4a81e832014-06-20 16:49:01 -07003232 rcutree.jiffies_till_sched_qs= [KNL]
3233 Set required age in jiffies for a
3234 given grace period before RCU starts
3235 soliciting quiescent-state help from
3236 rcu_note_context_switch().
3237
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003238 rcutree.jiffies_till_first_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003239 Set delay from grace-period initialization to
3240 first attempt to force quiescent states.
3241 Units are jiffies, minimum value is zero,
3242 and maximum value is HZ.
3243
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003244 rcutree.jiffies_till_next_fqs= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003245 Set delay between subsequent attempts to force
3246 quiescent states. Units are jiffies, minimum
3247 value is one, and maximum value is HZ.
3248
Clark Williams21871d72014-09-12 21:21:09 -05003249 rcutree.kthread_prio= [KNL,BOOT]
Paul E. McKenneyd2af1ad2015-01-20 23:54:59 -08003250 Set the SCHED_FIFO priority of the RCU per-CPU
3251 kthreads (rcuc/N). This value is also used for
3252 the priority of the RCU boost threads (rcub/N)
3253 and for the RCU grace-period kthreads (rcu_bh,
3254 rcu_preempt, and rcu_sched). If RCU_BOOST is
3255 set, valid values are 1-99 and the default is 1
3256 (the least-favored priority). Otherwise, when
3257 RCU_BOOST is not set, valid values are 0-99 and
3258 the default is zero (non-realtime operation).
Clark Williams21871d72014-09-12 21:21:09 -05003259
Paul E. McKenneyfbce7492014-06-24 09:26:11 -07003260 rcutree.rcu_nocb_leader_stride= [KNL]
3261 Set the number of NOCB kthread groups, which
3262 defaults to the square root of the number of
3263 CPUs. Larger numbers reduces the wakeup overhead
3264 on the per-CPU grace-period kthreads, but increases
3265 that same overhead on each group's leader.
3266
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003267 rcutree.qhimark= [KNL]
Paul E. McKenney97e63f02013-10-27 09:44:03 -07003268 Set threshold of queued RCU callbacks beyond which
3269 batch limiting is disabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003270
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003271 rcutree.qlowmark= [KNL]
Robert P. J. Day24aaef82008-02-03 15:20:26 +02003272 Set threshold of queued RCU callbacks below which
3273 batch limiting is re-enabled.
Dipankar Sarma21a1ea92006-03-07 21:55:33 -08003274
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003275 rcutree.rcu_idle_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003276 Set wakeup interval for idle CPUs that have
3277 RCU callbacks (RCU_FAST_NO_HZ=y).
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003278
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003279 rcutree.rcu_idle_lazy_gp_delay= [KNL]
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003280 Set wakeup interval for idle CPUs that have
3281 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3282 Lazy RCU callbacks are those which RCU can
3283 prove do nothing more than free memory.
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07003284
Paul E. McKenneye3c50df2017-01-06 15:14:11 -08003285 rcutree.rcu_kick_kthreads= [KNL]
3286 Cause the grace-period kthread to get an extra
3287 wake_up() if it sleeps three times longer than
3288 it should at force-quiescent-state time.
3289 This wake_up() will be accompanied by a
3290 WARN_ONCE() splat and an ftrace_dump().
3291
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003292 rcuperf.gp_exp= [KNL]
3293 Measure performance of expedited synchronous
3294 grace-period primitives.
3295
Paul E. McKenneydf37e662016-01-30 20:56:38 -08003296 rcuperf.holdoff= [KNL]
3297 Set test-start holdoff period. The purpose of
3298 this parameter is to delay the start of the
3299 test until boot completes in order to avoid
3300 interference.
3301
Paul E. McKenneybdea9e32016-01-01 13:47:19 -08003302 rcuperf.nreaders= [KNL]
3303 Set number of RCU readers. The value -1 selects
3304 N, where N is the number of CPUs. A value
3305 "n" less than -1 selects N-n+1, where N is again
3306 the number of CPUs. For example, -2 selects N
3307 (the number of CPUs), -3 selects N+1, and so on.
3308 A value of "n" less than or equal to -N selects
3309 a single reader.
3310
3311 rcuperf.nwriters= [KNL]
3312 Set number of RCU writers. The values operate
3313 the same as for rcuperf.nreaders.
3314 N, where N is the number of CPUs
3315
3316 rcuperf.perf_runnable= [BOOT]
3317 Start rcuperf running at boot time.
3318
3319 rcuperf.shutdown= [KNL]
3320 Shut the system down after performance tests
3321 complete. This is useful for hands-off automated
3322 testing.
3323
3324 rcuperf.perf_type= [KNL]
3325 Specify the RCU implementation to test.
3326
3327 rcuperf.verbose= [KNL]
3328 Enable additional printk() statements.
3329
Paul E. McKenney38706bc2014-08-18 21:12:17 -07003330 rcutorture.cbflood_inter_holdoff= [KNL]
3331 Set holdoff time (jiffies) between successive
3332 callback-flood tests.
3333
3334 rcutorture.cbflood_intra_holdoff= [KNL]
3335 Set holdoff time (jiffies) between successive
3336 bursts of callbacks within a given callback-flood
3337 test.
3338
3339 rcutorture.cbflood_n_burst= [KNL]
3340 Set the number of bursts making up a given
3341 callback-flood test. Set this to zero to
3342 disable callback-flood testing.
3343
3344 rcutorture.cbflood_n_per_burst= [KNL]
3345 Set the number of callbacks to be registered
3346 in a given burst of a callback-flood test.
3347
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003348 rcutorture.fqs_duration= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003349 Set duration of force_quiescent_state bursts
3350 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003351
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003352 rcutorture.fqs_holdoff= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003353 Set holdoff time within force_quiescent_state bursts
3354 in microseconds.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003355
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003356 rcutorture.fqs_stutter= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003357 Set wait time between force_quiescent_state bursts
3358 in seconds.
3359
3360 rcutorture.gp_cond= [KNL]
3361 Use conditional/asynchronous update-side
3362 primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003363
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003364 rcutorture.gp_exp= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003365 Use expedited update-side primitives, if available.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003366
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003367 rcutorture.gp_normal= [KNL]
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003368 Use normal (non-expedited) asynchronous
3369 update-side primitives, if available.
3370
3371 rcutorture.gp_sync= [KNL]
3372 Use normal (non-expedited) synchronous
3373 update-side primitives, if available. If all
3374 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3375 rcutorture.gp_normal=, and rcutorture.gp_sync=
3376 are zero, rcutorture acts as if is interpreted
3377 they are all non-zero.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003378
3379 rcutorture.n_barrier_cbs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003380 Set callbacks/threads for rcu_barrier() testing.
3381
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003382 rcutorture.nfakewriters= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003383 Set number of concurrent RCU writers. These just
3384 stress RCU, they don't participate in the actual
3385 test, hence the "fake".
3386
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003387 rcutorture.nreaders= [KNL]
Paul E. McKenney3838cc12015-03-12 13:55:48 -07003388 Set number of RCU readers. The value -1 selects
3389 N-1, where N is the number of CPUs. A value
3390 "n" less than -1 selects N-n-2, where N is again
3391 the number of CPUs. For example, -2 selects N
3392 (the number of CPUs), -3 selects N+1, and so on.
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003393
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003394 rcutorture.object_debug= [KNL]
3395 Enable debug-object double-call_rcu() testing.
3396
3397 rcutorture.onoff_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003398 Set time (s) after boot for CPU-hotplug testing.
3399
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003400 rcutorture.onoff_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003401 Set time (s) between CPU-hotplug operations, or
3402 zero to disable CPU-hotplug testing.
3403
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003404 rcutorture.shuffle_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003405 Set task-shuffle interval (s). Shuffling tasks
3406 allows some CPUs to go into dyntick-idle mode
3407 during the rcutorture test.
3408
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003409 rcutorture.shutdown_secs= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003410 Set time (s) after boot system shutdown. This
3411 is useful for hands-off automated testing.
3412
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003413 rcutorture.stall_cpu= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003414 Duration of CPU stall (s) to test RCU CPU stall
3415 warnings, zero to disable.
3416
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003417 rcutorture.stall_cpu_holdoff= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003418 Time to wait (s) after boot before inducing stall.
3419
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003420 rcutorture.stat_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003421 Time (s) between statistics printk()s.
3422
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003423 rcutorture.stutter= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003424 Time (s) to stutter testing, for example, specifying
3425 five seconds causes the test to run for five seconds,
3426 wait for five seconds, and so on. This tests RCU's
3427 ability to transition abruptly to and from idle.
3428
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003429 rcutorture.test_boost= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003430 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3431 "Maybe" means test if the RCU implementation
3432 under test support RCU priority boosting.
3433
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003434 rcutorture.test_boost_duration= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003435 Duration (s) of each individual boost test.
3436
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003437 rcutorture.test_boost_interval= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003438 Interval (s) between each boost test.
3439
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003440 rcutorture.test_no_idle_hz= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003441 Test RCU's dyntick-idle handling. See also the
3442 rcutorture.shuffle_interval parameter.
3443
Paul E. McKenney21b05de2015-05-14 17:29:51 -07003444 rcutorture.torture_runnable= [BOOT]
3445 Start rcutorture running at boot time.
3446
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003447 rcutorture.torture_type= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003448 Specify the RCU implementation to test.
3449
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003450 rcutorture.verbose= [KNL]
Paul E. McKenneydabb8aa2012-04-23 10:54:45 -07003451 Enable additional printk() statements.
3452
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003453 rcupdate.rcu_cpu_stall_suppress= [KNL]
3454 Suppress RCU CPU stall warning messages.
3455
3456 rcupdate.rcu_cpu_stall_timeout= [KNL]
3457 Set timeout for RCU CPU stall warning messages.
3458
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003459 rcupdate.rcu_expedited= [KNL]
3460 Use expedited grace-period primitives, for
3461 example, synchronize_rcu_expedited() instead
3462 of synchronize_rcu(). This reduces latency,
3463 but can increase CPU utilization, degrade
3464 real-time latency, and degrade energy efficiency.
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003465 No effect on CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003466
Paul E. McKenney5a9be7c2015-11-24 15:44:06 -08003467 rcupdate.rcu_normal= [KNL]
3468 Use only normal grace-period primitives,
3469 for example, synchronize_rcu() instead of
3470 synchronize_rcu_expedited(). This improves
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003471 real-time latency, CPU utilization, and
3472 energy efficiency, but can expose users to
3473 increased grace-period latency. This parameter
3474 overrides rcupdate.rcu_expedited. No effect on
3475 CONFIG_TINY_RCU kernels.
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003476
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003477 rcupdate.rcu_normal_after_boot= [KNL]
3478 Once boot has completed (that is, after
3479 rcu_end_inkernel_boot() has been invoked), use
Paul E. McKenney79cfea02015-12-07 13:09:52 -08003480 only normal grace-period primitives. No effect
3481 on CONFIG_TINY_RCU kernels.
Paul E. McKenney3e42ec12015-11-25 18:56:00 -08003482
Paul E. McKenney52db30a2014-07-01 18:16:30 -07003483 rcupdate.rcu_task_stall_timeout= [KNL]
3484 Set timeout in jiffies for RCU task stall warning
3485 messages. Disable with a value less than or equal
3486 to zero.
3487
Pranith Kumar74860fe2014-09-19 11:34:09 -04003488 rcupdate.rcu_self_test= [KNL]
3489 Run the RCU early boot self tests
3490
3491 rcupdate.rcu_self_test_bh= [KNL]
3492 Run the RCU bh early boot self tests
3493
3494 rcupdate.rcu_self_test_sched= [KNL]
3495 Run the RCU sched early boot self tests
3496
Olof Johanssonffdfc402005-09-06 15:17:19 -07003497 rdinit= [KNL]
3498 Format: <full_path>
3499 Run specified binary instead of /init from the ramdisk,
3500 used for early userspace startup. See initrd.
3501
Robin Holt1b3a5d02013-07-08 16:01:42 -07003502 reboot= [KNL]
3503 Format (x86 or x86_64):
3504 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3505 [[,]s[mp]#### \
3506 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3507 [[,]f[orce]
3508 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3509 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3510 reboot_force is either force or not specified,
3511 reboot_cpu is s[mp]#### with #### being the processor
3512 to be used for rebooting.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003513
Paul Jackson46b6d942008-07-04 10:00:09 -07003514 relax_domain_level=
3515 [KNL, SMP] Set scheduler's default relax_domain_level.
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003516 See Documentation/cgroup-v1/cpusets.txt.
Paul Jackson46b6d942008-07-04 10:00:09 -07003517
Linus Torvalds1da177e2005-04-16 15:20:36 -07003518 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3519
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003520 reservetop= [X86-32]
Zachary Amsden461a9af2006-09-25 23:32:25 -07003521 Format: nn[KMG]
3522 Reserves a hole at the top of the kernel virtual
3523 address space.
3524
H. Peter Anvin9ea77bd2010-08-25 16:38:20 -07003525 reservelow= [X86]
3526 Format: nn[K]
3527 Set the amount of memory to reserve for BIOS at
3528 the bottom of the address space.
3529
Vivek Goyal7e962872006-09-27 01:50:44 -07003530 reset_devices [KNL] Force drivers to reset the underlying device
3531 during initialization.
3532
Randy Dunlapa9913042005-10-23 12:57:11 -07003533 resume= [SWSUSP]
3534 Specify the partition device for software suspend
Minho Ban2df83fa2012-05-14 21:45:31 +02003535 Format:
3536 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003537
Rafael J. Wysockiecbd0da2006-12-06 20:34:13 -08003538 resume_offset= [SWSUSP]
3539 Specify the offset from the beginning of the partition
3540 given by "resume=" at which the swap header is located,
3541 in <PAGE_SIZE> units (needed only for swap files).
3542 See Documentation/power/swsusp-and-swap-files.txt
3543
Barry Songf126f732011-10-10 23:38:41 +02003544 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3545 read the resume files
3546
Barry Song6f8d7022011-10-06 20:34:46 +02003547 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3548 Useful for devices that are detected asynchronously
3549 (e.g. USB and MMC devices).
3550
Bojan Smojverf996fc92010-09-09 23:06:23 +02003551 hibernate= [HIBERNATION]
3552 noresume Don't check if there's a hibernation image
3553 present during boot.
3554 nocompress Don't compress/decompress hibernation images.
Kees Cooka6e15a32014-06-13 13:30:35 -07003555 no Disable hibernation and resume.
Rafael J. Wysocki4c0b6c12016-07-10 02:12:10 +02003556 protect_image Turn on image protection during restoration
3557 (that will set all pages holding image data
3558 during restoration read-only).
Bojan Smojverf996fc92010-09-09 23:06:23 +02003559
Michael Neuling0a7b35cb2007-02-10 01:44:33 -08003560 retain_initrd [RAM] Keep initrd memory after extraction
3561
Andrew Clausen0efbb782015-01-09 20:24:55 +00003562 rfkill.default_state=
3563 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3564 etc. communication is blocked by default.
3565 1 Unblocked.
3566
3567 rfkill.master_switch_mode=
3568 0 The "airplane mode" button does nothing.
3569 1 The "airplane mode" button toggles between everything
3570 blocked and the previous configuration.
3571 2 The "airplane mode" button toggles between everything
3572 blocked and everything unblocked.
3573
Linus Torvalds1da177e2005-04-16 15:20:36 -07003574 rhash_entries= [KNL,NET]
3575 Set number of hash buckets for route cache
3576
Grzegorz Andrejczuke16fd002017-01-20 14:22:36 +01003577 ring3mwait=disable
3578 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
3579 CPUs.
3580
Linus Torvalds1da177e2005-04-16 15:20:36 -07003581 ro [KNL] Mount root device read-only on boot
3582
Kees Cookd2aa1ac2016-02-17 14:41:13 -08003583 rodata= [KNL]
3584 on Mark read-only kernel memory as read-only (default).
3585 off Leave read-only kernel memory writable for debugging.
3586
Heiko Stuebner605df8a2016-02-22 12:55:01 +01003587 rockchip.usb_uart
3588 Enable the uart passthrough on the designated usb port
3589 on Rockchip SoCs. When active, the signals of the
3590 debug-uart get routed to the D+ and D- pins of the usb
3591 port and the regular usb controller gets disabled.
3592
Linus Torvalds1da177e2005-04-16 15:20:36 -07003593 root= [KNL] Root filesystem
Will Drewryf2d34fd2011-08-03 16:21:08 -07003594 See name_to_dev_t comment in init/do_mounts.c.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003595
3596 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3597 mount the root filesystem
3598
3599 rootflags= [KNL] Set root filesystem mount option string
3600
3601 rootfstype= [KNL] Set root filesystem type
3602
Pierre Ossmancc1ed752007-07-15 23:40:35 -07003603 rootwait [KNL] Wait (indefinitely) for root device to show up.
3604 Useful for devices that are detected asynchronously
3605 (e.g. USB and MMC devices).
3606
Robert Tivy5c71d612013-03-28 18:41:46 -07003607 rproc_mem=nn[KMG][@address]
3608 [KNL,ARM,CMA] Remoteproc physical memory block.
3609 Memory area to be used by remote processor image,
3610 managed by CMA.
3611
Linus Torvalds1da177e2005-04-16 15:20:36 -07003612 rw [KNL] Mount root device read-write on boot
3613
3614 S [KNL] Run init in single mode
3615
Gerald Schaeferc60d1ae2014-07-18 17:37:08 +02003616 s390_iommu= [HW,S390]
3617 Set s390 IOTLB flushing mode
3618 strict
3619 With strict flushing every unmap operation will result in
3620 an IOTLB flush. Default is lazy flushing before reuse,
3621 which is faster.
3622
Linus Torvalds1da177e2005-04-16 15:20:36 -07003623 sa1100ir [NET]
3624 See drivers/net/irda/sa1100_ir.c.
3625
Linus Torvalds1da177e2005-04-16 15:20:36 -07003626 sbni= [NET] Granch SBNI12 leased line adapter
Randy Dunlapa9913042005-10-23 12:57:11 -07003627
Mike Travisf6630112009-11-17 18:22:15 -06003628 sched_debug [KNL] Enables verbose scheduler debug messages.
3629
Mel Gormancb251762016-02-05 09:08:36 +00003630 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3631 Allowed values are enable and disable. This feature
3632 incurs a small amount of overhead in the scheduler
3633 but is useful for debugging and performance tuning.
3634
Mike Galbraith5307c952012-05-08 12:20:58 +02003635 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3636 xtime_lock contention on larger systems, and/or RCU lock
3637 contention on all systems with CONFIG_MAXSMP set.
3638 Format: { "0" | "1" }
3639 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3640 1 -- enable.
3641 Note: increases power consumption, thus should only be
3642 enabled if running jitter sensitive (HPC/RT) workloads.
3643
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07003644 security= [SECURITY] Choose a security module to enable at boot.
3645 If this boot parameter is not specified, only the first
3646 security module asking for security registration will be
3647 loaded. An invalid security module name will be treated
3648 as if no module has been chosen.
3649
3650 selinux= [SELINUX] Disable or enable SELinux at boot time.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003651 Format: { "0" | "1" }
3652 See security/selinux/Kconfig help text.
3653 0 -- disable.
3654 1 -- enable.
3655 Default value is set via kernel config option.
3656 If enabled at boot time, /selinux/disable can be used
3657 later to disable prior to initial policy load.
3658
John Johansenc1c124e2010-07-29 14:48:09 -07003659 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3660 Format: { "0" | "1" }
3661 See security/apparmor/Kconfig help text
3662 0 -- disable.
3663 1 -- enable.
3664 Default value is set via kernel config option.
3665
Alan Coxcd4f0ef2007-07-31 00:37:59 -07003666 serialnumber [BUGS=X86-32]
Linus Torvalds1da177e2005-04-16 15:20:36 -07003667
Linus Torvalds1da177e2005-04-16 15:20:36 -07003668 shapers= [NET]
3669 Maximal number of shapers.
Randy Dunlapa9913042005-10-23 12:57:11 -07003670
Linus Torvalds1da177e2005-04-16 15:20:36 -07003671 simeth= [IA-64]
3672 simscsi=
Randy Dunlapa9913042005-10-23 12:57:11 -07003673
Linus Torvalds1da177e2005-04-16 15:20:36 -07003674 slram= [HW,MTD]
3675
Joonsoo Kim423c9292014-10-09 15:26:22 -07003676 slab_nomerge [MM]
3677 Disable merging of slabs with similar size. May be
3678 necessary if there is some reason to distinguish
3679 allocs to different slabs. Debug options disable
3680 merging on their own.
3681 For more information see Documentation/vm/slub.txt.
3682
David Rientjes3df1ccc2011-10-18 22:09:28 -07003683 slab_max_order= [MM, SLAB]
3684 Determines the maximum allowed order for slabs.
3685 A high setting may cause OOMs due to memory
3686 fragmentation. Defaults to 1 for systems with
3687 more than 32MB of RAM, 0 otherwise.
3688
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003689 slub_debug[=options[,slabs]] [MM, SLUB]
3690 Enabling slub_debug allows one to determine the
3691 culprit if slab objects become corrupted. Enabling
3692 slub_debug can create guard zones around objects and
3693 may poison objects when not in use. Also tracks the
3694 last alloc / free. For more information see
3695 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003696
3697 slub_max_order= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003698 Determines the maximum allowed order for slabs.
3699 A high setting may cause OOMs due to memory
3700 fragmentation. For more information see
3701 Documentation/vm/slub.txt.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003702
3703 slub_min_objects= [MM, SLUB]
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003704 The minimum number of objects per slab. SLUB will
3705 increase the slab order up to slub_max_order to
3706 generate a sufficiently large slab able to contain
3707 the number of objects indicated. The higher the number
3708 of objects the smaller the overhead of tracking slabs
3709 and the less frequently locks need to be acquired.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003710 For more information see Documentation/vm/slub.txt.
3711
3712 slub_min_order= [MM, SLUB]
Masanari Iida24775d62012-02-15 00:26:42 +09003713 Determines the minimum page order for slabs. Must be
Christoph Lameterf0630ff2007-07-15 23:38:14 -07003714 lower than slub_max_order.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003715 For more information see Documentation/vm/slub.txt.
3716
3717 slub_nomerge [MM, SLUB]
Joonsoo Kim423c9292014-10-09 15:26:22 -07003718 Same with slab_nomerge. This is supported for legacy.
3719 See slab_nomerge for more information.
Christoph Lameterc1aee212007-05-31 00:40:47 -07003720
Linus Torvalds1da177e2005-04-16 15:20:36 -07003721 smart2= [HW]
3722 Format: <io1>[,<io2>[,...,<io8>]]
3723
Bjorn Helgaasd0d4f692007-05-08 00:36:05 -07003724 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3725 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3726 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3727 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3728 smsc-ircc2.ircc_irq= [HW] IRQ line
3729 smsc-ircc2.ircc_dma= [HW] DMA channel
3730 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3731 0: Toshiba Satellite 1800 (GP data pin select)
3732 1: Fast pin select (default)
3733 2: ATC IRMode
3734
Sascha Silbe52c48c52016-04-05 12:53:38 +02003735 smt [KNL,S390] Set the maximum number of threads (logical
3736 CPUs) to use per physical CPU on systems capable of
3737 symmetric multithreading (SMT). Will be capped to the
3738 actual hardware limit.
3739 Format: <integer>
3740 Default: -1 (no limit)
3741
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003742 softlockup_panic=
3743 [KNL] Should the soft-lockup detector generate panics.
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07003744 Format: <integer>
Ingo Molnar9c44bc02008-05-12 21:21:04 +02003745
Aaron Tomlined235872014-06-23 13:22:05 -07003746 softlockup_all_cpu_backtrace=
3747 [KNL] Should the soft-lockup detector generate
3748 backtraces on all cpus.
3749 Format: <integer>
3750
Linus Torvalds1da177e2005-04-16 15:20:36 -07003751 sonypi.*= [HW] Sony Programmable I/O Control Device driver
Paul Bolle395cf962011-08-15 02:02:26 +02003752 See Documentation/laptops/sonypi.txt
Linus Torvalds1da177e2005-04-16 15:20:36 -07003753
Linus Torvalds1da177e2005-04-16 15:20:36 -07003754 spia_io_base= [HW,MTD]
3755 spia_fio_base=
3756 spia_pedr=
3757 spia_peddr=
3758
Steven Rostedtf38f1d22008-12-16 23:06:40 -05003759 stacktrace [FTRACE]
3760 Enabled the stack tracer on boot up.
3761
Steven Rostedt762e1202011-12-19 22:01:00 -05003762 stacktrace_filter=[function-list]
3763 [FTRACE] Limit the functions that the stack tracer
3764 will trace at boot up. function-list is a comma separated
3765 list of functions. This list can be changed at run
3766 time by the stack_trace_filter file in the debugfs
3767 tracing directory. Note, this enables stack tracing
3768 and the stacktrace above is not needed.
3769
Linus Torvalds1da177e2005-04-16 15:20:36 -07003770 sti= [PARISC,HW]
3771 Format: <num>
3772 Set the STI (builtin display/keyboard on the HP-PARISC
3773 machines) console (graphic card) which should be used
3774 as the initial boot-console.
3775 See also comment in drivers/video/console/sticore.c.
3776
3777 sti_font= [HW]
3778 See comment in drivers/video/console/sticore.c.
3779
3780 stifb= [HW]
3781 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3782
Trond Myklebustcbf11072009-08-09 15:06:19 -04003783 sunrpc.min_resvport=
3784 sunrpc.max_resvport=
3785 [NFS,SUNRPC]
3786 SunRPC servers often require that client requests
3787 originate from a privileged port (i.e. a port in the
3788 range 0 < portnr < 1024).
3789 An administrator who wishes to reserve some of these
3790 ports for other uses may adjust the range that the
3791 kernel's sunrpc client considers to be privileged
3792 using these two parameters to set the minimum and
3793 maximum port values.
3794
Trond Myklebustff3ac5c2016-06-24 10:55:50 -04003795 sunrpc.svc_rpc_per_connection_limit=
3796 [NFS,SUNRPC]
3797 Limit the number of requests that the server will
3798 process in parallel from a single connection.
3799 The default value is 0 (no limit).
3800
Greg Banks42a7fc42007-03-06 01:42:23 -08003801 sunrpc.pool_mode=
3802 [NFS]
3803 Control how the NFS server code allocates CPUs to
3804 service thread pools. Depending on how many NICs
3805 you have and where their interrupts are bound, this
3806 option will affect which CPUs will do NFS serving.
3807 Note: this parameter cannot be changed while the
3808 NFS server is running.
3809
3810 auto the server chooses an appropriate mode
3811 automatically using heuristics
3812 global a single global pool contains all CPUs
3813 percpu one pool for each CPU
3814 pernode one pool for each NUMA node (equivalent
3815 to global on non-NUMA machines)
3816
Trond Myklebustcbf11072009-08-09 15:06:19 -04003817 sunrpc.tcp_slot_table_entries=
3818 sunrpc.udp_slot_table_entries=
3819 [NFS,SUNRPC]
3820 Sets the upper limit on the number of simultaneous
3821 RPC calls that can be sent from the client to a
3822 server. Increasing these values may allow you to
3823 improve throughput, but will also increase the
3824 amount of memory reserved for use by the client.
3825
Brian Norris1d4a9c12015-02-22 21:16:49 -08003826 suspend.pm_test_delay=
3827 [SUSPEND]
3828 Sets the number of seconds to remain in a suspend test
3829 mode before resuming the system (see
3830 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3831 is set. Default value is 5.
3832
Michal Hocko07555ac2013-08-22 16:35:46 -07003833 swapaccount=[0|1]
Michal Hockoa42c3902010-11-24 12:57:08 -08003834 [KNL] Enable accounting of swap in memory resource
3835 controller if no parameter or 1 is given or disable
seokhoon.yoon09c3bcc2016-08-02 23:23:57 +09003836 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
Michal Hockoa42c3902010-11-24 12:57:08 -08003837
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003838 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
Geert Uytterhoevenfff5d992016-12-16 14:28:42 +01003839 Format: { <int> | force | noforce }
Jiri Kosina91fec0f2013-11-27 13:48:09 +01003840 <int> -- Number of I/O TLB slabs
3841 force -- force using of bounce buffers even if they
3842 wouldn't be automatically used by the kernel
Geert Uytterhoevenfff5d992016-12-16 14:28:42 +01003843 noforce -- Never use bounce buffers (for debugging)
Randy Dunlapa9913042005-10-23 12:57:11 -07003844
Linus Torvalds1da177e2005-04-16 15:20:36 -07003845 switches= [HW,M68k]
3846
Andi Kleene52eec12010-09-08 16:54:17 +02003847 sysfs.deprecated=0|1 [KNL]
3848 Enable/disable old style sysfs layout for old udev
3849 on older distributions. When this option is enabled
3850 very new udev will not work anymore. When this option
3851 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3852 in older udev will not work anymore.
3853 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3854 the kernel configuration.
3855
Ingo Molnar5d6f6472006-12-13 00:34:36 -08003856 sysrq_always_enabled
3857 [KNL]
3858 Ignore sysrq setting - this boot parameter will
3859 neutralize any effect of /proc/sys/kernel/sysrq.
3860 Useful for debugging.
3861
Fabian Frederick747029a2014-11-06 19:46:50 +01003862 tcpmhash_entries= [KNL,NET]
3863 Set the number of tcp_metrics_hash slots.
3864 Default value is 8192 or 16384 depending on total
3865 ram pages. This is used to specify the TCP metrics
3866 cache size. See Documentation/networking/ip-sysctl.txt
3867 "tcp_no_metrics_save" section for more details.
3868
Linus Torvalds1da177e2005-04-16 15:20:36 -07003869 tdfx= [HW,DRM]
3870
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003871 test_suspend= [SUSPEND][,N]
David Brownell77437fd2008-07-23 21:28:33 -07003872 Specify "mem" (for Suspend-to-RAM) or "standby" (for
Srinivas Pandruvadaacc82342014-09-02 11:54:41 -07003873 standby suspend) or "freeze" (for suspend type freeze)
3874 as the system sleep state during system startup with
3875 the optional capability to repeat N number of times.
3876 The system is woken from this state using a
3877 wakeup-capable RTC alarm.
David Brownell77437fd2008-07-23 21:28:33 -07003878
Linus Torvalds1da177e2005-04-16 15:20:36 -07003879 thash_entries= [KNL,NET]
3880 Set number of hash buckets for TCP connection
3881
Len Brownf8707ec2007-08-12 00:12:54 -04003882 thermal.act= [HW,ACPI]
3883 -1: disable all active trip points in all thermal zones
3884 <degrees C>: override all lowest active trip points
3885
Len Brownc52a7412007-08-14 15:49:32 -04003886 thermal.crt= [HW,ACPI]
3887 -1: disable all critical trip points in all thermal zones
Zhang Rui22a94d72008-10-17 02:41:20 -04003888 <degrees C>: override all critical trip points
Len Brownc52a7412007-08-14 15:49:32 -04003889
Len Brownf5487142007-08-12 00:12:44 -04003890 thermal.nocrt= [HW,ACPI]
3891 Set to disable actions on ACPI thermal zone
3892 critical and hot trip points.
3893
Len Brown72b33ef2007-08-12 00:12:17 -04003894 thermal.off= [HW,ACPI]
3895 1: disable ACPI thermal control
3896
Len Browna70cdc52007-08-12 00:12:35 -04003897 thermal.psv= [HW,ACPI]
3898 -1: disable all passive trip points
Randy Dunlapada9cfd2008-12-19 10:57:32 -08003899 <degrees C>: override all passive trip points to this
3900 value
Len Browna70cdc52007-08-12 00:12:35 -04003901
Len Brown730ff342007-08-12 00:12:26 -04003902 thermal.tzp= [HW,ACPI]
3903 Specify global default ACPI thermal zone polling rate
3904 <deci-seconds>: poll all this frequency
3905 0: no polling (default)
3906
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003907 threadirqs [KNL]
3908 Force threading of all interrupt handlers except those
Masanari Iida24775d62012-02-15 00:26:42 +09003909 marked explicitly IRQF_NO_THREAD.
Thomas Gleixner8d32a302011-02-23 23:52:23 +00003910
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003911 tmem [KNL,XEN]
3912 Enable the Transcendent memory driver if built-in.
3913
3914 tmem.cleancache=0|1 [KNL, XEN]
3915 Default is on (1). Disable the usage of the cleancache
3916 API to send anonymous pages to the hypervisor.
3917
3918 tmem.frontswap=0|1 [KNL, XEN]
3919 Default is on (1). Disable the usage of the frontswap
Konrad Rzeszutek Wilk37d46e12013-05-14 13:56:42 -04003920 API to send swap pages to the hypervisor. If disabled
3921 the selfballooning and selfshrinking are force disabled.
Konrad Rzeszutek Wilk2ca62b02013-05-08 17:12:44 -04003922
3923 tmem.selfballooning=0|1 [KNL, XEN]
3924 Default is on (1). Disable the driving of swap pages
3925 to the hypervisor.
3926
3927 tmem.selfshrinking=0|1 [KNL, XEN]
3928 Default is on (1). Partial swapoff that immediately
3929 transfers pages from Xen hypervisor back to the
3930 kernel based on different criteria.
3931
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003932 topology= [S390]
3933 Format: {off | on}
3934 Specify if the kernel should make use of the cpu
Sylvestre Ledruf65e51d2011-04-04 15:04:46 -07003935 topology information if the hardware supports this.
3936 The scheduler will make use of this information and
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003937 e.g. base its process migration decisions on it.
Heiko Carstensc9af3fa2010-10-25 16:10:43 +02003938 Default is on.
Heiko Carstens2b1a61f2008-12-25 13:39:23 +01003939
Nishanth Aravamudan2d73bae2014-10-10 09:04:49 -07003940 topology_updates= [KNL, PPC, NUMA]
3941 Format: {off}
3942 Specify if the kernel should ignore (off)
3943 topology updates sent by the hypervisor to this
3944 LPAR.
3945
Linus Torvalds1da177e2005-04-16 15:20:36 -07003946 tp720= [HW,PS2]
3947
Rajiv Andrade225a9be2010-03-25 00:55:32 -03003948 tpm_suspend_pcr=[HW,TPM]
3949 Format: integer pcr id
3950 Specify that at suspend time, the tpm driver
3951 should extend the specified pcr with zeros,
3952 as a workaround for some chips which fail to
3953 flush the last written pcr on TPM_SaveState.
3954 This will guarantee that all the other pcrs
3955 are saved.
3956
Li Zefan9d612be2009-06-24 17:33:15 +08003957 trace_buf_size=nn[KMG]
Joonsoo Kim3e6fb8e2014-12-03 10:39:20 +09003958 [FTRACE] will set tracing buffer size on each cpu.
KOSAKI Motohiro631595f2009-03-10 13:57:10 +09003959
Li Zefan020e5f82009-07-01 10:47:05 +08003960 trace_event=[event-list]
3961 [FTRACE] Set and start specified trace events in order
Brian Norrisd81749e2016-05-23 13:37:58 -07003962 to facilitate early boot debugging. The event-list is a
3963 comma separated list of trace events to enable. See
3964 also Documentation/trace/events.txt
Li Zefan020e5f82009-07-01 10:47:05 +08003965
Steven Rostedt7bcfaf52012-11-01 22:56:07 -04003966 trace_options=[option-list]
3967 [FTRACE] Enable or disable tracer options at boot.
3968 The option-list is a comma delimited list of options
3969 that can be enabled or disabled just as if you were
3970 to echo the option name into
3971
3972 /sys/kernel/debug/tracing/trace_options
3973
3974 For example, to enable stacktrace option (to dump the
3975 stack trace of each event), add to the command line:
3976
3977 trace_options=stacktrace
3978
3979 See also Documentation/trace/ftrace.txt "trace options"
3980 section.
3981
Steven Rostedt (Red Hat)0daa23022014-12-12 22:27:10 -05003982 tp_printk[FTRACE]
3983 Have the tracepoints sent to printk as well as the
3984 tracing ring buffer. This is useful for early boot up
3985 where the system hangs or reboots and does not give the
3986 option for reading the tracing buffer or performing a
3987 ftrace_dump_on_oops.
3988
3989 To turn off having tracepoints sent to printk,
3990 echo 0 > /proc/sys/kernel/tracepoint_printk
3991 Note, echoing 1 into this file without the
3992 tracepoint_printk kernel cmdline option has no effect.
3993
3994 ** CAUTION **
3995
3996 Having tracepoints sent to printk() and activating high
3997 frequency tracepoints such as irq or sched, can cause
3998 the system to live lock.
3999
Steven Rostedt (Red Hat)de7edd32013-06-14 16:21:43 -04004000 traceoff_on_warning
4001 [FTRACE] enable this option to disable tracing when a
4002 warning is hit. This turns off "tracing_on". Tracing can
4003 be enabled again by echoing '1' into the "tracing_on"
4004 file located in /sys/kernel/debug/tracing/
4005
4006 This option is useful, as it disables the trace before
4007 the WARNING dump is called, which prevents the trace to
4008 be filled with content caused by the warning output.
4009
4010 This option can also be set at run time via the sysctl
4011 option: kernel/traceoff_on_warning
4012
Jiri Kosinafcf4d822012-03-21 16:34:02 -07004013 transparent_hugepage=
4014 [KNL]
4015 Format: [always|madvise|never]
4016 Can be used to control the default behavior of the system
4017 with respect to transparent hugepages.
4018 See Documentation/vm/transhuge.txt for more details.
4019
john stultzd3b8f882009-08-17 16:40:47 -07004020 tsc= Disable clocksource stability checks for TSC.
Alok Kataria395628e2008-10-24 17:22:01 -07004021 Format: <string>
4022 [x86] reliable: mark tsc clocksource as reliable, this
john stultzd3b8f882009-08-17 16:40:47 -07004023 disables clocksource verification at runtime, as well
4024 as the stability checks done at bootup. Used to enable
4025 high-resolution timer mode on older hardware, and in
4026 virtualized environment.
Venkatesh Pallipadie82b8e42010-10-04 17:03:20 -07004027 [x86] noirqtime: Do not use TSC to do irq accounting.
4028 Used to run time disable IRQ_TIME_ACCOUNTING on any
4029 platforms where RDTSC is slow and this accounting
4030 can add overhead.
Alok Kataria395628e2008-10-24 17:22:01 -07004031
Randy Dunlapa9913042005-10-23 12:57:11 -07004032 turbografx.map[2|3]= [HW,JOY]
4033 TurboGraFX parallel port interface
4034 Format:
4035 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004036 See also Documentation/input/joystick-parport.txt
4037
Christian Kujaub6935f82011-05-31 15:22:05 +00004038 udbg-immortal [PPC] When debugging early kernel crashes that
Jani Nikulae52347b2016-11-03 12:10:10 +02004039 happen after console_init() and before a proper
Christian Kujaub6935f82011-05-31 15:22:05 +00004040 console driver takes over, this boot options might
4041 help "seeing" what's going on.
4042
Eric Dumazetf86dcc52009-10-07 00:37:59 +00004043 uhash_entries= [KNL,NET]
4044 Set number of hash buckets for UDP/UDP-Lite connections
4045
Alan Stern5f8364b2006-12-05 16:29:55 -05004046 uhci-hcd.ignore_oc=
4047 [USB] Ignore overcurrent events (default N).
4048 Some badly-designed motherboards generate lots of
4049 bogus events, for ports that aren't wired to
4050 anything. Set this parameter to avoid log spamming.
4051 Note that genuine overcurrent events won't be
4052 reported either.
4053
Simon Arlotte3a61b02008-07-19 23:32:54 +01004054 unknown_nmi_panic
Randy Dunlap44a4dcf2011-04-04 15:02:24 -07004055 [X86] Cause panic on unknown NMI.
Simon Arlotte3a61b02008-07-19 23:32:54 +01004056
Carl-Daniel Hailfingerc4fc2342011-05-31 21:31:08 +02004057 usbcore.authorized_default=
4058 [USB] Default USB device authorization:
4059 (default -1 = authorized except for wireless USB,
4060 0 = not authorized, 1 = authorized)
4061
Alan Sternb5e795f2007-02-20 15:00:53 -05004062 usbcore.autosuspend=
4063 [USB] The autosuspend time delay (in seconds) used
4064 for newly-detected USB devices (default 2). This
4065 is the time required before an idle device will be
4066 autosuspended. Devices for which the delay is set
Alan Sterneaafbc32007-03-13 16:39:15 -04004067 to a negative value won't be autosuspended at all.
Alan Sternb5e795f2007-02-20 15:00:53 -05004068
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004069 usbcore.usbfs_snoop=
4070 [USB] Set to log all usbfs traffic (default 0 = off).
4071
Alan Stern0290cc92015-11-20 13:53:22 -05004072 usbcore.usbfs_snoop_max=
4073 [USB] Maximum number of bytes to snoop in each URB
4074 (default = 65536).
4075
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004076 usbcore.blinkenlights=
4077 [USB] Set to cycle leds on hubs (default 0 = off).
4078
4079 usbcore.old_scheme_first=
4080 [USB] Start with the old device initialization
4081 scheme (default 0 = off).
4082
Alan Stern3f5eb8d2011-11-17 16:41:35 -05004083 usbcore.usbfs_memory_mb=
4084 [USB] Memory limit (in MB) for buffers allocated by
4085 usbfs (default = 16, 0 = max = 2047).
4086
Jaroslav Kyselafd7c5192008-10-10 16:24:45 +02004087 usbcore.use_both_schemes=
4088 [USB] Try the other device initialization scheme
4089 if the first one fails (default 1 = enabled).
4090
4091 usbcore.initial_descriptor_timeout=
4092 [USB] Specifies timeout for the initial 64-byte
4093 USB_REQ_GET_DESCRIPTOR request in milliseconds
4094 (default 5000 = 5.0 seconds).
4095
Oliver Neukum40d58142015-12-03 15:03:32 +01004096 usbcore.nousb [USB] Disable the USB subsystem
4097
Linus Torvalds1da177e2005-04-16 15:20:36 -07004098 usbhid.mousepoll=
4099 [USBHID] The interval which mice are to be polled at.
Randy Dunlapa9913042005-10-23 12:57:11 -07004100
Alan Sternd4f373e2008-11-10 14:07:45 -05004101 usb-storage.delay_use=
4102 [UMS] The delay in seconds before a new device is
Mark Knibbs19101952014-11-04 13:00:15 +00004103 scanned for Logical Units (default 1).
Alan Sternd4f373e2008-11-10 14:07:45 -05004104
4105 usb-storage.quirks=
4106 [UMS] A list of quirks entries to supplement or
4107 override the built-in unusual_devs list. List
4108 entries are separated by commas. Each entry has
4109 the form VID:PID:Flags where VID and PID are Vendor
4110 and Product ID values (4-digit hex numbers) and
4111 Flags is a set of characters, each corresponding
4112 to a common usb-storage quirk flag as follows:
Alan Sternc838ea42008-12-15 10:40:06 -05004113 a = SANE_SENSE (collect more than 18 bytes
4114 of sense data);
Alan Sterna0bb1082009-12-07 16:39:16 -05004115 b = BAD_SENSE (don't collect more than 18
4116 bytes of sense data);
Alan Sternd4f373e2008-11-10 14:07:45 -05004117 c = FIX_CAPACITY (decrease the reported
4118 device capacity by one sector);
Karl Relton51169012011-05-18 21:42:34 +01004119 d = NO_READ_DISC_INFO (don't use
4120 READ_DISC_INFO command);
4121 e = NO_READ_CAPACITY_16 (don't use
4122 READ_CAPACITY_16 command);
Hans de Goede734016b2014-09-16 18:36:52 +02004123 f = NO_REPORT_OPCODES (don't use report opcodes
4124 command, uas only);
Hans de Goedeee136af2015-04-21 11:20:31 +02004125 g = MAX_SECTORS_240 (don't transfer more than
4126 240 sectors at a time, uas only);
Alan Sternc838ea42008-12-15 10:40:06 -05004127 h = CAPACITY_HEURISTICS (decrease the
4128 reported device capacity by one
4129 sector if the number is odd);
Alan Sternd4f373e2008-11-10 14:07:45 -05004130 i = IGNORE_DEVICE (don't bind to this
4131 device);
Hans de Goede13630742016-04-12 12:27:09 +02004132 j = NO_REPORT_LUNS (don't use report luns
4133 command, uas only);
Alan Sternd4f373e2008-11-10 14:07:45 -05004134 l = NOT_LOCKABLE (don't try to lock and
4135 unlock ejectable media);
4136 m = MAX_SECTORS_64 (don't transfer more
4137 than 64 sectors = 32 KB at a time);
Alan Stern21c13a42011-06-07 11:35:52 -04004138 n = INITIAL_READ10 (force a retry of the
4139 initial READ(10) command);
Alan Sternc838ea42008-12-15 10:40:06 -05004140 o = CAPACITY_OK (accept the capacity
4141 reported by the device);
Namjae Jeoneaa05df2012-07-07 23:05:28 -04004142 p = WRITE_CACHE (the device cache is ON
4143 by default);
Alan Sternd4f373e2008-11-10 14:07:45 -05004144 r = IGNORE_RESIDUE (the device reports
4145 bogus residue values);
4146 s = SINGLE_LUN (the device has only one
4147 Logical Unit);
Hans de Goede59307852014-09-15 16:04:12 +02004148 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4149 commands, uas only);
Alan Sternb6089f12014-09-02 15:42:18 -04004150 u = IGNORE_UAS (don't bind to the uas driver);
Alan Sternd4f373e2008-11-10 14:07:45 -05004151 w = NO_WP_DETECT (don't test whether the
4152 medium is write-protected).
Oliver Neukum050bc4e2016-09-12 15:19:41 +02004153 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4154 even if the device claims no cache)
Alan Sternd4f373e2008-11-10 14:07:45 -05004155 Example: quirks=0419:aaf5:rl,0421:0433:rc
4156
Stephen Boydac1667d2011-08-13 12:34:50 -07004157 user_debug= [KNL,ARM]
4158 Format: <int>
4159 See arch/arm/Kconfig.debug help text.
4160 1 - undefined instruction events
4161 2 - system calls
4162 4 - invalid data aborts
4163 8 - SIGSEGV faults
4164 16 - SIGBUS faults
4165 Example: user_debug=31
4166
Ian Campbell14315592010-02-17 10:38:10 +00004167 userpte=
4168 [X86] Flags controlling user PTE allocations.
4169
4170 nohigh = do not allocate PTE pages in
4171 HIGHMEM regardless of setting
4172 of CONFIG_HIGHPTE.
4173
Jaswinder Singh Rajput6cececf2009-04-14 14:03:43 +05304174 vdso= [X86,SH]
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004175 On X86_32, this is an alias for vdso32=. Otherwise:
4176
4177 vdso=1: enable VDSO (the default)
Ingo Molnare6e54942006-06-27 02:53:50 -07004178 vdso=0: disable VDSO mapping
4179
Andy Lutomirskib0b49f22014-03-13 16:01:26 -07004180 vdso32= [X86] Control the 32-bit vDSO
4181 vdso32=1: enable 32-bit VDSO
4182 vdso32=0 or vdso32=2: disable 32-bit VDSO
4183
4184 See the help text for CONFIG_COMPAT_VDSO for more
4185 details. If CONFIG_COMPAT_VDSO is set, the default is
4186 vdso32=0; otherwise, the default is vdso32=1.
4187
4188 For compatibility with older kernels, vdso32=2 is an
4189 alias for vdso32=0.
4190
4191 Try vdso32=0 if you encounter an error that says:
4192 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
Roland McGrathaf65d642008-01-30 13:30:43 +01004193
Yasuaki Ishimatsud080d392007-07-17 21:22:55 +09004194 vector= [IA-64,SMP]
4195 vector=percpu: enable percpu vector domain
4196
Linus Torvalds1da177e2005-04-16 15:20:36 -07004197 video= [FB] Frame buffer configuration
4198 See Documentation/fb/modedb.txt.
4199
Aaron Lu3afe6da2013-06-20 15:08:55 +08004200 video.brightness_switch_enabled= [0,1]
4201 If set to 1, on receiving an ACPI notify event
4202 generated by hotkey, video driver will adjust brightness
4203 level and then send out the event to user space through
4204 the allocated input device; If set to 0, video driver
4205 will only send out the event without touching backlight
4206 brightness level.
Rafael J. Wysocki28437682014-07-14 19:35:45 +02004207 default: 1
Aaron Lu3afe6da2013-06-20 15:08:55 +08004208
Pawel Moll81a054c2012-05-09 18:30:16 +01004209 virtio_mmio.device=
4210 [VMMIO] Memory mapped virtio (platform) device.
4211
4212 <size>@<baseaddr>:<irq>[:<id>]
4213 where:
4214 <size> := size (can use standard suffixes
4215 like K, M and G)
4216 <baseaddr> := physical base address
4217 <irq> := interrupt number (as passed to
4218 request_irq())
4219 <id> := (optional) platform device id
4220 example:
4221 virtio_mmio.device=1K@0x100b0000:48:7
4222
4223 Can be used multiple times for multiple devices.
4224
Alan Coxcd4f0ef2007-07-31 00:37:59 -07004225 vga= [BOOT,X86-32] Select a particular video mode
Kyle McMartin954a8b82009-02-19 16:48:14 -05004226 See Documentation/x86/boot.txt and
Randy Dunlapa9913042005-10-23 12:57:11 -07004227 Documentation/svga.txt.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004228 Use vga=ask for menu.
4229 This is actually a boot loader parameter; the value is
4230 passed to the kernel using a special protocol.
4231
Randy Dunlapa9913042005-10-23 12:57:11 -07004232 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
Linus Torvalds1da177e2005-04-16 15:20:36 -07004233 size of <nn>. This can be used to increase the
4234 minimum size (128MB on x86). It can also be used to
4235 decrease the size and leave more room for directly
4236 mapped kernel RAM.
4237
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004238 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4239 Format: <command>
Linus Torvalds1da177e2005-04-16 15:20:36 -07004240
Peter Oberparleiter585c3042006-06-29 15:08:25 +02004241 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4242 Format: <command>
4243
4244 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4245 Format: <command>
Randy Dunlapa9913042005-10-23 12:57:11 -07004246
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004247 vsyscall= [X86-64]
4248 Controls the behavior of vsyscalls (i.e. calls to
4249 fixed addresses of 0xffffffffff600x00 from legacy
4250 code). Most statically-linked binaries and older
4251 versions of glibc use these calls. Because these
4252 functions are at fixed addresses, they make nice
4253 targets for exploits that can control RIP.
4254
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004255 emulate [default] Vsyscalls turn into traps and are
4256 emulated reasonably safely.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004257
Andy Lutomirski2e57ae02011-11-07 16:33:41 -08004258 native Vsyscalls are native syscall instructions.
Andy Lutomirski3ae36652011-08-10 11:15:32 -04004259 This is a little bit faster than trapping
4260 and makes a few dynamic recompilers work
4261 better than they would in emulation mode.
4262 It also makes exploits much easier to write.
4263
4264 none Vsyscalls don't work at all. This makes
4265 them quite hard to use for exploits but
4266 might break your system.
4267
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004268 vt.color= [VT] Default text color.
4269 Format: 0xYX, X = foreground, Y = background.
4270 Default: 0x07 = light gray on black.
4271
Clemens Ladisch9ea9a882009-12-15 16:45:39 -08004272 vt.cur_default= [VT] Default cursor shape.
4273 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4274 the parameters of the <Esc>[?A;B;Cc escape sequence;
4275 see VGA-softcursor.txt. Default: 2 = underline.
4276
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004277 vt.default_blu= [VT]
4278 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4279 Change the default blue palette of the console.
4280 This is a 16-member array composed of values
4281 ranging from 0-255.
4282
4283 vt.default_grn= [VT]
4284 Format: <green0>,<green1>,<green2>,...,<green15>
4285 Change the default green palette of the console.
4286 This is a 16-member array composed of values
4287 ranging from 0-255.
4288
4289 vt.default_red= [VT]
4290 Format: <red0>,<red1>,<red2>,...,<red15>
4291 Change the default red palette of the console.
4292 This is a 16-member array composed of values
4293 ranging from 0-255.
4294
4295 vt.default_utf8=
4296 [VT]
4297 Format=<0|1>
4298 Set system-wide default UTF-8 mode for all tty's.
4299 Default is 1, i.e. UTF-8 mode is enabled for all
4300 newly opened terminals.
4301
Matthew Garrettf6c06b62009-11-13 15:14:11 -05004302 vt.global_cursor_default=
4303 [VT]
4304 Format=<-1|0|1>
4305 Set system-wide default for whether a cursor
4306 is shown on new VTs. Default is -1,
4307 i.e. cursors will be created by default unless
4308 overridden by individual drivers. 0 will hide
4309 cursors, 1 will display them.
4310
Clemens Ladisch3855ae12013-08-04 13:09:50 +02004311 vt.italic= [VT] Default color for italic text; 0-15.
4312 Default: 2 = green.
4313
4314 vt.underline= [VT] Default color for underlined text; 0-15.
4315 Default: 3 = cyan.
4316
Randy Dunlap4724ba572010-05-03 11:42:52 -07004317 watchdog timers [HW,WDT] For information on watchdog timers,
4318 see Documentation/watchdog/watchdog-parameters.txt
4319 or other driver-specific files in the
4320 Documentation/watchdog/ directory.
Linus Torvalds1da177e2005-04-16 15:20:36 -07004321
Tejun Heo82607adc2015-12-08 11:28:04 -05004322 workqueue.watchdog_thresh=
4323 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4324 warn stall conditions and dump internal state to
4325 help debugging. 0 disables workqueue stall
4326 detection; otherwise, it's the stall threshold
4327 duration in seconds. The default value is 30 and
4328 it can be updated at runtime by writing to the
4329 corresponding sysfs file.
4330
Tejun Heod55262c2013-04-01 11:23:38 -07004331 workqueue.disable_numa
4332 By default, all work items queued to unbound
4333 workqueues are affine to the NUMA nodes they're
4334 issued on, which results in better behavior in
4335 general. If NUMA affinity needs to be disabled for
4336 whatever reason, this option can be used. Note
4337 that this also can be controlled per-workqueue for
4338 workqueues visible under /sys/bus/workqueue/.
4339
Viresh Kumarcee22a12013-04-08 16:45:40 +05304340 workqueue.power_efficient
4341 Per-cpu workqueues are generally preferred because
4342 they show better performance thanks to cache
4343 locality; unfortunately, per-cpu workqueues tend to
4344 be more power hungry than unbound workqueues.
4345
4346 Enabling this makes the per-cpu workqueues which
4347 were observed to contribute significantly to power
4348 consumption unbound, leading to measurably lower
4349 power usage at the cost of small performance
4350 overhead.
4351
4352 The default value of this parameter is determined by
4353 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4354
Tejun Heof303fcc2016-02-09 17:59:38 -05004355 workqueue.debug_force_rr_cpu
4356 Workqueue used to implicitly guarantee that work
4357 items queued without explicit CPU specified are put
4358 on the local CPU. This guarantee is no longer true
4359 and while local CPU is still preferred work items
4360 may be put on foreign CPUs. This debug option
4361 forces round-robin CPU selection to flush out
4362 usages which depend on the now broken guarantee.
4363 When enabled, memory and cache locality will be
4364 impacted.
4365
Randy Dunlap0cb55ad2009-04-05 15:55:22 -07004366 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4367 default x2apic cluster mode on platforms
4368 supporting x2apic.
4369
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004370 x86_intel_mid_timer= [X86-32,APBT]
4371 Choose timer option for x86 Intel MID platform.
Jacob Panbb24c472009-09-02 07:37:17 -07004372 Two valid options are apbt timer only and lapic timer
4373 plus one apbt timer for broadcast timer.
Kuppuswamy Sathyanarayanan712b6aa2013-10-17 15:35:29 -07004374 x86_intel_mid_timer=apbt_only | lapic_and_apbt
Jacob Panbb24c472009-09-02 07:37:17 -07004375
Juergen Grossc70727a2015-07-17 06:51:36 +02004376 xen_512gb_limit [KNL,X86-64,XEN]
4377 Restricts the kernel running paravirtualized under Xen
4378 to use only up to 512 GB of RAM. The reason to do so is
4379 crash analysis tools and Xen tools for doing domain
4380 save/restore/migration must be enabled to handle larger
4381 domains.
4382
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004383 xen_emul_unplug= [HW,X86,XEN]
4384 Unplug Xen emulated devices
4385 Format: [unplug0,][unplug1]
4386 ide-disks -- unplug primary master IDE devices
4387 aux-ide-disks -- unplug non-primary-master IDE devices
4388 nics -- unplug network devices
4389 all -- unplug all emulated devices (NICs and IDE disks)
Ian Campbell1dc7ce92010-08-23 11:59:29 +01004390 unnecessary -- unplugging emulated devices is
4391 unnecessary even if the host did not respond to
4392 the unplug protocol
Ian Campbellc93a4df2010-08-23 11:59:28 +01004393 never -- do not unplug even if version check succeeds
Stefano Stabellinic1c54132010-05-14 12:44:30 +01004394
Konrad Rzeszutek Wilk15a3eac2013-09-25 10:07:20 -04004395 xen_nopvspin [X86,XEN]
4396 Disables the ticketlock slowpath using Xen PV
4397 optimizations.
4398
Konrad Rzeszutek Wilk8d693b92014-07-11 11:51:35 -04004399 xen_nopv [X86]
4400 Disables the PV optimizations forcing the HVM guest to
4401 run as generic HVM guest with no PV drivers.
4402
Linus Torvalds1da177e2005-04-16 15:20:36 -07004403 xirc2ps_cs= [NET,PCMCIA]
Randy Dunlapa9913042005-10-23 12:57:11 -07004404 Format:
4405 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]