i386: paravirt boot sequence
This patch uses the updated boot protocol to do paravirtualized boot.
If the boot version is >= 2.07, then it will do two things:
1. Check the bootparams loadflags to see if we should reload the
segment registers and clear interrupts. This is appropriate
for normal native boot and some paravirtualized environments, but
inapproprate for others.
2. Check the hardware architecture, and dispatch to the appropriate
kernel entrypoint. If the bootloader doesn't set this, then we
simply do the normal boot sequence.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@in.ibm.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index f35ea22..a0ae2e7 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -27,13 +27,22 @@
#include <asm/segment.h>
#include <asm/page.h>
#include <asm/boot.h>
+#include <asm/asm-offsets.h>
.section ".text.head","ax",@progbits
.globl startup_32
startup_32:
- cld
- cli
+ /* check to see if KEEP_SEGMENTS flag is meaningful */
+ cmpw $0x207, BP_version(%esi)
+ jb 1f
+
+ /* test KEEP_SEGMENTS flag to see if the bootloader is asking
+ * us to not reload segments */
+ testb $(1<<6), BP_loadflags(%esi)
+ jnz 2f
+
+1: cli
movl $(__BOOT_DS),%eax
movl %eax,%ds
movl %eax,%es
@@ -41,6 +50,8 @@
movl %eax,%gs
movl %eax,%ss
+2: cld
+
/* Calculate the delta between where we were compiled to run
* at and where we were actually loaded at. This can only be done
* with a short local call on x86. Nothing else will tell us what