x86_32: trim memory by updating e820
when MTRRs are not covering the whole e820 table, we need to trim the
RAM and need to update e820.
reuse some code on 64-bit as well.
here need to add early_get_cap and use it in early_cpu_detect, and move
mtrr_bp_init early.
The code successfully trimmed the memory map on Justin's system:
from:
[ 0.000000] BIOS-e820: 0000000100000000 - 000000022c000000 (usable)
to:
[ 0.000000] modified: 0000000100000000 - 0000000228000000 (usable)
[ 0.000000] modified: 0000000228000000 - 000000022c000000 (reserved)
According to Justin it makes quite a difference:
| When I boot the box without any trimming it acts like a 286 or 386,
| takes about 10 minutes to boot (using raptor disks).
Signed-off-by: Yinghai Lu <yinghai.lu@sun.com>
Tested-by: Justin Piszcz <jpiszcz@lucidpixels.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/setup_32.c b/arch/x86/kernel/setup_32.c
index 26a56f7..83ba3ca 100644
--- a/arch/x86/kernel/setup_32.c
+++ b/arch/x86/kernel/setup_32.c
@@ -48,6 +48,7 @@
#include <video/edid.h>
+#include <asm/mtrr.h>
#include <asm/apic.h>
#include <asm/e820.h>
#include <asm/mpspec.h>
@@ -758,6 +759,11 @@
max_low_pfn = setup_memory();
+ /* update e820 for memory not covered by WB MTRRs */
+ mtrr_bp_init();
+ if (mtrr_trim_uncached_memory(max_pfn))
+ max_low_pfn = setup_memory();
+
#ifdef CONFIG_VMI
/*
* Must be after max_low_pfn is determined, and before kernel