From 093af8d7f0ba3c6be1485973508584ef081e9f93 Mon Sep 17 00:00:00 2001
From: Yinghai Lu <Yinghai.Lu@Sun.COM>
Date: Wed, 30 Jan 2008 13:33:32 +0100
Subject: 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>
---
 arch/x86/kernel/setup_32.c | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'arch/x86/kernel/setup_32.c')

diff --git a/arch/x86/kernel/setup_32.c b/arch/x86/kernel/setup_32.c
index 26a56f714d34..83ba3ca5f431 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 @@ void __init setup_arch(char **cmdline_p)
 
 	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
-- 
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