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authorBjorn Helgaas <bjorn.helgaas@hp.com>2010-12-16 10:39:02 -0700
committerJesse Barnes <jbarnes@virtuousgeek.org>2010-12-17 10:01:30 -0800
commita2c606d53ab71dee6410f10ef0adf67321d60e06 (patch)
tree7a4cf519cbfc01fd1c4273c1481f40f4cd7d00bc
parent4dc2287c1805e7fe8a7cb90bbcd44abee8cdb914 (diff)
x86: avoid high BIOS area when allocating address space
This prevents allocation of the last 2MB before 4GB. The experiment described here shows Windows 7 ignoring the last 1MB: https://bugzilla.kernel.org/show_bug.cgi?id=23542#c27 This patch ignores the top 2MB instead of just 1MB because H. Peter Anvin says "There will be ROM at the top of the 32-bit address space; it's a fact of the architecture, and on at least older systems it was common to have a shadow 1 MiB below." Acked-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
-rw-r--r--arch/x86/include/asm/e820.h3
-rw-r--r--arch/x86/kernel/resource.c3
2 files changed, 5 insertions, 1 deletions
diff --git a/arch/x86/include/asm/e820.h b/arch/x86/include/asm/e820.h
index 5be1542fbfa..e99d55d74df 100644
--- a/arch/x86/include/asm/e820.h
+++ b/arch/x86/include/asm/e820.h
@@ -72,6 +72,9 @@ struct e820map {
#define BIOS_BEGIN 0x000a0000
#define BIOS_END 0x00100000
+#define BIOS_ROM_BASE 0xffe00000
+#define BIOS_ROM_END 0xffffffff
+
#ifdef __KERNEL__
/* see comment in arch/x86/kernel/e820.c */
extern struct e820map e820;
diff --git a/arch/x86/kernel/resource.c b/arch/x86/kernel/resource.c
index 89638af2ff1..2a26819bb6a 100644
--- a/arch/x86/kernel/resource.c
+++ b/arch/x86/kernel/resource.c
@@ -37,10 +37,11 @@ static void remove_e820_regions(struct resource *avail)
void arch_remove_reservations(struct resource *avail)
{
- /* Trim out BIOS area (low 1MB) and E820 regions */
+ /* Trim out BIOS areas (low 1MB and high 2MB) and E820 regions */
if (avail->flags & IORESOURCE_MEM) {
if (avail->start < BIOS_END)
avail->start = BIOS_END;
+ resource_clip(avail, BIOS_ROM_BASE, BIOS_ROM_END);
remove_e820_regions(avail);
}