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Subject[PATCH][Regression] x86, 32-bit: trim memory not covered by wb mtrrs - FIX
Date
Hello,

The following commit caused my X server to stop working.

commit 99fc8d424bc5d803fe92cad56c068fe64e73747a
Author: Jesse Barnes <jesse.barnes@intel.com>
Date: Wed Jan 30 13:33:18 2008 +0100

x86, 32-bit: trim memory not covered by wb mtrrs

This patch fixes the improper handling of addresses > 4G by mtrr_trim_uncached_memory.
This, now brings up X on my system.

Signed-off-by: Balaji Rao <balajirrao@gmail.com>

diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 1e27b69..b0f1d48 100644
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -659,7 +659,7 @@ static __init int amd_special_default_mtrr(void)
*/
int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
{
- unsigned long i, base, size, highest_addr = 0, def, dummy;
+ unsigned long i, base, size, highest_pfn = 0, def, dummy;
mtrr_type type;
u64 trim_start, trim_size;

@@ -682,30 +682,27 @@ int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
mtrr_if->get(i, &base, &size, &type);
if (type != MTRR_TYPE_WRBACK)
continue;
- base <<= PAGE_SHIFT;
- size <<= PAGE_SHIFT;
- if (highest_addr < base + size)
- highest_addr = base + size;
+ if (highest_pfn < base + size)
+ highest_pfn = base + size;
}

/* kvm/qemu doesn't have mtrr set right, don't trim them all */
- if (!highest_addr) {
+ if (!highest_pfn) {
printk(KERN_WARNING "WARNING: strange, CPU MTRRs all blank?\n");
WARN_ON(1);
return 0;
}

- if ((highest_addr >> PAGE_SHIFT) < end_pfn) {
+ if (highest_pfn < end_pfn) {
printk(KERN_WARNING "WARNING: BIOS bug: CPU MTRRs don't cover"
" all of memory, losing %LdMB of RAM.\n",
- (((u64)end_pfn << PAGE_SHIFT) - highest_addr) >> 20);
+ ((u64)(end_pfn - highest_pfn) << PAGE_SHIFT) >> 20);

WARN_ON(1);

printk(KERN_INFO "update e820 for mtrr\n");
- trim_start = highest_addr;
- trim_size = end_pfn;
- trim_size <<= PAGE_SHIFT;
+ trim_start = highest_pfn << PAGE_SHIFT;
+ trim_size = end_pfn << PAGE_SHIFT;
trim_size -= trim_start;
add_memory_region(trim_start, trim_size, E820_RESERVED);
update_e820();

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