Commit 20651af9 authored by Yinghai Lu's avatar Yinghai Lu Committed by Ingo Molnar

x86: fix mttr trimming

Pavel Emelyanov reported that his networking card did not work
and bisected it down to:

The commit

  x86_32: trim memory by updating e820

broke my e1000 card: on loading driver says that

  e1000: probe of 0000:04:03.0 failed with error -5

and the interface doesn't appear.

on a 32-bit kernel, base will overflow when try to do PAGE_SHIFT,
and highest_addr will always less 4G.

So use pfn instead of address to avoid the overflow when more than
4g RAM is installed on a 32-bit kernel.

Many thanks to Pavel Emelyanov for reporting and testing it.
Bisected-by: default avatarPavel Emelyanov <>
Signed-off-by: default avatarYinghai Lu <>
Tested-by: default avatarPavel Emelyanov <>
Signed-off-by: default avatarIngo Molnar <>
parent 971a52d6
......@@ -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;
......@@ -682,28 +682,27 @@ int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
mtrr_if->get(i, &base, &size, &type);
if (type != MTRR_TYPE_WRBACK)
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");
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);
" all of memory, losing %luMB of RAM.\n",
(end_pfn - highest_pfn) >> (20 - PAGE_SHIFT));
printk(KERN_INFO "update e820 for mtrr\n");
trim_start = highest_addr;
trim_start = highest_pfn;
trim_start <<= PAGE_SHIFT;
trim_size = end_pfn;
trim_size <<= PAGE_SHIFT;
trim_size -= trim_start;
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