x86: fix mttr trimming

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

"
The commit

  093af8d7f0ba3c6be1485973508584ef081e9f93
  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: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Yinghai Lu <yinghai.lu@sun.com>
Tested-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 10 deletions

diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 1e27b69a7a0e..b6e136f23d3d 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;
 
@@ -682,28 +682,27 @@ int __init mtrr_trim_uncached_memory(unsigned long end_pfn)
                 mtrr_if->get(i, &base, &size, &type);
                 if (type != MTRR_TYPE_WRBACK)
                         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);
+                        " all of memory, losing %luMB of RAM.\n",
+                        (end_pfn - highest_pfn) >> (20 - PAGE_SHIFT));
 
                 WARN_ON(1);
 
                 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;