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authorRavikiran G Thirumalai <kiran@scalex86.org>2008-10-30 16:59:21 -0400
committerIngo Molnar <mingo@elte.hu>2008-10-30 18:54:41 -0400
commit9e41bff2708e420e61e6b89a54c15232857069b1 (patch)
treede662b6e4d8303abae9062e45edb7a481cb6bfb9 /arch/x86/mm
parentee477524b461324ed8fc950f451c3671dc79f12e (diff)
x86: fix /dev/mem mmap breakage when PAT is disabled
Impact: allow /dev/mem mmaps on non-PAT CPUs/platforms Fix mmap to /dev/mem when CONFIG_X86_PAT is off and CONFIG_STRICT_DEVMEM is off mmap to /dev/mem on kernel memory has been failing since the introduction of PAT (CONFIG_STRICT_DEVMEM=n case). Seems like the check to avoid cache aliasing with PAT is kicking in even when PAT is disabled. The bug seems to have crept in 2.6.26. This patch makes sure that the mmap to regular kernel memory succeeds if CONFIG_STRICT_DEVMEM=n and PAT is disabled, and the checks to avoid cache aliasing still happens if PAT is enabled. Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org> Tested-by: Tim Sirianni <tim@scalemp.com> Cc: <stable@kernel.org> Acked-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/mm')
-rw-r--r--arch/x86/mm/pat.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 738fd0f24958..eb1bf000d12e 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -481,12 +481,16 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size)
481 return 1; 481 return 1;
482} 482}
483#else 483#else
484/* This check is needed to avoid cache aliasing when PAT is enabled */
484static inline int range_is_allowed(unsigned long pfn, unsigned long size) 485static inline int range_is_allowed(unsigned long pfn, unsigned long size)
485{ 486{
486 u64 from = ((u64)pfn) << PAGE_SHIFT; 487 u64 from = ((u64)pfn) << PAGE_SHIFT;
487 u64 to = from + size; 488 u64 to = from + size;
488 u64 cursor = from; 489 u64 cursor = from;
489 490
491 if (!pat_enabled)
492 return 1;
493
490 while (cursor < to) { 494 while (cursor < to) {
491 if (!devmem_is_allowed(pfn)) { 495 if (!devmem_is_allowed(pfn)) {
492 printk(KERN_INFO 496 printk(KERN_INFO