x86/PCI: X86_PAT & mprotect
Some versions of X used the mprotect workaround to change caching type from UC
to WB, so that it can then use mtrr to program WC for that region [1]. Change
the mmap of pci space through /sys or /proc interfaces from UC to UC_MINUS.
With this change, X will not need to use mprotect workaround to get WC type
since the MTRR mapping type will be honored.
The bug in mprotect that clobbers PAT bits is fixed in a follow on patch. So,
this X workaround will stop working as well.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c
index 8af0f0b..10fb308 100644
--- a/arch/x86/pci/i386.c
+++ b/arch/x86/pci/i386.c
@@ -301,15 +301,13 @@
prot = pgprot_val(vma->vm_page_prot);
if (pat_wc_enabled && write_combine)
prot |= _PAGE_CACHE_WC;
- else if (pat_wc_enabled)
+ else if (pat_wc_enabled || boot_cpu_data.x86 > 3)
/*
* ioremap() and ioremap_nocache() defaults to UC MINUS for now.
* To avoid attribute conflicts, request UC MINUS here
* aswell.
*/
prot |= _PAGE_CACHE_UC_MINUS;
- else if (boot_cpu_data.x86 > 3)
- prot |= _PAGE_CACHE_UC;
vma->vm_page_prot = __pgprot(prot);