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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>
This commit is contained in:
Venki Pallipadi 2008-05-09 13:05:19 -07:00 committed by Jesse Barnes
parent 439a7733e8
commit 77db988564
1 changed files with 1 additions and 3 deletions
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4
arch/x86/pci/i386.c
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@ -301,15 +301,13 @@ int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
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);