Commit 77db9885 authored May 09, 2008 by Venki Pallipadi Committed by Jesse Barnes May 13, 2008

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>

parent 439a7733

arch/x86/pci/i386.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -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);