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| author | Suresh Siddha <suresh.b.siddha@intel.com> | 2009-10-26 13:21:32 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-01-25 10:49:41 -0800 |
| commit | 538a6fdbcffffe7ddecf13f94129502524f771d5 (patch) | |
| tree | 6bfc656c46dad117fbda1516135c741b9b1f4164 | |
| parent | e0f5cfa7c18b411634e73923841eccd3a4c0ce7f (diff) | |
| download | lwn-538a6fdbcffffe7ddecf13f94129502524f771d5.tar.gz lwn-538a6fdbcffffe7ddecf13f94129502524f771d5.zip | |
x86/PCI/PAT: return EINVAL for pci mmap WC request for !pat_enabled
commit 2992e545ea006992ec9dc91c4fa996ce1e15f921 upstream.
Thomas Schlichter reported:
> X.org uses libpciaccess which tries to mmap with write combining enabled via
> /sys/bus/pci/devices/*/resource0_wc. Currently, when PAT is not enabled, the
> kernel does fall back to uncached mmap. Then libpciaccess thinks it succeeded
> mapping with write combining enabled and does not set up suited MTRR entries.
> ;-(
Instead of silently mapping pci mmap region as UC minus in the case
of !pat_enabled and wc request, we can return error. Eric Anholt mentioned
that caller (like X) typically follows up with UC minus pci mmap request and
if there is a free mtrr slot, caller will manage adding WC mtrr.
Jesse Barnes says:
> Older versions of libpciaccess will behave better if we do it that way
> (iirc it only allocates an MTRR if the resource_wc file doesn't exist or
> fails to get mapped).
Reported-by: Thomas Schlichter <thomas.schlichter@web.de>
Signed-off-by: Thomas Schlichter <thomas.schlichter@web.de>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Acked-by: Eric Anholt <eric@anholt.net>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | arch/x86/pci/i386.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c index b22d13b0c71d..a672f12afe34 100644 --- a/arch/x86/pci/i386.c +++ b/arch/x86/pci/i386.c @@ -282,6 +282,15 @@ int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma, return -EINVAL; prot = pgprot_val(vma->vm_page_prot); + + /* + * Return error if pat is not enabled and write_combine is requested. + * Caller can followup with UC MINUS request and add a WC mtrr if there + * is a free mtrr slot. + */ + if (!pat_enabled && write_combine) + return -EINVAL; + if (pat_enabled && write_combine) prot |= _PAGE_CACHE_WC; else if (pat_enabled || boot_cpu_data.x86 > 3) |