lkml.org 
[lkml]   [2010]   [Jan]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[24/29] x86/PCI/PAT: return EINVAL for pci mmap WC request for !pat_enabled
    From: Suresh Siddha <suresh.b.siddha@intel.com>

    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>

    ---
    arch/x86/pci/i386.c | 9 +++++++++
    1 file changed, 9 insertions(+)

    --- a/arch/x86/pci/i386.c
    +++ b/arch/x86/pci/i386.c
    @@ -282,6 +282,15 @@ int pci_mmap_page_range(struct pci_dev *
    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)



    \
     
     \ /
      Last update: 2010-01-23 01:21    [W:4.122 / U:1.688 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site