[Bug 99274] map_gtt reading/writing data mismatch during the GPU reset

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99274

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEEDINFO                    |RESOLVED

--- Comment #4 from Chris Wilson <chris at chris-wilson.co.uk> ---
commit b1ed35d9179bc42c5ac7b86548cfae589be17b3e
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Wed Jan 4 14:51:10 2017 +0000

    drm/i915: Revoke fenced GTT mmapings across GPU reset

    The fence registers are clobbered by a GPU reset. If there is concurrent
    user access to a fenced region via a GTT mmaping, the access will not be
    fenced during the reset (until we restore the fences afterwards). In order
    to prevent invalid access during the reset, before we clobber the fences
    first we must invalidate the GTT mmapings. Access to the mmap will then
    be forced to fault in the page, and in handling the fault, i915_gem_fault()
    will take the struct_mutex and wait upon the reset to complete.

    v2: Fix up commentary.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99274
    Testcase: igt/gem_mmap_gtt/hang
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Link:
http://patchwork.freedesktop.org/patch/msgid/20170104145110.1486-1-chris@chris-wilson.co.uk
    Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

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