[Bug 101859] [IGT] [BYT] Fail test igt at gem_lut_handle

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101859

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

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

--- Comment #4 from Chris Wilson <chris at chris-wilson.co.uk> ---
commit a575c6761757232ea2c7dc9f370640754b90cc69
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Mon Aug 28 11:46:31 2017 +0100

    drm/i915: Recreate vmapping even when the object is pinned

    Sometimes we know we are the only user of the bo, but since we take a
    protective pin_pages early on, an attempt to change the vmap on the
    object is denied because it is busy. i915_gem_object_pin_map() cannot
    tell from our single pin_count if the operation is safe. Instead we must
    pass that information down from the caller in the manner of
    I915_MAP_OVERRIDE.

    This issue has existed from the introduction of the mapping, but was
    never noticed as the only place where this conflict might happen is for
    cached kernel buffers (such as allocated by i915_gem_batch_pool_get()).
    Until recently there was only a single user (the cmdparser) so no
    conflicts ever occurred. However, we now use it to allocate batches for
    different operations (using MAP_WC on !llc for writes) in addition to the
    existing shadow batch (using MAP_WB for reads).

    We could either keep both mappings cached, or use a different write
    mechanism if we detect a MAP_WB already exists (i.e. clflush
    afterwards), but as we haven't seen this issue in the wild (it requires
    hitting the GPU reloc path in addition to the cmdparser) for simplicity
    just allow the mappings to be recreated.

    v2: Include the i915_MAP_OVERRIDE bit in the enum so the compiler knows
    about all the valid values.

    Fixes: 7dd4f6729f92 ("drm/i915: Async GPU relocation processing")
    Testcase: igt/gem_lut_handle # byt, completely by accident
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
    Link:
https://patchwork.freedesktop.org/patch/msgid/20170828104631.8606-1-chris@chris-wilson.co.uk
    Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

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