[Bug 108315] [CI][BAT] icl incomplete - GEM_BUG_ON(!i915_request_completed(rq)) / GEM_BUG_ON(buf[2 * head + 1] != port->context_id) HSDES#:1806554093

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108315

Mika Kuoppala <mika.kuoppala at intel.com> changed:

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

--- Comment #30 from Mika Kuoppala <mika.kuoppala at intel.com> ---
Optimistically but with a grain of confidence: 
commit d8f505311717cfc2033c44a8b26ba96c66187303
Author: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Date:   Wed Dec 5 15:46:12 2018 +0200

    drm/i915/icl: Forcibly evict stale csb entries

    Gen11 fails to deliver wrt global observation point on
    tail/entry updates and we sometimes see old entry.

    Use clflush to forcibly evict our possibly stale copy
    of the cacheline in hopes that we get fresh one from gpu.
    Obviously there is something amiss in the coherency protocol so
    this can be consired as a workaround until real cause
    is found.

    The working hardware will do the evict without our cue anyways,
    so the cost in there should be ameliorated by that fact.

    v2: for next pass, s/flush/evict, add reset (Chris)

    References: https://bugzilla.freedesktop.org/show_bug.cgi?id=108315
    Cc: Chris Wilson <chris at chris-wilson.co.uk>
    Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
    Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
    Link:
https://patchwork.freedesktop.org/patch/msgid/20181205134612.24822-1-mika.kuoppala@linux.intel.com

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