[Bug 111753] [CI][BAT] igt at i915_selftest@live_gtt - dmesg-fail - igt_cs_tlb failed with error -22

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111753

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

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

--- Comment #2 from Chris Wilson <chris at chris-wilson.co.uk> ---
commit c45e788d95b470e9f68fabe1f3cb44beb5dd7840 (HEAD -> drm-intel-next-queued,
drm-intel/drm-intel-next-queued)
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Thu Sep 19 16:18:11 2019 +0100

    drm/i915/tgl: Suspend pre-parser across GTT invalidations

    Before we execute a batch, we must first issue any and all TLB
    invalidations so that batch picks up the new page table entries.
    Tigerlake's preparser is weakening our post-sync CS_STALL inside the
    invalidate pipe-control and allowing the loading of the batch buffer
    before we have setup its page table (and so it loads the wrong page and
    executes indefinitely).

    The igt_cs_tlb indicates that this issue can only be observed on rcs,
    even though the preparser is common to all engines. Alternatively, we
    could do TLB shootdown via mmio on updating the GTT.

    By inserting the pre-parser disable inside EMIT_INVALIDATE, we will also
    accidentally fixup execution that writes into subsequent batches, such
    as gem_exec_whisper and even relocations performed on the GPU. We should
    be careful not to allow this disable to become baked into the uABI! The
    issue is that if userspace relies on our disabling of the HW
    optimisation, when we are ready to enable that optimisation, userspace
    will then be broken...

    Testcase: igt/i915_selftests/live_gtt/igt_cs_tlb
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111753
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
    Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
    Acked-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
    Link:
https://patchwork.freedesktop.org/patch/msgid/20190919151811.9526-1-chris@chris-wilson.co.uk

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