[Bug 103502] GPU HANG: ecode 3:0:0x7c9bf89c, in Xorg [781], reason: Hang on rcs0, action: reset

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=103502

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

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

--- Comment #3 from Chris Wilson <chris at chris-wilson.co.uk> ---
commit 1d033beb20d6d5885587a02a393b6598d766a382
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Tue Oct 31 10:36:07 2017 +0000

    drm/i915: Check incoming alignment for unfenced buffers (on i915gm)

    In case the object has changed tiling between calls to execbuf, we need
    to check if the existing offset inside the GTT matches the new tiling
    constraint. We even need to do this for "unfenced" tiled objects, where
    the 3D commands use an implied fence and so the object still needs to
    match the physical fence restrictions on alignment (only required for
    gen2 and early gen3).

    In commit 2889caa92321 ("drm/i915: Eliminate lots of iterations over
    the execobjects array"), the idea was to remove the second guessing and
    only set the NEEDS_MAP flag when required. However, the entire check
    for an unusable offset for fencing was removed and not just the
    secondary check. I.e.

            /* avoid costly ping-pong once a batch bo ended up non-mappable */
            if (entry->flags & __EXEC_OBJECT_NEEDS_MAP &&
                !i915_vma_is_map_and_fenceable(vma))
                    return !only_mappable_for_reloc(entry->flags);

    was entirely removed as the ping-pong between execbuf passes was fixed,
    but its primary purpose in forcing unaligned unfenced access to be
    rebound was forgotten.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103502
    Fixes: 2889caa92321 ("drm/i915: Eliminate lots of iterations over the
execobjects array")
    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/20171031103607.17836-1-chris@chris-wilson.co.uk
    Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

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