[Intel-gfx] [PATCH 3/4] drm/i915: Only skip updating execobject.offset after error

[Joonas Lahtinen]

On pe, 2017-07-21 at 15:50 +0100, Chris Wilson wrote:
> I was being overly paranoid in not updating the execobject.offset after
> performing the fallback copy where we set reloc.presumed_offset to -1.
> The thinking was to ensure that a subsequent NORELOC execbuf would be
> forced to process the invalid relocations. However this is overkill so
> long as we *only* update the execobject.offset following a successful
> update of the relocation value witin the batch. If we have to repeat the
> execbuf due to a later interruption, then we may skip the relocations on
> the second pass (honouring NORELOC) since the execobject.offset match
> the actual offsets (even though reloc.presumed_offset is garbage).
> 
> Subsequent calls to execbuf with NORELOC should themselves ensure that
> the reloc.presumed_offset have been corrected in case of future
> migration.
> 
> Reporting back the actual execobject.offset, even when
> reloc.presumed_offset is garbage, ensures that reuse of those objects
> use the latest information to avoid relocations.
> 
> Fixes: 2889caa92321 ("drm/i915: Eliminate lots of iterations over the execobjects array")
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101635
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation