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drm/i915/gem: Flush coherency domains on first set-domain-ioctl
Avoid skipping what appears to be a no-op set-domain-ioctl if the cache coherency state is inconsistent with our target domain. This also has the utility of using the population of the pages to validate the backing store. The danger in skipping the first set-domain is leaving the cache inconsistent and submitting stale data, or worse leaving the clean data in the cache and not flushing it to the GPU. The impact should be small as it requires a no-op set-domain as the very first ioctl in a particular sequence not found in typical userspace. Reported-by: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com> Fixes: 754a254 ("drm/i915: Skip object locking around a no-op set-domain ioctl") Testcase: igt/gem_mmap_offset/blt-coherency Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Matthew Auld <matthew.william.auld@gmail.com> Cc: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com> Cc: <stable@vger.kernel.org> # v5.2+ Reviewed-by: Matthew Auld <matthew.auld@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20201019203825.10966-1-chris@chris-wilson.co.uk (cherry picked from commit 44c2200) Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
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