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Chris Wilson authored
This effectively reverts commit afcd950c Author: Chris Wilson <chris@chris-wilson.co.uk> Date: Wed Jun 10 15:58:01 2015 +0100 drm: Avoid the double clflush on the last cache line in drm_clflush_virt_range() as we have observed issues with serialisation of the clflush operations on Baytrail+ Atoms with partial updates. Applying the double flush on the last cacheline forces that clflush to be ordered with respect to the previous clflush, and the mfence then protects against prefetches crossing the clflush boundary. The same issue can be demonstrated in userspace with igt/gem_exec_flush. Fixes: afcd950c (drm: Avoid the double clflush on the last cache...) Testcase: igt/gem_concurrent_blit Testcase: igt/gem_partial_pread_pwrite Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92845Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: dri-devel@lists.freedesktop.org Cc: Akash Goel <akash.goel@intel.com> Cc: Imre Deak <imre.deak@intel.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Jason Ekstrand <jason.ekstrand@intel.com> Cc: stable@vger.kernel.org Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1467880930-23082-6-git-send-email-chris@chris-wilson.co.uk
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