drm/i915: Always reset vma->ggtt_view.pages cache on unbinding
commit 016a65a3 upstream. With the introduction of multiple views of an obj in the same vm, each vma was taught to cache its copy of the pages (so that different views could have different page arrangements). However, this missed decoupling those vma->ggtt_view.pages when the vma released its reference on the obj->pages. As we don't always free the vma, this leads to a possible scenario (e.g. execbuffer interrupted by the shrinker) where the vma points to a stale obj->pages, and explodes. Fixes regression from commit fe14d5f4 Author: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Date: Wed Dec 10 17:27:58 2014 +0000 drm/i915: Infrastructure for supporting different GGTT views per object Tvrtko says, if someone else will be confused how this can happen, key is the reservation execbuffer path. That puts the VMA on the exec_list which prevents i915_vma_unbind and i915_gem_vma_destroy from fully destroying the VMA. So the VMA is left existing as an empty object in the list - unbound and disassociated with the backing store. Kind of a cached memory object. And then re-using it needs to clear the cached pages pointer which is fixed above. Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1227892Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Michel Thierry <michel.thierry@intel.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> [Jani: Added Tvrtko's explanation to commit message.] Signed-off-by: Jani Nikula <jani.nikula@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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