it's one of these commits (from the quantal kernel), likely the top one since it's happening on sandybridge:
817e8fdee14b05d drm/i915: Implement WaDisableHiZPlanesWhenMSAAEnabled 4c443ec9afe7f6f drm/i915: GFX_MODE Flush TLB Invalidate Mode must be '1' for scanline waits f534135423c7028 drm/i915: Disable AsyncFlip performance optimisations c0c1fd8a18479f0 drm/i915: Invalidate the relocation presumed_offsets along the slow path
it's one of these commits (from the quantal kernel), likely the top one since it's happening on sandybridge:
817e8fdee14b05d drm/i915: Implement WaDisableHiZPla nesWhenMSAAEnab led
4c443ec9afe7f6f drm/i915: GFX_MODE Flush TLB Invalidate Mode must be '1' for scanline waits
f534135423c7028 drm/i915: Disable AsyncFlip performance optimisations
c0c1fd8a18479f0 drm/i915: Invalidate the relocation presumed_offsets along the slow path