Comment 63 for bug 1339939

I haven't had any other inspiration. Maybe,

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 401f3e7..ccb0e5c 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -513,6 +513,7 @@ reset:
         * registers with the above sequence (the readback of the HEAD registers
         * also enforces ordering), otherwise the hw might lose the new ring
         * register values. */
+ memset(ring->virtual_start, 0, ring->size);
        I915_WRITE_START(ring, i915_gem_obj_ggtt_offset(obj));
        I915_WRITE_CTL(ring,
                        ((ring->size - PAGE_SIZE) & RING_NR_PAGES)