drm/i915: Mark untiled BLT commands as fenced on gen2/3

The BLT commands on gen2/3 utilize the fence registers and so we cannot
modify any fences for the object whilst those commands are in flight.
Currently we marked tiled commands as occupying a fence, but forgot to
restrict the untiled commands from preventing a fence being assigned
before they were completed.

One side-effect is that we ten have to double check that a fence was
allocated for a fenced buffer during move-to-active.

Reported-by: Jiri Slaby <jirislaby@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=43427
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=47990
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Testcase: i-g-t/tests/gem_tiled_after_untiled_blt
Tested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 9 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 97e659985223..4c65c639f772 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1472,16 +1472,19 @@ i915_gem_object_move_to_active(struct drm_i915_gem_object *obj,
         list_move_tail(&obj->ring_list, &ring->active_list);
 
         obj->last_rendering_seqno = seqno;
-        if (obj->fenced_gpu_access) {
-                struct drm_i915_fence_reg *reg;
-
-                BUG_ON(obj->fence_reg == I915_FENCE_REG_NONE);
 
+        if (obj->fenced_gpu_access) {
                 obj->last_fenced_seqno = seqno;
                 obj->last_fenced_ring = ring;
 
-                reg = &dev_priv->fence_regs[obj->fence_reg];
-                list_move_tail(&reg->lru_list, &dev_priv->mm.fence_list);
+                /* Bump MRU to take account of the delayed flush */
+                if (obj->fence_reg != I915_FENCE_REG_NONE) {
+                        struct drm_i915_fence_reg *reg;
+
+                        reg = &dev_priv->fence_regs[obj->fence_reg];
+                        list_move_tail(&reg->lru_list,
+                                       &dev_priv->mm.fence_list);
+                }
         }
 }