drm/i915: Zap mmaps of objects before unbinding them from the GTT.

Otherwise, some other userland writing into its buffer may race to land
writes either after the CPU thinks it's got a coherent view, or after its
GTT entries have been redirected to point at the scratch page.  Either
result is unpleasant.

Signed-off-by: Eric Anholt <eric@anholt.net>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 954fb69..f3758f9 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1915,6 +1915,12 @@ i915_gem_object_unbind(struct drm_gem_object *obj)
                return -EINVAL;
        }
 
+       /* blow away mappings if mapped through GTT */
+       i915_gem_release_mmap(obj);
+
+       if (obj_priv->fence_reg != I915_FENCE_REG_NONE)
+               i915_gem_clear_fence_reg(obj);
+
        /* Move the object to the CPU domain to ensure that
         * any possible CPU writes while it's not in the GTT
         * are flushed when we go to remap it. This will
@@ -1928,20 +1934,14 @@ i915_gem_object_unbind(struct drm_gem_object *obj)
                return ret;
        }
 
+       BUG_ON(obj_priv->active);
+
        if (obj_priv->agp_mem != NULL) {
                drm_unbind_agp(obj_priv->agp_mem);
                drm_free_agp(obj_priv->agp_mem, obj->size / PAGE_SIZE);
                obj_priv->agp_mem = NULL;
        }
 
-       BUG_ON(obj_priv->active);
-
-       /* blow away mappings if mapped through GTT */
-       i915_gem_release_mmap(obj);
-
-       if (obj_priv->fence_reg != I915_FENCE_REG_NONE)
-               i915_gem_clear_fence_reg(obj);
-
        i915_gem_object_put_pages(obj);
 
        if (obj_priv->gtt_space) {