drm/i915: Introduce i915_gem_object_finish_gpu()

... reincarnated from i915_gem_object_flush_gpu(). The semantic
difference is that after calling finish_gpu() the object no longer
resides in any GPU domain, and so will cause the GPU caches to be
invalidated if it is ever used again.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -1190,7 +1190,7 @@ void i915_gem_clflush_object(struct drm_i915_gem_object *obj);
 int __must_check i915_gem_object_set_domain(struct drm_i915_gem_object *obj,
 					    uint32_t read_domains,
 					    uint32_t write_domain);
-int __must_check i915_gem_object_flush_gpu(struct drm_i915_gem_object *obj);
+int __must_check i915_gem_object_finish_gpu(struct drm_i915_gem_object *obj);
 int __must_check i915_gem_init_ringbuffer(struct drm_device *dev);
 void i915_gem_cleanup_ringbuffer(struct drm_device *dev);
 void i915_gem_do_init(struct drm_device *dev,

drivers/gpu/drm/i915/i915_gem.c

@@ -2165,23 +2165,29 @@ i915_gem_object_unbind(struct drm_i915_gem_object *obj)
 		return -EINVAL;
 	}
 
+	ret = i915_gem_object_finish_gpu(obj);
+	if (ret == -ERESTARTSYS)
+		return ret;
+	/* Continue on if we fail due to EIO, the GPU is hung so we
+	 * should be safe and we need to cleanup or else we might
+	 * cause memory corruption through use-after-free.
+	 */
+
 	/* blow away mappings if mapped through GTT */
 	i915_gem_release_mmap(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
-	 * also ensure that all pending GPU writes are finished
-	 * before we unbind.
+	 * are flushed when we go to remap it.
 	 */
+	if (ret == 0)
 		ret = i915_gem_object_set_to_cpu_domain(obj, 1);
 	if (ret == -ERESTARTSYS)
 		return ret;
-	/* Continue on if we fail due to EIO, the GPU is hung so we
-	 * should be safe and we need to cleanup or else we might
-	 * cause memory corruption through use-after-free.
-	 */
 	if (ret) {
+		/* In the event of a disaster, abandon all caches and
+		 * hope for the best.
+		 */
 		i915_gem_clflush_object(obj);
 		obj->base.read_domains = obj->base.write_domain = I915_GEM_DOMAIN_CPU;
 	}
@@ -3045,11 +3051,11 @@ i915_gem_object_set_to_display_plane(struct drm_i915_gem_object *obj,
 }
 
 int
-i915_gem_object_flush_gpu(struct drm_i915_gem_object *obj)
+i915_gem_object_finish_gpu(struct drm_i915_gem_object *obj)
 {
 	int ret;
 
-	if (!obj->active)
+	if ((obj->base.read_domains & I915_GEM_GPU_DOMAINS) == 0)
 		return 0;
 
 	if (obj->base.write_domain & I915_GEM_GPU_DOMAINS) {
@@ -3058,6 +3064,9 @@ i915_gem_object_flush_gpu(struct drm_i915_gem_object *obj)
 			return ret;
 	}
 
+	/* Ensure that we invalidate the GPU's caches and TLBs. */
+	obj->base.read_domains &= ~I915_GEM_GPU_DOMAINS;
+
 	return i915_gem_object_wait_rendering(obj);
 }
 

drivers/gpu/drm/i915/intel_display.c

@@ -1971,7 +1971,7 @@ intel_pipe_set_base(struct drm_crtc *crtc, int x, int y,
 		 * This should only fail upon a hung GPU, in which case we
 		 * can safely continue.
 		 */
-		ret = i915_gem_object_flush_gpu(obj);
+		ret = i915_gem_object_finish_gpu(obj);
 		(void) ret;
 	}