drm/virtio: switch virtio_gpu_wait_ioctl() to gem helper.

Use drm_gem_reservation_object_wait() in virtio_gpu_wait_ioctl().
This also makes the ioctl run lockless.

v9: fix return value.
v5: handle lookup failure.
v2: use reservation_object_test_signaled_rcu for VIRTGPU_WAIT_NOWAIT.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20190829103301.3539-3-kraxel@redhat.com

drivers/gpu/drm/virtio/virtgpu_ioctl.c

@@ -466,22 +466,26 @@ static int virtio_gpu_wait_ioctl(struct drm_device *dev, void *data,
 				 struct drm_file *file)
 {
 	struct drm_virtgpu_3d_wait *args = data;
-	struct drm_gem_object *gobj = NULL;
-	struct virtio_gpu_object *qobj = NULL;
+	struct drm_gem_object *obj;
+	long timeout = 15 * HZ;
 	int ret;
-	bool nowait = false;
 
-	gobj = drm_gem_object_lookup(file, args->handle);
-	if (gobj == NULL)
+	obj = drm_gem_object_lookup(file, args->handle);
+	if (obj == NULL)
 		return -ENOENT;
 
-	qobj = gem_to_virtio_gpu_obj(gobj);
-
-	if (args->flags & VIRTGPU_WAIT_NOWAIT)
-		nowait = true;
-	ret = virtio_gpu_object_wait(qobj, nowait);
+	if (args->flags & VIRTGPU_WAIT_NOWAIT) {
+		ret = dma_resv_test_signaled_rcu(obj->resv, true);
+	} else {
+		ret = dma_resv_wait_timeout_rcu(obj->resv, true, true,
+						timeout);
+	}
+	if (ret == 0)
+		ret = -EBUSY;
+	else if (ret > 0)
+		ret = 0;
 
-	drm_gem_object_put_unlocked(gobj);
+	drm_gem_object_put_unlocked(obj);
 	return ret;
 }