[PATCH 11/11] drm/virtio: rework virtio_gpu_enable_notify

[Chia-I Wu]

Call virtqueue_kick_prepare once in virtio_gpu_enable_notify, not
whenever a command is added.  This should be more efficient since
the intention is to batch commands.

Signed-off-by: Chia-I Wu <olvaffe at gmail.com>
---
 drivers/gpu/drm/virtio/virtgpu_drv.h |  1 -
 drivers/gpu/drm/virtio/virtgpu_vq.c  | 28 +++++++++++++++++-----------
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h
index f7520feb39d4b..f0e7130ac9e27 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -179,7 +179,6 @@ struct virtio_gpu_device {
 	bool vqs_ready;
 
 	bool disable_notify;
-	bool pending_notify;
 
 	struct ida	resource_ida;
 
diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
index 0961475e68105..aea1be68e99c4 100644
--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -364,16 +364,13 @@ static void virtio_gpu_queue_ctrl_sgs(struct virtio_gpu_device *vgdev,
 
 	trace_virtio_gpu_cmd_queue(vq, virtio_gpu_vbuf_ctrl_hdr(vbuf));
 
-	notify = virtqueue_kick_prepare(vq);
+	if (!vgdev->disable_notify)
+		notify = virtqueue_kick_prepare(vq);
 
 	spin_unlock(&vgdev->ctrlq.qlock);
 
-	if (notify) {
-		if (vgdev->disable_notify)
-			vgdev->pending_notify = true;
-		else
-			virtqueue_notify(vq);
-	}
+	if (notify)
+		virtqueue_notify(vq);
 }
 
 static void virtio_gpu_queue_fenced_ctrl_buffer(struct virtio_gpu_device *vgdev,
@@ -436,12 +433,21 @@ void virtio_gpu_disable_notify(struct virtio_gpu_device *vgdev)
 
 void virtio_gpu_enable_notify(struct virtio_gpu_device *vgdev)
 {
+	struct virtqueue *vq = vgdev->ctrlq.vq;
+	bool notify;
+
 	vgdev->disable_notify = false;
 
-	if (!vgdev->pending_notify)
-		return;
-	vgdev->pending_notify = false;
-	virtqueue_notify(vgdev->ctrlq.vq);
+	spin_lock(&vgdev->ctrlq.qlock);
+	notify = virtqueue_kick_prepare(vq);
+	spin_unlock(&vgdev->ctrlq.qlock);
+
+	/* Do not call virtqueue_notify with the lock held because
+	 * virtio_gpu_dequeue_ctrl_func may contend for the lock if an irq is
+	 * generated while we are in virtqueue_notify.
+	 */
+	if (notify)
+		virtqueue_notify(vq);
 }
 
 static void virtio_gpu_queue_ctrl_buffer(struct virtio_gpu_device *vgdev,
-- 
2.25.0.341.g760bfbb309-goog