vhost: flush dev once during vhost_dev_stop

When vhost_work_dev_flush returns all work queued at that time will have
completed. There is then no need to flush after every vhost_poll_stop
call, and we can move the flush call to after the loop that stops the
pollers.
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20220517180850.198915-3-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vhost.c

@@ -653,11 +653,11 @@ void vhost_dev_stop(struct vhost_dev *dev)
 	int i;
 
 	for (i = 0; i < dev->nvqs; ++i) {
-		if (dev->vqs[i]->kick && dev->vqs[i]->handle_kick) {
+		if (dev->vqs[i]->kick && dev->vqs[i]->handle_kick)
 			vhost_poll_stop(&dev->vqs[i]->poll);
-			vhost_work_dev_flush(dev->vqs[i]->poll.dev);
-		}
 	}
+
+	vhost_work_dev_flush(dev);
 }
 EXPORT_SYMBOL_GPL(vhost_dev_stop);