vhost: send SET_VRING_ENABLE at start/stop

Send SET_VRING_ENABLE at start/stop, to give the backend
an explicit sign of our state.

Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index de29968a7945b6f1c9f4cf4c27d86ef9a0bea81f..1794f0d211f912077f670be07e050a5a7b071be6 100644 (file)
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1226,6 +1226,11 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
         }
     }
 
+    if (hdev->vhost_ops->vhost_set_vring_enable) {
+        /* only enable first vq pair by default */
+        hdev->vhost_ops->vhost_set_vring_enable(hdev, hdev->vq_index == 0);
+    }
+
     return 0;
 fail_log:
     vhost_log_put(hdev, false);
@@ -1256,6 +1261,10 @@ void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev)
                              hdev->vq_index + i);
     }
 
+    if (hdev->vhost_ops->vhost_set_vring_enable) {
+        hdev->vhost_ops->vhost_set_vring_enable(hdev, 0);
+    }
+
     vhost_log_put(hdev, true);
     hdev->started = false;
     hdev->log = NULL;