diff --git a/hw/virtio.c b/hw/virtio.c
index bb994c9b51..5615b59a6c 100644
--- a/hw/virtio.c
+++ b/hw/virtio.c
@@ -209,6 +209,10 @@ void virtio_queue_set_notification(VirtQueue *vq, int enable)
     } else {
         vring_used_flags_set_bit(vq, VRING_USED_F_NO_NOTIFY);
     }
+    if (enable) {
+        /* Expose avail event/used flags before caller checks the avail idx. */
+        smp_mb();
+    }
 }
 
 int virtio_queue_ready(VirtQueue *vq)