virtio-serial: Make sure virtqueue is ready before discarding data

This can happen if a port gets unplugged before guest has chance to
initialise vqs.

Reported-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit 7185f9315bcf90e99b123370cf4d19b8c20afbd5)

diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
index 09e22aa44a2cdd031ce3e4b657453751cdc55fad..e05ab5e609691f0b04b55f061d16a5302455dfe3 100644 (file)
--- a/hw/virtio-serial-bus.c
+++ b/hw/virtio-serial-bus.c
@@ -117,6 +117,9 @@ static void discard_vq_data(VirtQueue *vq, VirtIODevice *vdev)
 {
     VirtQueueElement elem;
 
+    if (!virtio_queue_ready(vq)) {
+        return;
+    }
     while (virtqueue_pop(vq, &elem)) {
         virtqueue_push(vq, &elem, 0);
     }