From: Amit Shah <amit.shah@redhat.com>
Date: Thu, 1 Jul 2010 09:28:16 +0000 (+0530)
Subject: virtio-serial: Check if virtio queue is ready before consuming data
X-Git-Tag: xen-15-06-02~7260
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=6b611d3ab820d6e3b30a23ebac69df04ab0105a0;p=people%2Fsstabellini%2Fqemu-dm.git%2F.git

virtio-serial: Check if virtio queue is ready before consuming data

If a virtio-serial port is removed before the guest comes up and
initialises the virtqueues, qemu exits with the message

Guest moved used index from 0 to 61440

This happens because we try to clear any pending buffers from the
virtqueue.

Ensure the virtqueue is initialised before calling any virtqueue
operations.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---

diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
index 26d5841154..077c3183bc 100644
--- a/hw/virtio-serial-bus.c
+++ b/hw/virtio-serial-bus.c
@@ -139,6 +139,9 @@ static void flush_queued_data(VirtIOSerialPort *port, bool discard)
 {
     assert(port);
 
+    if (!virtio_queue_ready(port->ovq)) {
+        return;
+    }
     do_flush_queued_data(port, port->ovq, &port->vser->vdev, discard);
 }