From: Dima Stepanov <dimastep@yandex-team.ru>

If the vhost-user-blk daemon provides only one virtqueue, but device was
added with several queues, then QEMU will send more VHOST-USER command
than expected by daemon side. The vhost_virtqueue_start() routine
handles such case by checking the return value from the
virtio_queue_get_desc_addr() function call. Add the same check to the
vhost_dev_set_log() routine.

Signed-off-by: Dima Stepanov <dimastep@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <6232946d5af09e9775076645909964a6539b8ab5.1599813294.git.dimastep@yandex-team.ru>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio/vhost.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 1b2d735b54..7c9542b1f6 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -835,12 +835,24 @@ out:
 static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log)
 {
     int r, i, idx;
+    hwaddr addr;
+
     r = vhost_dev_set_features(dev, enable_log);
     if (r < 0) {
         goto err_features;
     }
     for (i = 0; i < dev->nvqs; ++i) {
         idx = dev->vhost_ops->vhost_get_vq_index(dev, dev->vq_index + i);
+        addr = virtio_queue_get_desc_addr(dev->vdev, idx);
+        if (!addr) {
+            /*
+             * The queue might not be ready for start. If this
+             * is the case there is no reason to continue the process.
+             * The similar logic is used by the vhost_virtqueue_start()
+             * routine.
+             */
+            continue;
+        }
         r = vhost_virtqueue_set_addr(dev, dev->vqs + i, idx,
                                      enable_log);
         if (r < 0) {
-- 
MST