1 files changed, 46 insertions, 3 deletions

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 0119516..68f0a75 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -818,19 +818,41 @@ static int vhost_dev_set_features(struct vhost_dev *dev,
     r = dev->vhost_ops->vhost_set_features(dev, features);
     if (r < 0) {
         VHOST_OPS_DEBUG("vhost_set_features failed");
+        goto out;
+    }
+    if (dev->vhost_ops->vhost_set_backend_cap) {
+        r = dev->vhost_ops->vhost_set_backend_cap(dev);
+        if (r < 0) {
+            VHOST_OPS_DEBUG("vhost_set_backend_cap failed");
+            goto out;
+        }
     }
+
+out:
     return r < 0 ? -errno : 0;
 }
 
 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) {
@@ -861,21 +883,42 @@ static int vhost_migration_log(MemoryListener *listener, bool enable)
         dev->log_enabled = enable;
         return 0;
     }
+
+    r = 0;
     if (!enable) {
         r = vhost_dev_set_log(dev, false);
         if (r < 0) {
-            return r;
+            goto check_dev_state;
         }
         vhost_log_put(dev, false);
     } else {
         vhost_dev_log_resize(dev, vhost_get_log_size(dev));
         r = vhost_dev_set_log(dev, true);
         if (r < 0) {
-            return r;
+            goto check_dev_state;
         }
     }
+
+check_dev_state:
     dev->log_enabled = enable;
-    return 0;
+    /*
+     * vhost-user-* devices could change their state during log
+     * initialization due to disconnect. So check dev state after
+     * vhost communication.
+     */
+    if (!dev->started) {
+        /*
+         * Since device is in the stopped state, it is okay for
+         * migration. Return success.
+         */
+        r = 0;
+    }
+    if (r) {
+        /* An error is occured. */
+        dev->log_enabled = false;
+    }
+
+    return r;
 }
 
 static void vhost_log_global_start(MemoryListener *listener)