3 files changed, 50 insertions, 6 deletions

diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 39aec42dae..a076b1e54d 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -150,6 +150,7 @@ static int vhost_user_blk_start(VirtIODevice *vdev)
         error_report("Error starting vhost: %d", -ret);
         goto err_guest_notifiers;
     }
+    s->started_vu = true;
 
     /* guest_notifier_mask/pending not used yet, so just unmask
      * everything here. virtio-pci will do the right thing by
@@ -175,6 +176,11 @@ static void vhost_user_blk_stop(VirtIODevice *vdev)
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     int ret;
 
+    if (!s->started_vu) {
+        return;
+    }
+    s->started_vu = false;
+
     if (!k->set_guest_notifiers) {
         return;
     }
@@ -341,9 +347,7 @@ static void vhost_user_blk_disconnect(DeviceState *dev)
     }
     s->connected = false;
 
-    if (s->dev.started) {
-        vhost_user_blk_stop(vdev);
-    }
+    vhost_user_blk_stop(vdev);
 
     vhost_dev_cleanup(&s->dev);
 }
@@ -399,6 +403,15 @@ static void vhost_user_blk_event(void *opaque, QEMUChrEvent event)
                     NULL, NULL, false);
             aio_bh_schedule_oneshot(ctx, vhost_user_blk_chr_closed_bh, opaque);
         }
+
+        /*
+         * Move vhost device to the stopped state. The vhost-user device
+         * will be clean up and disconnected in BH. This can be useful in
+         * the vhost migration code. If disconnect was caught there is an
+         * option for the general vhost code to get the dev state without
+         * knowing its type (in this case vhost-user).
+         */
+        s->dev.started = false;
         break;
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 8087f200e9..60bc516003 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -871,21 +871,42 @@ 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)
diff --git a/include/hw/virtio/vhost-user-blk.h b/include/hw/virtio/vhost-user-blk.h
index f536576d20..7c91f15040 100644
--- a/include/hw/virtio/vhost-user-blk.h
+++ b/include/hw/virtio/vhost-user-blk.h
@@ -40,7 +40,17 @@ struct VHostUserBlk {
     VhostUserState vhost_user;
     struct vhost_virtqueue *vhost_vqs;
     VirtQueue **virtqs;
+
+    /*
+     * There are at least two steps of initialization of the
+     * vhost-user device. The first is a "connect" step and
+     * second is a "start" step. Make a separation between
+     * those initialization phases by using two fields.
+     */
+    /* vhost_user_blk_connect/vhost_user_blk_disconnect */
     bool connected;
+    /* vhost_user_blk_start/vhost_user_blk_stop */
+    bool started_vu;
 };
 
 #endif