vhost: fix miration during device start

We need to know ring layout to allocate log buffer.
So init rings first.

Also fixes a theoretical memory-leak-on-error.

https://bugzilla.redhat.com/show_bug.cgi?id=615228Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Tested-by: NGerd Hoffmann <kraxel@redhat.com>

hw/vhost.c

@@ -659,6 +659,16 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
         r = -errno;
         goto fail;
     }
+    for (i = 0; i < hdev->nvqs; ++i) {
+        r = vhost_virtqueue_init(hdev,
+                                 vdev,
+                                 hdev->vqs + i,
+                                 i);
+        if (r < 0) {
+            goto fail_vq;
+        }
+    }
+
     if (hdev->log_enabled) {
         hdev->log_size = vhost_get_log_size(hdev);
         hdev->log = hdev->log_size ?
@@ -667,19 +677,10 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
                   (uint64_t)(unsigned long)hdev->log);
         if (r < 0) {
             r = -errno;
-            goto fail;
-        }
-    }
-
-    for (i = 0; i < hdev->nvqs; ++i) {
-        r = vhost_virtqueue_init(hdev,
-                                 vdev,
-                                 hdev->vqs + i,
-                                 i);
-        if (r < 0) {
             goto fail_vq;
         }
     }
+
     hdev->started = true;
 
     return 0;