vhost: fix memslot limit check

Since used_memslots will be updated to the actual value after
registering memory listener for the first time, move the
memslots limit checking to the right place.
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>
Signed-off-by: NJay Zhou <jianjay.zhou@huawei.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/virtio/vhost.c

@@ -1106,13 +1106,6 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
         goto fail;
     }
 
-    if (used_memslots > hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) {
-        error_report("vhost backend memory slots limit is less"
-                " than current number of present memory slots");
-        r = -1;
-        goto fail;
-    }
-
     r = hdev->vhost_ops->vhost_set_owner(hdev);
     if (r < 0) {
         VHOST_OPS_DEBUG("vhost_set_owner failed");
@@ -1192,6 +1185,18 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
     hdev->started = false;
     memory_listener_register(&hdev->memory_listener, &address_space_memory);
     QLIST_INSERT_HEAD(&vhost_devices, hdev, entry);
+
+    if (used_memslots > hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) {
+        error_report("vhost backend memory slots limit is less"
+                " than current number of present memory slots");
+        r = -1;
+        if (busyloop_timeout) {
+            goto fail_busyloop;
+        } else {
+            goto fail;
+        }
+    }
+
     return 0;
 
 fail_busyloop: