This device doesn't have fields to migrate. Be explicit
by using vmstate_qdev_no_state_to_migrate.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 hw/cpu/cluster.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/cpu/cluster.c b/hw/cpu/cluster.c
index e444b7c29d..95653a643a 100644
--- a/hw/cpu/cluster.c
+++ b/hw/cpu/cluster.c
@@ -80,6 +80,7 @@ static void cpu_cluster_class_init(ObjectClass *klass, void *data)
 
     device_class_set_props(dc, cpu_cluster_properties);
     dc->realize = cpu_cluster_realize;
+    dc->vmsd = vmstate_qdev_no_state_to_migrate;
 
     /* This is not directly for users, CPU children must be attached by code */
     dc->user_creatable = false;
-- 
2.21.3