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

Add a more descriptive comment to keep a clear separation
between static property vs runtime changeable.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 include/hw/cpu/a9mpcore.h | 3 ++-
 hw/cpu/a9mpcore.c         | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/hw/cpu/a9mpcore.h b/include/hw/cpu/a9mpcore.h
index 5d67ca22c4..212f5db391 100644
--- a/include/hw/cpu/a9mpcore.h
+++ b/include/hw/cpu/a9mpcore.h
@@ -25,10 +25,11 @@ typedef struct A9MPPrivState {
     SysBusDevice parent_obj;
     /*< public >*/
 
+    /* Properties */
     uint32_t num_cpu;
-    MemoryRegion container;
     uint32_t num_irq;
 
+    MemoryRegion container;
     A9SCUState scu;
     GICState gic;
     A9GTimerState gtimer;
diff --git a/hw/cpu/a9mpcore.c b/hw/cpu/a9mpcore.c
index 642363d2f4..5012c7a81a 100644
--- a/hw/cpu/a9mpcore.c
+++ b/hw/cpu/a9mpcore.c
@@ -176,6 +176,7 @@ static void a9mp_priv_class_init(ObjectClass *klass, void *data)
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->realize = a9mp_priv_realize;
+    dc->vmsd = vmstate_qdev_no_state_to_migrate;
     device_class_set_props(dc, a9mp_priv_properties);
 }
 
-- 
2.21.3