qdev: Add qdev_add_vm_change_state_handler_full()

Add qdev_add_vm_change_state_handler_full() variant that allows setting
a prepare callback in addition to the main callback.

This will facilitate adding P2P support for VFIO migration in the
following patches.

Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Tested-by: YangHang Liu <yanghliu@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/core/vm-change-state-handler.c

diff --git a/hw/core/vm-change-state-handler.c b/hw/core/vm-change-state-handler.c
index 1f36309..8e26392 100644
--- a/hw/core/vm-change-state-handler.c
+++ b/hw/core/vm-change-state-handler.c
@@ -56,7 +56,19 @@
                                                      VMChangeStateHandler *cb,
                                                      void *opaque)
 {
+    return qdev_add_vm_change_state_handler_full(dev, cb, NULL, opaque);
+}
+
+/*
+ * Exactly like qdev_add_vm_change_state_handler() but passes a prepare_cb
+ * argument too.
+ */
+VMChangeStateEntry *qdev_add_vm_change_state_handler_full(
+    DeviceState *dev, VMChangeStateHandler *cb,
+    VMChangeStateHandler *prepare_cb, void *opaque)
+{
     int depth = qdev_get_dev_tree_depth(dev);
 
-    return qemu_add_vm_change_state_handler_prio(cb, opaque, depth);
+    return qemu_add_vm_change_state_handler_prio_full(cb, prepare_cb, opaque,
+                                                      depth);
 }

include/sysemu/runstate.h

diff --git a/include/sysemu/runstate.h b/include/sysemu/runstate.h
index 764a0fc..08afb97 100644
--- a/include/sysemu/runstate.h
+++ b/include/sysemu/runstate.h
@@ -23,6 +23,9 @@
 VMChangeStateEntry *qdev_add_vm_change_state_handler(DeviceState *dev,
                                                      VMChangeStateHandler *cb,
                                                      void *opaque);
+VMChangeStateEntry *qdev_add_vm_change_state_handler_full(
+    DeviceState *dev, VMChangeStateHandler *cb,
+    VMChangeStateHandler *prepare_cb, void *opaque);
 void qemu_del_vm_change_state_handler(VMChangeStateEntry *e);
 /**
  * vm_state_notify: Notify the state of the VM