qdev: add qdev_add_vm_change_state_handler()

Children sometimes depend on their parent's vm change state handler
having completed.  Add a vm change state handler API for devices that
guarantees tree depth ordering.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

hw/core/Makefile.objs

@@ -7,6 +7,7 @@ common-obj-$(CONFIG_SOFTMMU) += fw-path-provider.o
 common-obj-y += irq.o
 common-obj-y += hotplug.o
 common-obj-$(CONFIG_SOFTMMU) += nmi.o
+common-obj-$(CONFIG_SOFTMMU) += vm-change-state-handler.o
 
 common-obj-$(CONFIG_EMPTY_SLOT) += empty_slot.o
 common-obj-$(CONFIG_XILINX_AXI) += stream.o

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

@@ -0,0 +1,61 @@
+/*
+ *  qdev vm change state handlers
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License,
+ *  or (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "hw/qdev.h"
+
+static int qdev_get_dev_tree_depth(DeviceState *dev)
+{
+    int depth;
+
+    for (depth = 0; dev; depth++) {
+        BusState *bus = dev->parent_bus;
+
+        if (!bus) {
+            break;
+        }
+
+        dev = bus->parent;
+    }
+
+    return depth;
+}
+
+/**
+ * qdev_add_vm_change_state_handler:
+ * @dev: the device that owns this handler
+ * @cb: the callback function to be invoked
+ * @opaque: user data passed to the callback function
+ *
+ * This function works like qemu_add_vm_change_state_handler() except callbacks
+ * are invoked in qdev tree depth order.  Ordering is desirable when callbacks
+ * of children depend on their parent's callback having completed first.
+ *
+ * For example, when qdev_add_vm_change_state_handler() is used, a host
+ * controller's callback is invoked before the children on its bus when the VM
+ * starts running.  The order is reversed when the VM stops running.
+ *
+ * Returns: an entry to be freed with qemu_del_vm_change_state_handler()
+ */
+VMChangeStateEntry *qdev_add_vm_change_state_handler(DeviceState *dev,
+                                                     VMChangeStateHandler *cb,
+                                                     void *opaque)
+{
+    int depth = qdev_get_dev_tree_depth(dev);
+
+    return qemu_add_vm_change_state_handler_prio(cb, opaque, depth);
+}

include/hw/qdev-core.h

@@ -6,6 +6,7 @@
 #include "qom/object.h"
 #include "hw/irq.h"
 #include "hw/hotplug.h"
+#include "sysemu/sysemu.h"
 
 enum {
     DEV_NVECTORS_UNSPECIFIED = -1,
@@ -450,4 +451,8 @@ static inline bool qbus_is_hotpluggable(BusState *bus)
 void device_listener_register(DeviceListener *listener);
 void device_listener_unregister(DeviceListener *listener);
 
+VMChangeStateEntry *qdev_add_vm_change_state_handler(DeviceState *dev,
+                                                     VMChangeStateHandler *cb,
+                                                     void *opaque);
+
 #endif