qbus: register reset handler for qbus whose parent is NULL

Stefan Weil reported the regression caused by
ec990eb622 as follows

> The second regression also occurs with MIPS malta.
> Networking no longer works with the default pcnet nic.
>
> This is caused because the reset function for pcnet is no
> longer called during system boot. The result in an invalid
> mac address (all zero) and a non-working nic.
>
> For this second regression I still have no simple solution.
> Of course mips_malta.c should be converted to qdev which
> would fix both problems (but only for malta system emulation).

The issue is, it is assumed that all qbuses, qdeves are under
main_system_bus. But there are qbuses whose parent is NULL. So it
is necessary to trigger reset for those qbuses.
(On the other hand, if NULL is passed to qdev_create(), its parent bus
is main_system_bus.)
Ideally those buses should be moved under bus controller
device which is qdev. But it's not done yet.
So register qbus reset handler for qbus whose parent is NULL.

Reported-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/qdev.c

@@ -333,6 +333,12 @@ void qbus_reset_all(BusState *bus)
     qbus_walk_children(bus, qdev_reset_one, qbus_reset_one, NULL);
 }
 
+void qbus_reset_all_fn(void *opaque)
+{
+    BusState *bus = opaque;
+    qbus_reset_all(bus);
+}
+
 /* can be used as ->unplug() callback for the simple cases */
 int qdev_simple_unplug_cb(DeviceState *dev)
 {
@@ -754,8 +760,11 @@ void qbus_create_inplace(BusState *bus, BusInfo *info,
     if (parent) {
         QLIST_INSERT_HEAD(&parent->child_bus, bus, sibling);
         parent->num_child_bus++;
+    } else if (bus != main_system_bus) {
+        /* TODO: once all bus devices are qdevified,
+           only reset handler for main_system_bus should be registered here. */
+        qemu_register_reset(qbus_reset_all_fn, bus);
     }
-
 }
 
 BusState *qbus_create(BusInfo *info, DeviceState *parent, const char *name)
@@ -778,6 +787,9 @@ void qbus_free(BusState *bus)
     if (bus->parent) {
         QLIST_REMOVE(bus, sibling);
         bus->parent->num_child_bus--;
+    } else {
+        assert(bus != main_system_bus); /* main_system_bus is never freed */
+        qemu_unregister_reset(qbus_reset_all_fn, bus);
     }
     qemu_free((void*)bus->name);
     if (bus->qdev_allocated) {

hw/qdev.h

@@ -199,6 +199,8 @@ int qdev_walk_children(DeviceState *dev, qdev_walkerfn *devfn,
                        qbus_walkerfn *busfn, void *opaque);
 void qdev_reset_all(DeviceState *dev);
 void qbus_reset_all(BusState *bus);
+void qbus_reset_all_fn(void *opaque);
+
 void qbus_free(BusState *bus);
 
 #define FROM_QBUS(type, dev) DO_UPCAST(type, qbus, dev)

vl.c

@@ -3088,7 +3088,9 @@ int main(int argc, char **argv, char **envp)
         exit(1);
     }
 
-    qemu_register_reset((void *)qbus_reset_all, sysbus_get_default());
+    /* TODO: once all bus devices are qdevified, this should be done
+     * when bus is created by qdev.c */
+    qemu_register_reset(qbus_reset_all_fn, sysbus_get_default());
     qemu_run_machine_init_done_notifiers();
 
     qemu_system_reset();