hw/core/machine: Use qemu_register_resettable for sysbus reset

Move the reset of the sysbus (and thus all devices and buses anywhere
on the qbus tree) from qemu_register_reset() to qemu_register_resettable().

This is a behaviour change: because qemu_register_resettable() is
aware of three-phase reset, this now means that:
 * 'enter' phase reset methods of devices and buses are called
   before any legacy reset callbacks registered with qemu_register_reset()
 * 'exit' phase reset methods of devices and buses are called
   after any legacy qemu_register_reset() callbacks

Put another way, a qemu_register_reset() callback is now correctly
ordered in the 'hold' phase along with any other 'hold' phase methods.

The motivation for doing this is that we will now be able to resolve
some reset-ordering issues using the three-phase mechanism, because
the 'exit' phase is always after the 'hold' phase, even when the
'hold' phase function was registered with qemu_register_reset().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20240220160622.114437-10-peter.maydell@linaro.org
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>

hw/core/machine.c

@@ -1577,14 +1577,13 @@ void qdev_machine_creation_done(void)
     /* TODO: once all bus devices are qdevified, this should be done
      * when bus is created by qdev.c */
     /*
-     * TODO: If we had a main 'reset container' that the whole system
-     * lived in, we could reset that using the multi-phase reset
-     * APIs. For the moment, we just reset the sysbus, which will cause
+     * This is where we arrange for the sysbus to be reset when the
+     * whole simulation is reset. In turn, resetting the sysbus will cause
      * all devices hanging off it (and all their child buses, recursively)
      * to be reset. Note that this will *not* reset any Device objects
      * which are not attached to some part of the qbus tree!
      */
-    qemu_register_reset(resettable_cold_reset_fn, sysbus_get_default());
+    qemu_register_resettable(OBJECT(sysbus_get_default()));
 
     notifier_list_notify(&machine_init_done_notifiers, NULL);