hw/xen: Have legacy Xen backend inherit from DYNAMIC_SYS_BUS_DEVICE

Because the legacy Xen backend devices can optionally be plugged on the
TYPE_PLATFORM_BUS_DEVICE, have it inherit TYPE_DYNAMIC_SYS_BUS_DEVICE.
Remove the implicit TYPE_XENSYSDEV instance_size.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alexander Graf <graf@amazon.com>
Tested-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Bernhard Beschow <shentey@gmail.com>
Message-Id: <20250125181343.59151-10-philmd@linaro.org>

hw/xen/xen-legacy-backend.c

@@ -640,16 +640,14 @@ static void xendev_class_init(ObjectClass *klass, void *data)
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     set_bit(DEVICE_CATEGORY_MISC, dc->categories);
-    /* xen-backend devices can be plugged/unplugged dynamically */
-    dc->user_creatable = true;
     dc->bus_type = TYPE_XENSYSBUS;
 }
 
 static const TypeInfo xendev_type_info = {
     .name          = TYPE_XENBACKEND,
-    .parent        = TYPE_DEVICE,
+    .parent        = TYPE_DYNAMIC_SYS_BUS_DEVICE,
     .class_init    = xendev_class_init,
-    .instance_size = sizeof(struct XenLegacyDevice),
+    .instance_size = sizeof(XenLegacyDevice),
 };
 
 static void xen_sysbus_class_init(ObjectClass *klass, void *data)
@@ -672,7 +670,6 @@ static const TypeInfo xensysbus_info = {
 static const TypeInfo xensysdev_info = {
     .name          = TYPE_XENSYSDEV,
     .parent        = TYPE_SYS_BUS_DEVICE,
-    .instance_size = sizeof(SysBusDevice),
 };
 
 static void xenbe_register_types(void)

include/hw/xen/xen_pvdev.h

@@ -1,7 +1,7 @@
 #ifndef QEMU_HW_XEN_PVDEV_H
 #define QEMU_HW_XEN_PVDEV_H
 
-#include "hw/qdev-core.h"
+#include "hw/sysbus.h"
 #include "hw/xen/xen_backend_ops.h"
 
 /* ------------------------------------------------------------- */
@@ -32,7 +32,8 @@ struct XenDevOps {
 };
 
 struct XenLegacyDevice {
-    DeviceState        qdev;
+    SysBusDevice parent_obj;
+
     const char         *type;
     int                dom;
     int                dev;