macfb: add VMStateDescription for MacfbNubusState and MacfbSysBusState

Currently when QEMU tries to migrate the macfb framebuffer it crashes randomly
because the opaque provided by the DeviceClass vmsd property for both devices
is set to MacfbState rather than MacfbNubusState or MacfbSysBusState as
appropriate.

Resolve the issue by adding new VMStateDescriptions for MacfbNubusState and
MacfbSysBusState which embed the existing vmstate_macfb VMStateDescription
within them using VMSTATE_STRUCT.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20220305155530.9265-2-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

hw/display/macfb.c

@@ -746,6 +746,16 @@ static Property macfb_sysbus_properties[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+static const VMStateDescription vmstate_macfb_sysbus = {
+    .name = "macfb-sysbus",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_STRUCT(macfb, MacfbSysBusState, 1, vmstate_macfb, MacfbState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static Property macfb_nubus_properties[] = {
     DEFINE_PROP_UINT32("width", MacfbNubusState, macfb.width, 640),
     DEFINE_PROP_UINT32("height", MacfbNubusState, macfb.height, 480),
@@ -755,14 +765,24 @@ static Property macfb_nubus_properties[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+static const VMStateDescription vmstate_macfb_nubus = {
+    .name = "macfb-nubus",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_STRUCT(macfb, MacfbNubusState, 1, vmstate_macfb, MacfbState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static void macfb_sysbus_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->realize = macfb_sysbus_realize;
     dc->desc = "SysBus Macintosh framebuffer";
     dc->reset = macfb_sysbus_reset;
-    dc->vmsd = &vmstate_macfb;
+    dc->vmsd = &vmstate_macfb_sysbus;
     device_class_set_props(dc, macfb_sysbus_properties);
 }
 
@@ -777,7 +797,7 @@ static void macfb_nubus_class_init(ObjectClass *klass, void *data)
                                       &ndc->parent_unrealize);
     dc->desc = "Nubus Macintosh framebuffer";
     dc->reset = macfb_nubus_reset;
-    dc->vmsd = &vmstate_macfb;
+    dc->vmsd = &vmstate_macfb_nubus;
     set_bit(DEVICE_CATEGORY_DISPLAY, dc->categories);
     device_class_set_props(dc, macfb_nubus_properties);
 }