hw/ide/piix: Move registration of VMStateDescription to DeviceClass

The modern, declarative way to set up VM state handling is to assign to
DeviceClass::vmsd attribute.

There shouldn't be any change in behavior since dc->vmsd causes
vmstate_register_with_alias_id() to be called on the instance during
the instance init phase. vmstate_register() was also called during the
instance init phase which forwards to vmstate_register_with_alias_id()
internally. Checking the migration schema before and after this patch confirms:

before:
> qemu-system-x86_64 -S
> qemu > migrate -d exec:cat>before.mig

after:
> qemu-system-x86_64 -S
> qemu > migrate -d exec:cat>after.mig

> analyze-migration.py -d desc -f before.mig > before.json
> analyze-migration.py -d desc -f after.mig > after.json
> diff before.json after.json
-> empty

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Message-Id: <20230531211043.41724-8-shentey@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

hw/ide/piix.c

@@ -28,7 +28,6 @@
  */
 
 #include "qemu/osdep.h"
-#include "migration/vmstate.h"
 #include "qapi/error.h"
 #include "hw/pci/pci.h"
 #include "hw/ide/piix.h"
@@ -159,8 +158,6 @@ static void pci_piix_ide_realize(PCIDevice *dev, Error **errp)
     bmdma_setup_bar(d);
     pci_register_bar(dev, 4, PCI_BASE_ADDRESS_SPACE_IO, &d->bmdma_bar);
 
-    vmstate_register(VMSTATE_IF(dev), 0, &vmstate_ide_pci, d);
-
     for (unsigned i = 0; i < 2; i++) {
         if (!pci_piix_init_bus(d, i, errp)) {
             return;
@@ -186,6 +183,7 @@ static void piix3_ide_class_init(ObjectClass *klass, void *data)
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
 
     dc->reset = piix_ide_reset;
+    dc->vmsd = &vmstate_ide_pci;
     k->realize = pci_piix_ide_realize;
     k->exit = pci_piix_ide_exitfn;
     k->vendor_id = PCI_VENDOR_ID_INTEL;
@@ -208,6 +206,7 @@ static void piix4_ide_class_init(ObjectClass *klass, void *data)
     PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
 
     dc->reset = piix_ide_reset;
+    dc->vmsd = &vmstate_ide_pci;
     k->realize = pci_piix_ide_realize;
     k->exit = pci_piix_ide_exitfn;
     k->vendor_id = PCI_VENDOR_ID_INTEL;