hw/isa/piix4: Migrate Reset Control Register

When adding the Reset register in commit 5790b75 we
forgot to migrate it.

While it is possible a VM using the PIIX4 is migrated just
after requesting a system shutdown, it is very unlikely.
However when restoring a migrated VM, we might have the
RCR bit #4 set on the stack and when the VM resume it
directly shutdowns.

Add a post_load() migration handler and set the default
RCR value to 0 for earlier versions, assuming the VM was
not going to shutdown before migration.

Fixes: 5790b75 ("piix4: Add the Reset Control Register")
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20210324200334.729899-1-f4bug@amsat.org>

hw/isa/piix4.c

@@ -93,12 +93,25 @@ static void piix4_isa_reset(DeviceState *dev)
     pci_conf[0xae] = 0x00;
 }
 
+static int piix4_ide_post_load(void *opaque, int version_id)
+{
+    PIIX4State *s = opaque;
+
+    if (version_id == 2) {
+        s->rcr = 0;
+    }
+
+    return 0;
+}
+
 static const VMStateDescription vmstate_piix4 = {
     .name = "PIIX4",
-    .version_id = 2,
+    .version_id = 3,
     .minimum_version_id = 2,
+    .post_load = piix4_ide_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_PCI_DEVICE(dev, PIIX4State),
+        VMSTATE_UINT8_V(rcr, PIIX4State, 3),
         VMSTATE_END_OF_LIST()
     }
 };