When this VMSD was introduced it's version fields were set to
sizeof(I6300State), making them essentially random from build to build,
version to version.
To fix this, we lock in a high version id and low minimum version id to
support old->new migration from all prior versions of this device's
state. This should work since the device state has not changed since
its introduction.
The potentially breaks migration from 1.5+ to 1.5, but since the
versioning was essentially random prior to this patch, new->old
migration was not consistently functional to begin with.
Reported-by: Nicholas Thomas <n...@bytemark.co.uk>
Suggested-by: Peter Maydell <peter.mayd...@linaro.org>
Cc: qemu-sta...@nongnu.org
Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com>
---
hw/watchdog/wdt_i6300esb.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/hw/watchdog/wdt_i6300esb.c b/hw/watchdog/wdt_i6300esb.c
index 1407fba..851b664 100644
--- a/hw/watchdog/wdt_i6300esb.c
+++ b/hw/watchdog/wdt_i6300esb.c
@@ -374,9 +374,22 @@ static const MemoryRegionOps i6300esb_ops = {
static const VMStateDescription vmstate_i6300esb = {
.name = "i6300esb_wdt",
- .version_id = sizeof(I6300State),
- .minimum_version_id = sizeof(I6300State),
- .minimum_version_id_old = sizeof(I6300State),
+ /* With this VMSD's introduction, version_id/minimum_version_id were
+ * erroneously set to sizeof(I6300State), causing a somewhat random
+ * version_id to be set for every build. This eventually broke
+ * migration.
+ *
+ * To correct this without breaking old->new migration for older versions
+ * of QEMU, we've set version_id to a value high enough to exceed all past
+ * values of sizeof(I6300State) across various build environments, and have
+ * reset minimum_version_id_old/minimum_version_id to 1, since this VMSD
+ * has never changed and thus can except all past versions.
+ *
+ * For future changes we can treat these values as we normally would.
+ */
+ .version_id = 10000,
+ .minimum_version_id = 1,
+ .minimum_version_id_old = 1,
.fields = (VMStateField []) {
VMSTATE_PCI_DEVICE(dev, I6300State),
VMSTATE_INT32(reboot_enabled, I6300State),
--
1.7.9.5
