mdroth <mdr...@linux.vnet.ibm.com> writes:
> On Tue, May 21, 2013 at 05:32:57PM -0500, Michael Roth wrote:
>> 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>
>
> CC'ing qemu-trivial. Looking to get this in for 1.5.1
v2? There were some review comments that haven't been addressed.
Regards,
Anthony Liguori
>
>> ---
>> 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
>>
