Re: [Qemu-devel] [PATCH v2] wdt_i6300esb: fix vmstate versioning

[Juan Quintela <quintela@redhat.com>]

mdroth <mdroth@linux.vnet.ibm.com> wrote:
> On Tue, Jun 11, 2013 at 04:53:51PM -0500, mdroth wrote:
>> On Wed, May 22, 2013 at 11:32:51AM -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 <nick@bytemark.co.uk>
>> > Suggested-by: Peter Maydell <peter.maydell@linaro.org>
>> > Cc: qemu-stable@nongnu.org
>> > Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
>> 
>> Ping, looking to pull this in for 1.5.1
>
> Anthony, Juan? Not sure if this is on your radar. Looking to get it
> applied prior to stable freeze tomorrow.

Reviewed-by: Juan Quintela <quintela@redhat.com>

I guess that the value was already there,  not that the version field
hasn't been abused lot of times.  I agree that sizeof() makes for an
interesting version number,  especially if padding enter the equation.