On (Mon) 27 Jun 2016 [09:54:24], Paolo Bonzini wrote:
>
>
> On 27/06/2016 09:20, Amit Shah wrote:
> > On (Mon) 20 Jun 2016 [16:33:26], Paolo Bonzini wrote:
> >> Commit 926cde5 ("scsi: esp: make cmdbuf big enough for maximum CDB size",
> >> 2016-06-16) changed the size of a migrated field. Split it in two
> >> parts, and only migrate the second part in a new vmstate version.
> >
> > With this patch, the static checker fails in this way:
> >
> > Section "esp", Description "esp": expected field "cmdlen", got "cmdbuf";
> > skipping rest
> > Section "dc390", Description "esp": expected field "cmdlen", got "cmdbuf";
> > skipping rest
> > Section "am53c974", Description "esp": expected field "cmdlen", got
> > "cmdbuf"; skipping rest
> >
> > Note it doesn't complain about the version numbers. That's because:
> >
> >> const VMStateDescription vmstate_esp = {
> >> .name ="esp",
> >> - .version_id = 3,
> >> + .version_id = 4,
> >> .minimum_version_id = 3,
> >
> > this suggests older versions can still be accepted for incoming
> > migration, which isn't true.
>
> Sure they can:
>
> - VMSTATE_BUFFER(cmdbuf, ESPState),
> + VMSTATE_PARTIAL_BUFFER(cmdbuf, ESPState, 16),
> + VMSTATE_BUFFER_START_MIDDLE_V(cmdbuf, ESPState, 16, 4),
>
> 2.6 is transmitting version 3 and a 16-byte buffer.
>
> 2.7 is transmitting version 4, a first 16-byte buffer, and a second
> 16-byte buffer that is skipped when receiving version 3.
Hm, yeah.
> So it seems like a static checker limitation.
Yeah, so I think this can't be checked statically -- let me dig more.
Amit
