Re: [Qemu-devel] [PATCH] Migration compatibility for serial

[Paolo Bonzini]

On 17/06/2015 13:54, Michael S. Tsirkin wrote:
>>> > >> > Where, in the specific case of migration?
> > > Just look at hour compat flags.
> > > 
> > > For example (intentionally using serial here):
> > >         {\
> > >             .driver   = "pci-serial",\
> > >             .property = "prog_if",\
> > >             .value    = stringify(0),\
> > >         },\
> > >         {\
> > >             .driver   = "pci-serial-2x",\
> > >             .property = "prog_if",\
> > >             .value    = stringify(0),\
> > >         },\
> > >         {\
> > >             .driver   = "pci-serial-4x",\
> > >             .property = "prog_if",\
> > >             .value    = stringify(0),\
> > >         },\
> > > 
> > > apparently some clients check the specific prog if
> > > value, completely breaking if the value was incorrect.
> > > So we fixed it for new machine types but not old ones.
> > 
> > That has nothing to do with migration.
> 
> If you change prog_if migration fails.

No, it doesn't.  The guest misbehaves maybe, but the migration format is
not affected.

Paolo