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