On Wed, Jun 17, 2015 at 01:53:11PM +0200, Paolo Bonzini wrote: > > > On 17/06/2015 13:45, 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. > > Paolo
If you change prog_if migration fails. -- MST