On Wed, Jun 17, 2015 at 01:03:00PM -0400, Don Slutz wrote: > On 06/17/15 12:29, Michael S. Tsirkin wrote: > > On Wed, Jun 17, 2015 at 06:17:19PM +0200, Paolo Bonzini wrote: > >> > >> > >> On 17/06/2015 16:29, Michael S. Tsirkin wrote: > >>> On Wed, Jun 17, 2015 at 04:27:13PM +0200, Paolo Bonzini wrote: > >>>> > >>>> > >>>> On 17/06/2015 16:18, Michael S. Tsirkin wrote: > >>>>>>> Yes, that's what was done for parallel and pcspk as well. There's no > >>>>>>> infrastructure to avoid it. > >>>>>>> > >>>>>>> Paolo > >>>>> How do you mean? We have multiple ways to keep devices > >>>>> compatible with old versions. > >>>>> Set a new property to skip the extra stuff. > >>>> > >>>> Not if the device didn't have a vmstate at all, unfortunately. > >>> > >>> Skip creating the device completely for old machine types. > >> > >> Which device? The vmstate is tied to the same device that has always > >> been created. > > > > Just disable the new functionality. Make it behave in > > a compatible way. > > > >> we enable this thing by default (why do we?) > > > > Sigh. There is a very simple way to add a device in qemu: let user > > request it with -device. If one does this, one gets to maintain the > > resulting mess without bothering with pc maintainers in any way. > > > > But of course, everyone implementing a new feature feels it's such a > > great thing, and completel zero risk, it must be part of the default > > machine. Guess what, one then gets to bother with versioning from day 0. > > > >>>>> this seems like a big deal ... > >>>> > >>>> The PC speaker device is also enabled by default. > >>> > >>> This is historical, isn't it? > >> > >> Yes, but it has broken 2.3->2.2 migration. > >> > >> Let's just stop fighting windmills. > >> > >> Paolo > > > > I don't see what you are saying. Suddenly guest visible > > changes within a machine type are ok? > > > > So we have a bug, need to fix it, preferably before piling up > > more features. The best way imho is for 2.4 to avoid > > this device unless requested explicitly. > > > > My take on this is that Michael would like me to have a vmport_rpc=on > option, just like vmport=on (which already exists). With a default of off. > > I have no problem adding it. > > -Don Slutz
I'd prefer -device instead. This way we don't need to deal with it in PC code at all. -- MST