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