On Wed, Jul 12, 2017 at 06:00:46PM +0200, Thomas Huth wrote: > On 12.07.2017 17:04, Daniel P. Berrange wrote: > > On Wed, Jul 12, 2017 at 10:22:33AM +0200, Thomas Huth wrote: > >> We don't want to carry along old machine types forever. If we are able to > >> remove the pc machines up to 0.13 one day for example, this would allow > >> us to eventually kill the code for rombar=0 (i.e. where QEMU copies ROM > >> BARs directly to low memory). Everything up to pc-1.2 is also known to > >> have issues with migration. So let's start with a deprecation message > >> for the old machine types so that the (hopefully) few users of these old > >> systems start switching over to newer machine types instead. > > > > I think we must document & agree on our support policy for machine > > types, before we start marking them as deprecated. eg please consider > > the following document before accepting this deprecation patch: > > > > https://lists.gnu.org/archive/html/qemu-devel/2017-07/msg00652.html > > > > Note in that proposal there, I say we do *not* go through trouble of > > explicitly marking machines as deprecated. We just document upfront > > the intended lifecycle and then delete them when it is done. > > > > Just use deprecation warnings for things where there is no predictable > > lifecycle upfront. > > I'm still not 100% sure whether that auto-deprecation of machine types > is such a good idea ... since we might need to maintain machines in > downstream a little bit longer than specified there, it might be better > to rather deprecate them manually from time to time.
Downstreams usually maintain custom machine types, so fact that the upstream machine types get deleted is not a problem in itself. The problem comes if followup internal code removal then prevents downstream from creating their custom machine type. I don't think we need tie these issues together. We can remove old machine types, without immediately removing features that our harm creation of downstream machine types. > Anyway, concerning my patch - I'll stop here and won't send another > version. There is too much bikeshed painting going on in this area for > my taste, and since I'm rather a powerpc / s390x guy, I'm also fine if > the pc-0.x machines stay around forever. If somebody else wants to push > this topic instead, feel free to do so. FWIW, I think your proposals have been very useful in general. It has been way overdue to have this kind of discussion. I just want us to focus on defining a policy, rather than making adhoc decisions each time around, as the later is rather unpredictable for users of qemu. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
