Il 21/02/2013 08:44, Paolo Bonzini ha scritto: > Il 20/02/2013 22:03, Anthony Liguori ha scritto: >> Paolo Bonzini <pbonz...@redhat.com> writes: >> >>> Il 20/02/2013 21:26, Anthony Liguori ha scritto: >>>> Cole Robinson <crobi...@redhat.com> writes: >>>> >>>>> This switch will turn on all the migration compat bits needed to >>>>> perform migration from qemu-kvm to qemu. It's just a stub for now. >>>>> >>>>> This compat will break incoming migration from qemu < 1.3, but for >>>>> distros where qemu-kvm was the only shipped package for years it's >>>>> not a big loss (and I don't know any way to avoid it). >>>>> >>>>> Signed-off-by: Cole Robinson <crobi...@redhat.com> >>>> >>>> This can't be a build time option. It's ugly and just reintroduces a fork. >>> >>> It is not a fork; it does not change the migration format of QEMU >>> itself, only the parsing of old VMState versions. The importance of the >>> fork will dwindle over time, as the distros EOL the releases that used >>> qemu-kvm. >> >> Once a distro enables CONFIG_QEMU_KVM, it must keep it enabled forever. >> So the distros will contineut o do CONFIG_QEMU_KVM whereas upstream does >> not set it. It's a fork all within the same tree. > > They will set it for a while. For example, F18 is the last Fedora > release that had qemu-kvm < 1.3.0. As soon as F18 goes end-of-life > (which is with F21), Fedora will not need to set the configure option > anymore. > > Of course other distros will keep it for years rather than months, but > the idea is the same. > >> What about having something processed by readconfig that wasn't disabled >> by -nodefaults? Then we could make it a runtime option, but that's >> configurable globally. Then the distros can choose the default value in >> the config file. >> >> At least then, we can write unit tests with the option at run time, >> don't need to sprinkle #ifdefs everywhere, etc. > > That would make sense, but it shouldn't block this patch. What would > happen otherwise is that distros (who care about migration > compatibility) will just patch their code without even the #ifdefs. > It's already happening, these patches are in F18.
Ping, where do we stand here? Shall we discuss it next Tuesday? Paolo