On Wed, 3 Feb 2021 at 10:49, Dr. David Alan Gilbert <dgilb...@redhat.com> wrote: > > * Peter Maydell (peter.mayd...@linaro.org) wrote: > > On Wed, 3 Feb 2021 at 10:28, Dr. David Alan Gilbert <dgilb...@redhat.com> > > wrote: > > > > > > * Philippe Mathieu-Daudé (phi...@redhat.com) wrote: > > > > Cc'ing migration team and qemu-arm@ list. > > > > > > I'll have to leave the detail of that to the ARM peole; but from a > > > migration point of view I think we do want the 64 bit ARM migrations to > > > be stable now. Please tie incompatible changes to machine types. > > > > That is the intention, but because there's no upstream testing > > of migration compat, we never notice if we get it wrong. > > What is x86 doing to keep cross-version migration working ? > > I know there used to be some of our team running Avocado tests for > compatibility regularly, I'm not sure of the current status. > It's something we also do regularly around when we do downstream > releases, so we tend to catch them then, although even on x86 that > often turns out to be a bit late.
So downstream testing only? I think that unless we either (a) start doing migration-compat testing consistently upstream or (b) RedHat or some other downstream start testing and reporting compat issues to us for aarch64 as they do for x86-64, in practice we're just not going to have working migration compat despite our best intentions. (None of the issues Aaron raises were deliberate compat breaks -- they're all "we made a change we didn't think affected migration but it turns out that it does".) thanks -- PMM
