On 2/3/21 11:59 AM, Dr. David Alan Gilbert wrote: > * Peter Maydell (peter.mayd...@linaro.org) wrote: >> 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 thought there used to be some regular avocado testing of upstream but > I'm not sure if it's all architectures and I'm not sure if it's still > happening; I haven't seen any migration issues from it for a while, > which makes me think it isn't. > >> 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".) > > I'd agree; we still hit this too often on x86 as well.
Cc'ing avocado-devel, since previously discussed: https://www.mail-archive.com/qemu-devel@nongnu.org/msg654139.html