On 26 October 2017 at 17:36, Jason A. Donenfeld <ja...@zx2c4.com> wrote: > On Thu, Oct 26, 2017 at 6:34 PM, Peter Maydell <peter.mayd...@linaro.org> > wrote: >> Reordering it would break existing users of the trustzone uart, >> whose command lines would stop working. > > I thought this was the reason for all of those virt26, virt28,etc > types -- people who want stability code the revision into their > scripts. Everybody else then gets the latest.
Those are primarily about migration compatibility -- you should be able to live migrate a guest from QEMU 2.6's virt-2.6 machine to QEMU 2.7's virt-2.6 machine. That's a stricter requirement than the compatibility we want to keep for non-versioned machines, where generally we don't want to break command lines but are OK to make changes if they don't break those existing uses. Command lines get baked into all sorts of scripts and so they're effectively part of QEMU's "ABI". People don't like it when we break their previously working flows :-) thanks -- PMM
