> But it's easy to support migration to old qemu just > by discarding the INTx state, and this is not > at all harder, or worse, than migrating from old qemu > to new one.
Do we really care about migrating to older versions? Migrating to a new version (backward compatibility) I see the use, it allows people to do upgrades with minimal downtime. I have my reservations about how feasible this is long-term, but within a release series it's not too bad. However is migrating to an old version (forward compatibility) really a worthwhile thing to support? It sounds like the sort of thing that we're never really going to test properly, so will probably fail a good proportion of the time anyway. Reading in old state files is a whole lot easier (to write maintain, and stay sane) than producing state that is bug-compatible with previous versions. This feels something where the best answer all round is "Don't do that". Paul
