Peter Xu <peterx@redhat.com> writes:
On Wed, Jul 10, 2024 at 01:21:51PM -0300, Fabiano Rosas wrote:
It's not about trust, we simply don't support migrations other than n->n+1 and (maybe) n->n-1. So QEMU from 2016 is certainly not included.
Where does it come from? I thought we suppport that..
I'm taking that from: docs/devel/migration/main.rst: "In general QEMU tries to maintain forward migration compatibility (i.e. migrating from QEMU n->n+1) and there are users who benefit from backward compatibility as well." But of course it doesn't say whether that comes with a transitive rule allowing n->n+2 migrations.
The same question would be: are we requesting an OpenStack cluster to always upgrade QEMU with +1 versions, otherwise migration will fail?
Will an OpenStack cluster be using upstream QEMU? If not, then that's a question for the distro. In a very practical sense, we're not requesting anything. We barely test n->n+1/n->n-1, even if we had a strong support statement I wouldn't be confident saying migration from QEMU 2.7 -> QEMU 9.1 should succeed.