On Mon, Feb 11, 2019 at 12:34:47PM +0100, Marc-André Lureau wrote: > Hi > > On Mon, Feb 11, 2019 at 12:09 PM Daniel P. Berrangé <berra...@redhat.com> > wrote: > > > > On Fri, Feb 08, 2019 at 07:12:26PM +0100, Marc-André Lureau wrote: > > > Once libslirp has received its first release, we can link with the > > > external libslirp library. > > > > > > The migration data should be compatible with current and older qemu > > > versions (same compatibility as today). See "slirp: add state > > > saving/loading" patch. However, the content should be treated as a > > > blob, as the format may change eventually in the future. > > > > How are we going to manage live migration compat if libslirp changes > > the blob content ? > > > > Bear in mind that we need to support all existing QEMU releases live > > migrating to effectively all future QEMU releases, with all future > > libslirp releases, in *both* directions. ie arbitrarily newer > > libslirp needs to be able to emit a blob format that can be read > > by arbitrarily older slirp inside QEMU. > > > Right, this is all supported currently with the proposed patch set, > since it is effectively the same code. > > So register_savevm_live() get passed slirp_state_version() (currently == 4) > > & slirp_state_load() get the version_id from QEMU. > > > > > Normally we tie data format changes to the machine type. How are > > we going to achieve such machine type associations with an external > > libslirp ? > > Is this relevant for slirp? I don't see any version tied to machine > type. Am I missing something?
Old to new would work provided new slirp can read & understand all previous slirp state versions. It is entirely possible no one ever tested new -> old live migration with slirp. I doubt we would have tested it in RHEL, since we don't really care very much about slirp in context of migration. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
