On Fri, Jan 18, 2019 at 10:16:34AM +0000, Dr. David Alan Gilbert wrote: > * Paolo Bonzini (pbonz...@redhat.com) wrote: > > On 18/01/19 11:02, Dr. David Alan Gilbert wrote: > > >> > > >> It fails if the flag is set, rather than if any nested virtualization has > > >> been used before. > > >> > > >> I'm concerned I will end up with a requirement for *all* guests to be > > >> restarted in order to migrate them to the new hosts, rather than just the > > >> ones that would have a problem. > > > I think you should be able to migrate from 2.12->3.1 like this, but > > > you'd hit the problem when you then try and migrate again between your > > > new QEMUs. > > > > > > I guess we could modify it to wire it to machine type, so that > > > older machine types didn't block. > > > > That would also be wrong. The old machine types _could_ be using KVM > > and they have no way to block the live migration. > > > > The solution is to restart the VM using "-cpu host,-vmx". > > The problem as Christian explained in that thread is that it was common > for them to start VMs with vmx enabled but for people not to use it > on most of the VMs, so we break migration for most VMs even though most > don't use it. > > It might not be robust, but it worked for a lot of people most of the > time.
Yes, this is exactly why I said we should make the migration blocker be conditional on any L2 guest having been started. I vaguely recall someone saying there wasn't any way to detect this situation from QEMU though ? 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 :|
