> > I meant software wise. You're not going to live migrate from xen to > > kvm or backwards. or between very radically different versions of the > > kvm stack. > > Forwards migration to a radically newer version certainly happens. So > when the source hypervisor was too old to tell the VM about IBRS_ALL, > for example, migration should work properly and the VM should perform > well on the destination hypervisor. that makes sense, compatibility in this direction can be done and is useful as you move a fleet of servers forward > > Backwards migration to older hypervisors also happens sometimes, but in > general it creates more userspace than kernel issues. > that direction is obviously harder
