------- Comment From [email protected] 2018-05-02 08:34 EDT------- After working with Greg, we found that migration of Ubuntu 16.04.4 guest from Ubuntu 16.04.4 P8 Host to ubuntu 18.04 P9 host works but we need to explicitly boot the guest in source with compat settings even on P8 host, ie
<cpu mode='host-model'> <model>power8</model> </cpu> As Greg stated, this is because Ubuntu 16.04.4 use older qemu (Qemu 2.5) that boots the guest in raw mode where as Ubuntu 18.04 use newer Qemu (Qemu 2.11) that boots the guest in architected mode, which means if the guest runs in raw mode, then migration is only supported between identical hosts and if it run in architected mode, the guest can be migrated to any host that also supports this architected mode. In our case we try to migrate from raw mode to architected mode that's why we have to give explicit compat setting is source so that respective qemu command will be formed with compat setting in target for migration to start. This is limitation we have from past and Greg would be working on it to fix. We can safely close this bug but with a proper documentation to make sure this limitation is known to the user. But still backward migration is broken, migrating back Ubuntu 16.04.4 guest from Ubuntu 18.04 P9 Host -> Ubuntu 16.04.4 P8 Host is broken because cpu model QEMU 2.5 (-cpu host,compat=power8) and QEMU 2.11 (-machine max-cpu-compat=power8) known for latest qemu is not compatible with older qemu. So this is a new issue with different root cause for which I would raise a separate bug. Thanks Greg. -- Bala -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1763468 Title: [Ubuntu 18.04] P8 compat mode migration fails for Ubuntu 16.04.4 P8 Guest from Ubuntu 16.04.4 P8 Host -> Ubuntu 18.04 P9 Host To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-power-systems/+bug/1763468/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
