On Wed, Sep 10, 2008 at 02:11:56PM +0300, Avi Kivity wrote: > Daniel P. Berrange wrote: > > >>This means that migration is no longer transparent. While migration is > >>going on, you can't change the cdrom media, look at cpu registers, or do > >>anything that requires the monitor. > >> > > > >Changing cdrom media while in the middle of migration sounds like a rather > >troubleprone thing todo - you'd need to change the media in both active > >QEMU instances at the same time to be safe. > > Or rather, such state should be part of the migration. There's the > question of whether to transform the path on the target, but "which > media is in the drive" is part of the hardware state. > > (logically we would copy all of the data of all block devices, but > that's not very practical, so we assume shared storage). > > What other commands are unsafe during migration? I exclude host device > assignment which is obviously migration unfriendly.
USB + virtio device attach/detach - well at least have the same need as media change - you'd need to propagate the change to the other side in some way. Currently migrate just assumes the management tool/admin has started QEMU on the destinations with the matching hardware config, and for libvirt to use the monitor to add USB /virtio devices at both ends has the race condition/synchronization problem . Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :| -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html