On Fri, Aug 10, 2007 at 12:36:05PM -0400, Jim Paris wrote: > Daniel Veillard wrote: > > On Thu, Aug 09, 2007 at 10:55:10PM +0100, Daniel P. Berrange wrote: > > > Just been committed to KVM repos I see. Should be an easy patch to backport > > > too. As long as we can detect failure if this is missing & report it back > > > then I'm fine depending on this. > > > > Would checking for the kvm version from the console sufficient ? Since KVM > > makes even more releases than libvirt in average I guess that would be > > fine. > > I'm not sure the kvm qemu binary even reports the kvm version > anywhere. I'll ask on kvm-devel to see if qemu/VERSION could get > updated with each KVM release. > > > > > - I append the domain's UUID at the end of the migration image. > > > > This doesn't affect KVM at all (it ignores the extra data). > > > > Does that seem reasonable? It's unclear how the saved image > > > > is supposed to get associated with a particular VM configuration > > > > without doing something like this. > > > > > > Actually I'd store the entire XML config appended to the end of the image. > > > Its quite possible the saved image may be restored on a different machine > > > so libvirt will need the XML config there & its not much work to automatically > > > append it all & use it when restoring later. > > > > +1 . The only problem is that the XML has no predefined size, so it may be > > hard to stack more stuff behind it. I would ask first on the KVM list to check > > if it's okay to add a variable lenght data structure at the end, they might > > want to extend it in the future and that would be hard to handle. > > I think appending unrelated data to the migration image is a bit of a > hack anyway. A better plan would be a file containing > <header> <XML config> <migration data> > > On save, libvirt writes <header> and <XML config>, then closes it and > uses "dd of=path oflag=append conv=notrunc" or just "cat >> path" as > the migration command. > > On restore, libvirt reads the header and XML config, and then > feeds the remaining migration data to KVM using "-incoming stdio". > I had wanted to avoid the trouble of feeding data via stdin, but > maybe a well placed dup2(fd,STDIN_FILENO) would do the trick > automatically. That sounds like a reasonable plan > This file format would also make it easier for e.g. virt-manager to > determine that a file is a valid libvirt restore image. A little magic in the first couple of bytes would be handy - thats what we check currently for Xen. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=| -- Libvir-list mailing list Libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list