On Thu, Sep 13, 2012 at 07:14:08AM -0600, Eric Blake wrote: > On 09/13/2012 04:49 AM, Gleb Natapov wrote: > >> They do if you hibernate your laptop. > >> > > AFAIK libvirt migrates vm into a file on hibernate. It is better to move to > > S3 > > (using qemu-ga) instead and migrate to file only if s3 fails. > > On host hibernate, libvirt currently does nothing to the guest. When > the host resumes, the guests see a large gap in execution. > > Libvirt would need a hook into host hibernation, to have enough time to > tell the guests to go into S3 prior to allowing the host to go into S3. > > On host reboot, libvirt currently saves guests to disk using migrate to > file. The ideal solution would be to first tell the guest to go into S3 > before migrating to file, but the migration to file STILL must occur, > because the host is about to reboot and S3 is not persistent. S3 is a > better solution than S4, in that S4 requires the guest to have enough > memory (and if it doesn't cooperate, data is lost), but with S3, even if > the guest doesn't cooperate, we can still fall back to migration to file > with the guest only losing time, but not data.
Trying to hook into host S3/S4 and do magic to the guests is just asking for trouble. Not only can it arbitrarily delay the host going into S3/S4, but it is not reliable in general, even for OS which do support it. Much better off hooking into the resume path on the host and issuing a QEMU GA call to each running guest to resync their clocks Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
