On Mon, Dec 01, 2025 at 12:50:24PM +0000, Chalios, Babis wrote: > Latest specification of VMClock[1] adds support for VM generation counter > and notifications. VM generation counter is similar to disruption_marker > but it only changes when the guest has been loaded from a snapshot, not > on live migration. Its purpose is to notify the guest about snapshot > events and let it perform actions such as recreating UUIDs, resetting > network connections, reseeding entropy, etc. > > Moreover, the spec now describes a notification that the device can send > after updating the seq counter to a new even number. > > I have already sent the Linux changes to the mailing list here: > https://lore.kernel.org/lkml/[email protected]/T/#u > > [1] https://david.woodhou.se/VMClock.pdf
Should that spec document the expected behaviour of guests when a hypervisor advertizes both vmclock and vmgenid devices ? QEMU supports both, and to avoid assumptions about whether a guest supports the newer vmclock, I could expect mgmt apps to expose both these QEMU devices. IIUC, your intent is that 'vmclock' obsoletes the need for 'vmgenid', so should the spec say that explicitly, and suggest that guest kernels ignore the vmgenid if both are present, to avoid the same kind of actions being triggered twice ? With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
