[Hypervisor Live Update] Notes from May 19, 2025

[Pasha Tatashin]

On Mon, Jun 2, 2025 at 9:11 AM Jason Gunthorpe <jgg at nvidia.com> wrote:
>
> On Sat, May 31, 2025 at 08:16:14PM -0700, David Rientjes wrote:
> > Pratyush asked about the relationship between KHO and LUO.  Pasha noted
> > that KHO provides a state machine and in RFC v2 of LUO, LUO can drive KHO
> > which makes the KHO debugfs interface optional.  KHO activate will cause
> > LUO to switch to the prepared phase, for example.  /dev/liveupdate
> > continues to be the preferred mechanism.  Think of KHO as preserving state
> > across kexec whereas LUO provides the state machine.
>
> IMHO LUO should superceed the statemachine in KHO and it's
> debugfs. Just remove all the KHO stuff here. We don't need two things..

I agree, these two patches [1] [2] make KHO debugfs optional. I think
it is reasonable to keep KHO debugfs interface optionally available
for selftests, debugging, and development purposes. I do not think it
will be needed in production.

[1] https://lore.kernel.org/all/20250515182322.117840-2-pasha.tatashin@soleen.com/
[2] https://lore.kernel.org/all/20250515182322.117840-3-pasha.tatashin@soleen.com/

Pasha