Re: [PATCH v2 02/22] PCI: Add API to track PCI devices preserved across Live Update

[Jason Gunthorpe]

On Fri, Feb 27, 2026 at 02:35:42PM -0800, David Matlack wrote:
> > Live migration support, it's the primary use case currently where we
> > have vfio-pci variant drivers on VFs communicating with in-kernel PF
> > drivers.  Thanks,
> 
> I see so you're saying if those users wanted Live Update support and
> we didn't do (3), they would have to give up their Live Migration
> support. So that would be additional motivation to do (3).
> 
> Jason, does this change your mind about whether (3) is worth doing, or
> whether it should be prioritized over (2)?

No, not at all. Live migration of VFIO devices has turned into a
valuable but niche feature. This live update is a different niche
feature. I don't see an issue with making them exclusive as the
starting point.

I think people will eventually be interested in having live update as
an option on otherwise live migration capable hypervisors, but that
brings a whole other set of problems that are hard to solve..

> software with minimal impact to the VM. Live Update really shines in
> scenarios where Live Migraiton is untenable, since host upgrades
> require VM terminations. 

Yes, exactly. It is more important to bring a new capability than to
optimize something existing.

Jason