On Wed, Jun 01, 2022 at 12:15:47PM -0600, Alex Williamson wrote: > On Wed, 1 Jun 2022 14:30:54 -0300 > Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > > > On Wed, Jun 01, 2022 at 10:21:51AM -0600, Alex Williamson wrote: > > > > > Some ioctls clearly cannot occur while the device is in low power, such > > > as resets and interrupt control, but even less obvious things like > > > getting region info require device access. Migration also provides a > > > channel to device access. > > > > I wonder what power management means in a case like that. > > > > For the migration drivers they all rely on a PF driver that is not > > VFIO, so it should be impossible for power management to cause the PF > > to stop working. > > > > I would expect any sane design of power management for a VF to not > > cause any harm to the migration driver.. > > Is there even a significant benefit or use case for power management > for VFs? The existing D3hot support should be ok, but I imagine to > support D3cold, all the VFs and the PF would need to move to low power. > It might be safe to simply exclude VFs from providing this feature for > now. I know of no use case, I think it would be a good idea to exclude VFs. > Yes, but that's also penalizing devices that require no special > support, for the few that do. I'm not opposed to some sort of > vfio-pci-nvidia-gpu variant driver to provide that device specific > support, but I'd think the device table for such a driver might just be > added to the exclusion list for power management support in vfio-pci. > vfio-pci-core would need some way for drivers to opt-out/in for power > management. If you think it can be done generically with a small exclusion list then that probably makes sense. Jason
