On Wed, Feb 10, 2021 at 09:34:52AM -0400, Jason Gunthorpe wrote: > > I'm a bit confused about the change from v1 to v2, especially about > > how to inject module specific operations. From live migration p.o.v > > it may requires two hook points at least for some devices (e.g. i40e > > in original Yan's example): > > IMHO, it was too soon to give up on putting the vfio_device_ops in the > final driver- we should try to define a reasonable public/private > split of vfio_pci_device as is the norm in the kernel. No reason we > can't achieve that. > > > register a migration region and intercept guest writes to specific > > registers. [PATCH 4/9] demonstrates the former but not the latter > > (which is allowed in v1). > > And this is why, the ROI to wrapper every vfio op in a PCI op just to > keep vfio_pci_device completely private is poor :( Yes. If Alex has a strong preference to keep some values private a split between vfio_pci_device vfio_pci_device_priv might be doable, but it is somewhat silly. > > Then another question. Once we have this framework in place, do we > > mandate this approach for any vendor specific tweak or still allow > > doing it as vfio_pci_core extensions (such as igd and zdev in this > > series)? > > I would say no to any further vfio_pci_core extensions that are tied > to specific PCI devices. Things like zdev are platform features, they > are not tied to specific PCI devices Yes, ZDEV is just a special case of exposing extra information for any PCI device on s390. It does not fit any split up vfio_pci framework. In fact I wonder why it even has its own config option. > > vfio-mdev is just the channel to bring VFIO APIs through mdev core > > to underlying vendor specific mdev device driver, which is already > > granted flexibility to tweak whatever needs through mdev_parent_ops. > > This is the second thing, and it could just be deleted. The actual > final mdev driver can just use vfio_device_ops directly. The > redirection shim in vfio_mdev.c doesn't add value. Yes, that would simplify a lot of things.
