Re: [PATCH 3/3] vfio: Report PASID capability via VFIO_DEVICE_FEATURE ioctl

Jason Gunthorpe
2023-12-12T15:27:32Z

On Mon, Dec 11, 2023 at 08:39:46PM -0700, Alex Williamson wrote:

> So how do we keep up with PCIe spec updates relative to the PASID
> capability with this proposal? Would it make more sense to report the
> raw capability register and capability version rather that a translated
> copy thereof? Perhaps just masking the fields we're currently prepared
> to expose.

I think the VMM must always create a cap based on the PCIe version it
understands. We don't know what future specs will put there so it
seems risky to forward it if we don't know that any possible
hypervisor support is present.

We have this problem on and off where stuff in PCI config space needs
explicit hypervisor support or it doesn't work in the VM and things
get confusing.

Jason