Re: [PATCH v4 29/32] vfio-pci/zdev: add DTSM to clp group capability

[Jason Gunthorpe]

On Mon, Mar 14, 2022 at 03:44:48PM -0400, Matthew Rosato wrote:
> The DTSM, or designation type supported mask, indicates what IOAT formats
> are available to the guest.  For an interpreted device, userspace will not
> know what format(s) the IOAT assist supports, so pass it via the
> capability chain.  Since the value belongs to the Query PCI Function Group
> clp, let's extend the existing capability with a new version.

Why is this on the VFIO device?

Maybe I don't quite understand it right, but the IOAT is the
'userspace page table'?

That is something that should be modeled as a nested iommu domain.

Querying the formats and any control logic for this should be on the
iommu side not built into VFIO.

Jason