RE: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation APIs

Tian, Kevin
2021-05-08T05:46:19Z

> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Thursday, April 29, 2021 4:46 AM
>
> > > I think the name IOASID is fine for the uAPI, the kernel version can
> > > be called ioasid_id or something.
> >
> > ioasid is already an id and then ioasid_id just adds confusion. Another
> > point is that ioasid is currently used to represent both PCI PASID and
> > ARM substream ID in the kernel. It implies that if we want to separate
> > ioasid and pasid in the uAPI the 'pasid' also needs to be replaced with
> > another general term usable for substream ID. Are we making the
> > terms too confusing here?
>
> This is why I also am not so sure about exposing the PASID in the API
> because it is ultimately a HW specific item.
>
> As I said to David, one avenue is to have some generic uAPI that is
> very general and keep all this deeply detailed stuff, that really only
> matters for qemu, as part of a more HW specific vIOMMU driver
> interface.
>

OK, so the general uAPI will not expose hw_id and just provide everything
generic for managing I/O page table (map/unmap, nesting, etc.) through
IOASID and then specific uAPI is provided to handle platform specific
requirements (hw_id, iova windows, etc.)

Thanks
Kevin