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From:   "Tian, Kevin" <kevin.tian@intel.com>
To:     David Gibson <david@gibson.dropbear.id.au>,
        Jason Gunthorpe <jgg@nvidia.com>
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        "Alexey Kardashevskiy" <aik@ozlabs.ru>
Subject: RE: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation
 APIs
Thread-Topic: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and
 allocation APIs
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Date:   Thu, 13 May 2021 06:52:43 +0000
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> From: David Gibson <david@gibson.dropbear.id.au>
> Sent: Thursday, May 13, 2021 2:01 PM
> >
> > But this definitely all becomes HW specific.
> >
> > For instance I want to have an ARM vIOMMU driver it needs to do some
> >
> >  ret =3D ioctl(ioasid_fd, CREATE_NESTED_IOASID, [page table format is
> ARMvXXX])
> >  if (ret =3D=3D -EOPNOTSUPP)
> >      ret =3D ioctl(ioasid_fd, CREATE_NORMAL_IOASID, ..)
> >      // and do completely different and more expensive emulation
> >
> > I can get a little bit of generality, but at the end of the day the
> > IOMMU must create a specific HW layout of the nested page table, if it
> > can't, it can't.
>=20
> Erm.. I don't really know how your IOASID interface works here.  I'm
> thinking about the VFIO interface where maps and unmaps are via
> explicit ioctl()s, which provides an obvious point to do translation
> between page table formats.
>=20

We are working on a draft uAPI proposal based on the discussions in this
thread. expect to send it out next week.=20

Thanks
Kevin