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From:   "Tian, Kevin" <kevin.tian@intel.com>
To:     Jason Gunthorpe <jgg@nvidia.com>
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Subject: RE: [RFC] /dev/ioasid uAPI proposal
Thread-Topic: [RFC] /dev/ioasid uAPI proposal
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Date:   Fri, 4 Jun 2021 06:37:26 +0000
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> From: Jason Gunthorpe
> Sent: Thursday, June 3, 2021 9:05 PM
>=20
> > >
> > > 3) Device accepts any PASIDs from the guest. No
> > >    vPASID/pPASID translation is possible. (classic vfio_pci)
> > > 4) Device accepts any PASID from the guest and has an
> > >    internal vPASID/pPASID translation (enhanced vfio_pci)
> >
> > what is enhanced vfio_pci? In my writing this is for mdev
> > which doesn't support ENQCMD
>=20
> This is a vfio_pci that mediates some element of the device interface
> to communicate the vPASID/pPASID table to the device, using Max's
> series for vfio_pci drivers to inject itself into VFIO.
>=20
> For instance a device might send a message through the PF that the VF
> has a certain vPASID/pPASID translation table. This would be useful
> for devices that cannot use ENQCMD but still want to support migration
> and thus need vPASID.

I still don't quite get. If it's a PCI device why is PASID translation requ=
ired?
Just delegate the per-RID PASID space to user as type-3 then migrating the=
=20
vPASID space is just straightforward.=20

Thanks
Kevin