Re: [RFC v2] /dev/iommu uAPI proposal

David Gibson
2021-08-06T05:33:58Z

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On Wed, Aug 04, 2021 at 11:04:47AM -0300, Jason Gunthorpe wrote:
> On Mon, Aug 02, 2021 at 02:49:44AM +0000, Tian, Kevin wrote:
>
> > Can you elaborate? IMO the user only cares about the label (device cookie
> > plus optional vPASID) which is generated by itself when doing the attaching
> > call, and expects this virtual label being used in various spots (invalidation,
> > page fault, etc.). How the system labels the traffic (the physical RID or RID+
> > PASID) should be completely invisible to userspace.
>
> I don't think that is true if the vIOMMU driver is also emulating
> PASID. Presumably the same is true for other PASID-like schemes.

Right. The idea for an SVA capable vIOMMU in my scheme is that the
hypervisor would set up an IOAS of address type "PASID+address" with
the mappings made by the guest according to its vIOMMU semantics.
Then SVA capable devices would be plugged into that IOAS by using
"PASID+address" type endpoints from those devices.

--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson

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