Re: [PATCH 3/4] iommu/vt-d: Support PASID DMA for in-kernel usage

[Jason Gunthorpe]

On Fri, Dec 10, 2021 at 10:18:20AM -0800, Jacob Pan wrote:

> > If one device has 10 PASID's pointing to this domain you must flush
> > them all if that is what the HW requires.
> > 
> Yes. My point is that other than PASID 0 is a given, we must track the 10
> PASIDs to avoid wasted flush. It also depend on how TLBs are tagged and
> flush granularity available. But at the API level, should we support all the
> cases?

Yes, iommufd will expose all the cases to userspace and anything is
possible.

A scheme that can only attach a domain to one PASID is functionally
useless except for this IDXD problem, so don't make something so
broken.

Jason