Re: Plan for /dev/ioasid RFC v2

David Gibson
2021-06-24T04:53:27Z

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On Thu, Jun 17, 2021 at 08:04:38PM -0300, Jason Gunthorpe wrote:
> On Thu, Jun 17, 2021 at 03:02:33PM +1000, David Gibson wrote:
>
> > In other words, do we really have use cases where we need to identify
> > different devices IDs, even though we know they're not isolated.
>
> I think when PASID is added in and all the complexity that brings, it
> does become more important, yes.
>
> At the minimum we should scope the complexity.
>
> I'm not convinced it is so complicated, really it is just a single bit
> of information toward userspace: 'all devices in this group must use
> the same IOASID'

Um.. no? You could have devA and devB sharing a RID, but then also
sharing a group but not a RID with devC because of different isolation
issues. So you now have (at least) two levels of group structure to
expose somehow.

>
> Something like qemu consumes this bit and creates the pci/pcie bridge
> to model this to the guest and so on.
>
> Something like dpdk just doesn't care (same as today).
>
> Jason
>

--
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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