Re: [PATCH v2 3/8] iommu/vt-d: Implement device_pasid domain attach ops

Jason Gunthorpe
2022-03-17T00:04:17Z

On Wed, Mar 16, 2022 at 10:23:26PM +0000, Luck, Tony wrote:

> Kernel users (ring0) can supply any PASID when they use
> the ENQCMDS instruction. Is that what you mean when you
> say "real applications"?

I'm not talking about ENQCMD at all

I'm saying I don't see much utility to have two PASIDs assigned to the
same device that perform the same IOVA translation.

So I would expect the list of attachments in an iommu_domain to have
exactly one device in it and multiple PASIDs to the same device from
the same iommu_domain is a oddball corner case we don't need to
optimize for, beyond being able to allow it to happen.

Jason