Messages in this thread | | | Date | Tue, 15 Mar 2022 14:05:07 -0300 | From | Jason Gunthorpe <> | Subject | Re: [PATCH v2 5/8] iommu: Add PASID support for DMA mapping API users |
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On Tue, Mar 15, 2022 at 09:31:35AM -0700, Jacob Pan wrote:
> > IMHO it is a device mis-design of IDXD to require all DMA be PASID > > tagged. Devices should be able to do DMA on their RID when the PCI
> IDXD can do DMA w/ RID, the PASID requirement is only for shared WQ where > ENQCMDS is used. ENQCMDS has the benefit of avoiding locking where work > submission is done from multiple CPUs. > Tony, Dave?
This is what I mean, it has an operating mode you want to use from the kernel driver that cannot do RID DMA. It is a HW mis-design, IMHO.
Something like PASID0 in the ENQCMDS should have triggered RID DMA.
> > In any case I think we are better to wait for an actual user for multi > > DMA API iommu_domains to come forward before we try to build an API > > for it. > > What would you recommend in the interim?
Oh, I mean this approach at a high level is fine - I was saying we shouldn't try to broaden it like Robin was suggesting without a driver that needs multiple iommu_domains for the DMA API.
Jason
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