On Wed, Sep 29, 2021 at 03:57:20PM -0700, Jacob Pan wrote: > Hi Jason, > > On Wed, 29 Sep 2021 16:39:53 -0300, Jason Gunthorpe <[email protected]> wrote: > > > On Wed, Sep 29, 2021 at 12:37:19PM -0700, Jacob Pan wrote: > > > > > For #2, it seems we can store the kernel PASID in struct device. This > > > will preserve the DMA API interface while making it PASID capable. > > > Essentially, each PASID capable device would have two special global > > > PASIDs: > > > - PASID 0 for DMA request w/o PASID, aka RID2PASID > > > - PASID 1 (randomly selected) for in-kernel DMA request w/ > > > PASID > > > > This seems reasonable, I had the same thought. Basically just have the > > driver issue some trivial call: > > pci_enable_pasid_dma(pdev, &pasid) > That would work, but I guess it needs to be an iommu_ call instead of pci_?
Which ever makes sense.. The API should take in a struct pci_device and return a PCI PASID - at least as a wrapper around a more generic immu api. > I think your suggestion is more precise, in case the driver does not want > to do DMA w/ PASID, we can do less IOTLB flush (PASID 0 only). Since it is odd, and it may create overhead, I would do it only when asked to do it > > Having multiple RID's pointing at the same IO page table is something > > we expect iommufd to require so the whole thing should ideally fall > > out naturally. > That would be the equivalent of attaching multiple devices to the same > IOMMU domain. right? Effectively.. Jason _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
