I need support for mixed user PASID, kernel PASID and non-PASID use cases in the driver.
-----Original Message----- From: Jason Gunthorpe <[email protected]> Sent: Wednesday, September 29, 2021 4:43 PM To: Jacob Pan <[email protected]> Cc: [email protected]; LKML <[email protected]>; Joerg Roedel <[email protected]>; Christoph Hellwig <[email protected]>; Tian, Kevin <[email protected]>; Luck, Tony <[email protected]>; Jiang, Dave <[email protected]>; Raj, Ashok <[email protected]>; Kumar, Sanjay K <[email protected]>; Campin, Mike <[email protected]>; Thomas Gleixner <[email protected]> Subject: Re: [RFC 0/7] Support in-kernel DMA with PASID and SVA 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
