Messages in this thread | | | From | "Campin, Mike" <> | Subject | RE: [RFC 0/7] Support in-kernel DMA with PASID and SVA | Date | Thu, 30 Sep 2021 14:22:34 +0000 |
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I need support for mixed user PASID, kernel PASID and non-PASID use cases in the driver.
-----Original Message----- From: Jason Gunthorpe <jgg@nvidia.com> Sent: Wednesday, September 29, 2021 4:43 PM To: Jacob Pan <jacob.jun.pan@linux.intel.com> Cc: iommu@lists.linux-foundation.org; LKML <linux-kernel@vger.kernel.org>; Joerg Roedel <joro@8bytes.org>; Christoph Hellwig <hch@infradead.org>; Tian, Kevin <kevin.tian@intel.com>; Luck, Tony <tony.luck@intel.com>; Jiang, Dave <dave.jiang@intel.com>; Raj, Ashok <ashok.raj@intel.com>; Kumar, Sanjay K <sanjay.k.kumar@intel.com>; Campin, Mike <mike.campin@intel.com>; Thomas Gleixner <tglx@linutronix.de> 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 <jgg@nvidia.com> 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
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