On Wed, Sep 16, 2020 at 11:21:10AM -0700, Jacob Pan (Jun) wrote: > Hi Jason, > On Wed, 16 Sep 2020 14:01:13 -0300, Jason Gunthorpe <jgg@xxxxxxxxxx> > wrote: > > > On Wed, Sep 16, 2020 at 09:33:43AM -0700, Raj, Ashok wrote: > > > On Wed, Sep 16, 2020 at 12:07:54PM -0300, Jason Gunthorpe wrote: > > > > On Tue, Sep 15, 2020 at 05:22:26PM -0700, Jacob Pan (Jun) wrote: > > > > > > If user space wants to bind page tables, create the PASID with > > > > > > /dev/sva, use ioctls there to setup the page table the way it > > > > > > wants, then pass the now configured PASID to a driver that > > > > > > can use it. > > > > > > > > > > Are we talking about bare metal SVA? > > > > > > > > What a weird term. > > > > > > Glad you noticed it at v7 :-) > > > > > > Any suggestions on something less weird than > > > Shared Virtual Addressing? There is a reason why we moved from SVM > > > to SVA. > > > > SVA is fine, what is "bare metal" supposed to mean? > > > What I meant here is sharing virtual address between DMA and host > process. This requires devices perform DMA request with PASID and use > IOMMU first level/stage 1 page tables. > This can be further divided into 1) user SVA 2) supervisor SVA (sharing > init_mm) > > My point is that /dev/sva is not useful here since the driver can > perform PASID allocation while doing SVA bind. No, you are thinking too small. Look at VDPA, it has a SVA uAPI. Some HW might use PASID for the SVA. When VDPA is used by DPDK it makes sense that the PASID will be SVA and 1:1 with the mm_struct. When VDPA is used by qemu it makes sense that the PASID will be an arbitary IOVA map constructed to be 1:1 with the guest vCPU physical map. /dev/sva allows a single uAPI to do this kind of setup, and qemu can support it while supporting a range of SVA kernel drivers. VDPA and vfio-mdev are obvious initial targets. *BOTH* are needed. In general any uAPI for PASID should have the option to use either the mm_struct SVA PASID *OR* a PASID from /dev/sva. It costs virtually nothing to implement this in the driver as PASID is just a number, and gives so much more flexability. > Yi can correct me but this set is is about VFIO-PCI, VFIO-mdev will be > introduced later. Last patch is: vfio/type1: Add vSVA support for IOMMU-backed mdevs So pretty hard to see how this is not about vfio-mdev, at least a little.. Jason
