Hi Jean-Philippe, On Mon, 22 Mar 2021 10:24:00 +0100, Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx> wrote: > On Fri, Mar 19, 2021 at 11:22:21AM -0700, Jacob Pan wrote: > > Hi Jason, > > > > On Fri, 19 Mar 2021 10:54:32 -0300, Jason Gunthorpe <jgg@xxxxxxxxxx> > > wrote: > > > On Fri, Mar 19, 2021 at 02:41:32PM +0100, Jean-Philippe Brucker > > > wrote: > > > > On Fri, Mar 19, 2021 at 09:46:45AM -0300, Jason Gunthorpe wrote: > > > > > On Fri, Mar 19, 2021 at 10:58:41AM +0100, Jean-Philippe Brucker > > > > > wrote: > > > > > > Although there is no use for it at the moment (only two upstream > > > > > > users and it looks like amdkfd always uses current too), I quite > > > > > > like the client-server model where the privileged process does > > > > > > bind() and programs the hardware queue on behalf of the client > > > > > > process. > > > > > > > > > > This creates a lot complexity, how do does process A get a secure > > > > > reference to B? How does it access the memory in B to setup the > > > > > HW? > > > > > > > > mm_access() for example, and passing addresses via IPC > > > > > > I'd rather the source process establish its own PASID and then pass > > > the rights to use it to some other process via FD passing than try to > > > go the other way. There are lots of security questions with something > > > like mm_access. > > > > > > > Thank you all for the input, it sounds like we are OK to remove mm > > argument from iommu_sva_bind_device() and iommu_sva_alloc_pasid() for > > now? > > Fine by me. By the way the IDXD currently missues the bind API for > supervisor PASID, and the drvdata parameter isn't otherwise used. This > would be a good occasion to clean both. The new bind prototype could be: > > struct iommu_sva *iommu_sva_bind_device(struct device *dev, int flags) > yes, we really just hijacked drvdata as flags, it would be cleaner to use flags explicitly. > And a flag IOMMU_SVA_BIND_SUPERVISOR (not that I plan to implement it in > the SMMU, but I think we need to clean the current usage) > You mean move #define SVM_FLAG_SUPERVISOR_MODE out of Intel code to be a generic flag in iommu-sva-lib.h called IOMMU_SVA_BIND_SUPERVISOR? I agree if that is the proposal. > > > > Let me try to summarize PASID allocation as below: > > > > Interfaces | Usage | Limit | bind¹ |User visible > > -------------------------------------------------------------------- > > /dev/ioasid² | G-SVA/IOVA | cgroup | No > > |Yes > > -------------------------------------------------------------------- > > char dev³ | SVA | cgroup | Yes |No > > -------------------------------------------------------------------- > > iommu driver | default PASID| no | No |No > > > > Is this PASID #0? > True for native case but not limited to PASID#0 for guest case. E.g. for mdev assignment with guest IOVA, the guest PASID would #0, but the host aux domain default PASID can be non-zero. Here I meant to include both cases. > > -------------------------------------------------------------------- > > kernel | super SVA | no | yes |No > > -------------------------------------------------------------------- > > Also wondering about device driver allocating auxiliary domains for their > private use, to do iommu_map/unmap on private PASIDs (a clean replacement > to super SVA, for example). Would that go through the same path as > /dev/ioasid and use the cgroup of current task? > For the in-kernel private use, I don't think we should restrict based on cgroup, since there is no affinity to user processes. I also think the PASID allocation should just use kernel API instead of /dev/ioasid. Why would user space need to know the actual PASID # for device private domains? Maybe I missed your idea? > Thanks, > Jean > > > > > ¹ Allocated during SVA bind > > ² PASIDs allocated via /dev/ioasid are not bound to any mm. But its > > ownership is assigned to the process that does the allocation. > > ³ Include uacce, other private device driver char dev such as idxd > > > > Currently, the proposed /dev/ioasid interface does not map individual > > PASID with an FD. The FD is at the ioasid_set granularity and bond to > > the current mm. We could extend the IOCTLs to cover individual PASID-FD > > passing case when use cases arise. Would this work? > > > > Thanks, > > > > Jacob Thanks, Jacob
