On Tue, Mar 07, 2023 at 02:32:09PM -0800, Jacob Pan wrote: > Hi Jason, > > On Fri, 3 Mar 2023 09:15:45 -0400, Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > > > On Fri, Mar 03, 2023 at 05:57:41PM +0800, Baolu Lu wrote: > > > On 2023/3/3 17:32, Jean-Philippe Brucker wrote: > > > > > I suppose the common thing is reserving some kind of special > > > > > PASIDs. > > > > Are you planning to use RID_PASID != 0 in VT-d? Otherwise we could > > > > just communicate min_pasid from the IOMMU driver the same way we do > > > > max_pasid. > > > > > > > > Otherwise I guess re-introduce a lighter ioasid_alloc() that the IOMMU > > > > driver calls to reserve PASID0/RID_PASID. > > > > > > Yes. We probably will use a non-zero RID_PASID in the future. An > > > interface to reserve (or allocate) a PASID from iommu_global_pasid_ida > > > should work then. > > > > Just allowing the driver to store XA_ZERO_ENTRY would be fine > > > It looks like there are incoming users of iommu_sva_find() > https://lore.kernel.org/lkml/20230306163138.587484-1-fenghua.yu@xxxxxxxxx/T/#m1fc97725a0e56ea269c8bdabacee447070d51846 > Should we keep the xa here instead of the global ida? I'm not sure this should be in the iommu core, it is really gross. I would expect IDXD to keep track of the PASID's and mms it is using and do this kind of stuff itself. And why is this using access_remote_vm anyhow? If you know you are in a kthread then kthread_use_mm() is probably better anyhow. In any event we don't need a iommu_sva_find() function to wrapper xa_load for another function inside the same .c file. Jason
