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 > So we provide APIs for both? 1. alloc a global PASID, returned by this API 2. try to reserve a global PASID given by the driver, i.e. xa_cmpxchg(&iommu_global_pasid_ida.xa, 2, NULL, XA_ZERO_ENTRY, GFP_KERNEL); seems #1 is sufficient. Thanks, Jacob
