On Tue, Apr 23, 2024 at 07:43:27AM +0000, Tian, Kevin wrote: > I'm not sure how userspace can fully handle this w/o certain assistance > from the kernel. > > So I kind of agree that emulated PASID capability is probably the only > contract which the kernel should provide: > - mapped 1:1 at the physical location, or > - constructed at an offset according to DVSEC, or > - constructed at an offset according to a look-up table > > The VMM always scans the vfio pci config space to expose vPASID. > > Then the remaining open is what VMM could do when a VF supports > PASID but unfortunately it's not reported by vfio. W/o the capability > of inspecting the PASID state of PF, probably the only feasible option > is to maintain a look-up table in VMM itself and assumes the kernel > always enables the PASID cap on PF. I'm still not sure I like doing this in the kernel - we need to do the same sort of thing for ATS too, right? It feels simpler if the indicates if PASID and ATS can be supported and userspace builds the capability blocks. There are migration considerations too - the blocks need to be migrated over and end up in the same place as well.. Jason
