> From: Jason Gunthorpe <jgg@xxxxxxxxxx> > Sent: Thursday, May 23, 2024 8:59 PM > On Thu, May 23, 2024 at 01:43:45AM +0000, Tian, Kevin wrote: > > > From: Jason Gunthorpe <jgg@xxxxxxxxxx> > > > Sent: Wednesday, May 22, 2024 9:39 PM > > > > > > The driver will then know it should program three different VMIDs for > > > the same S2 page table, which matches the ARM expectation for > > > VMID. That is to say we'd pass in the viommu as the pt_id for the > > > iommu_hwpt_alloc. The viommu would imply both the S2 page table and > > > any meta information like VMID the driver needs. > > > > Can you elaborate the aspect about "three different VMIDs"? > > In SMMUv3 the cache is tagged by (VMID,ASID) where ASID is completely > controlled by the guest. > > Every time the guest observes a SMMUv3 instance it is allowed to > creates its own private ASID number space for that instance. The guest > could re-use ASID #1 on two instances. > > So every SMMUv3 instance plugged into the guest needs to have its own > unique VMID so that the overlapping ASID's are disambiguate. The above > would create a VM where: > > deva -> vSMMUv3 #1 > devb -> vSMMUv3 #2 > devc -> No IOMMU This assumes that each vSMMUv3 instance has only one ASID space i.e. the guest cannot create multiple VMID's itself? > > > Hmm, given we currently have no known hardware entanglement > between > > > PRI and VIOMMU it does seem OK for PRI to just exist seperate for > > > > Isn't AMD vPPRLog for directly sending PRI request into the guest? > > I think it is, but that would be a vQUEUE on the VIOMMU not adding a > VIOMMU to Lu's patches, which is what I ment. > > > > now. If someone needs them linked someday we can add a viommu_id to > > > the create pri queue command. > > > > I'm more worried about the potential conflict between the vqueue > > object here and the fault queue object in Baolu's series, if we want > > to introduce vIOMMU concept to platforms which lack of the hw > > support. > > I assume the vPPRLog will steal all the PRI before it reaches the > kernel, so once this is turned on Lu's path won't see anything. > Okay, then we expect this vqueue object only for HW acceleration while software-based fault logging is still routed via Baolu's work.
