On Mon, Aug 19, 2024 at 11:38:22AM -0700, Nicolin Chen wrote: > On Mon, Aug 19, 2024 at 03:28:11PM -0300, Jason Gunthorpe wrote: > > On Mon, Aug 19, 2024 at 11:19:39AM -0700, Nicolin Chen wrote: > > > > > > But nesting enablment with out viommu is alot less useful than I had > > > > thought :( > > > > > > Actually, without viommu, the hwpt cache invalidate alone could > > > still support non-SVA case? > > > > That is what I thought, but doesn't the guest still have to invalidate > > the CD table entry # 0? > > I recall it doesn't. The CD cache invalidation is required in the > viommu invalidation for an SVA case where we need a PASID number > to specify CD to the substream. But the CD to the default stream > is only changed during a vSTE setup, and the host knows the PASID > number (=0)? I think that would subtly assume certain things about how the driver does ordering, ie the that CD table entry 0 is setup with the S1 before we load it into the STE. Yes, the Linux driver does that now, but I don't think anyone should rely on that.. Jason
