On Tue, Aug 20, 2024 at 09:01:02AM -0300, Jason Gunthorpe wrote: > Also bear in mind VFIO won't run unless ARM_SMMU_FEAT_COHERENCY is set > so we won't even get a chance to ask for a S2 domain. And I should also say that without iommufd something like the DMA API could select a S2 with S2FWB enabled, but all that does is change the encoding of the memattr bits. Requests for !IOMMU_CACHE will still map to non-cacheble IO PTEs like before - just with a different encoding. The only thing at issue is nesting which will end up in the guest as forced cachable - however since VFIO doesn't support non-DMA-coherent devices at all this is not a problem. Jason
