> > > 5) iommufd and kvm are both using CPU addresses without DMA. No > > > exporter mapping is possible > > > > We have customers using both KVM and XEN with DMA-buf, so I can clearly > > confirm that this isn't true. > > Today they are mmaping the dma-buf into a VMA and then using KVM's > follow_pfn() flow to extract the CPU pfn from the PTE. Any mmapable > dma-buf must have a CPU PFN. Yes, the final target for KVM is still the CPU PFN, just with the help of CPU mapping table. I also found the xen gntdev-dmabuf is calculating pfn from mapped sgt.
