On 10/08/18 10:02 AM, Kit Chow wrote: > Turns out there is no dma_map_resource routine on x86. get_dma_ops > returns intel_dma_ops which has map_resource pointing to NULL. Oh, yup. I wasn't aware of that. From a cursory view, it looks like it shouldn't be too hard to implement though. > Will poke around some in the intel_map_page code but can you actually > get a valid struct page for a pci bar address (dma_map_single calls > virt_to_page)? If not, does a map_resource routine that can properly > map a pci bar address need to be implemented? Yes, you can not get a struct page for a PCI bar address unless it's mapped with ZONE_DEVICE like in my p2p work. So that would explain why dma_map_single() didn't work. This all implies that ntb_transport doesn't work with DMA and the IOMMU turned on. I'm not sure I've ever tried that configuration myself but it is a bit surprising. Logan
