I can't really comment on the dma-ranges exlcusion for P2P mappings, as that predates my involvedment, however: On Wed, Apr 20, 2022 at 11:32:07AM +0300, Serge Semin wrote: > See, if I get to map a virtual memory address to be accessible by any > PCIe peripheral device, then the dma_map_sg/dma_map_page/etc > procedures will take the PCIe host controller dma-ranges into account. > It will work as expected and the PCIe devices will see the memory what > I specified. But if I get to pass the physical address of the same > page or a physical address of some device of the DEVs space to the > dma_map_resource(), then the PCIe dma-ranges won't be taken into > account, and the result mapping will be incorrect. That's why the > current dma_map_resource() implementation seems very confusing to me. > As I see it phys_addr_t is the type of the Interconnect address space, > meanwhile dma_addr_t describes the PCIe, DEVs address spaces. > > Based on what I said here and in my previous email could you explain > what do I get wrong? You simply must not use dma_map_resource for normal kernel memory. So while the exclusion might be somewhat confusing, that confusion really should not matter for any proper use of the API.
