On 31/08/18 02:04 AM, Christian König wrote: > Am 30.08.2018 um 20:53 schrieb Logan Gunthorpe: >> Some PCI devices may have memory mapped in a BAR space that's >> intended for use in peer-to-peer transactions. In order to enable >> such transactions the memory must be registered with ZONE_DEVICE pages >> so it can be used by DMA interfaces in existing drivers. > > We want to use that feature without ZONE_DEVICE pages for DMA-buf as well. > > How hard would it be to separate enabling P2P detection (e.g. distance > between two devices) from this? Pretty easy. P2P detection is pretty much just pci_p2pdma_distance() , which has nothing to do with the ZONE_DEVICE support. (And the distance function makes use of a number of static functions which could be combined into a simpler interface, should we need it.) Logan
