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.)