Re: [PATCH v5 01/13] PCI/P2PDMA: Support peer-to-peer memory

On 31/08/18 02:04 AM, Christian König wrote:

Am 30.08.2018 um 20:53 schrieb Logan Gunthorpe:

quoted

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