On Tue, Apr 18, 2017 at 3:46 PM, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> wrote: > On Tue, 2017-04-18 at 10:27 -0700, Dan Williams wrote: >> > FWIW, RDMA probably wouldn't want to use a p2mem device either, we >> > already have APIs that map BAR memory to user space, and would like to >> > keep using them. A 'enable P2P for bar' helper function sounds better >> > to me. >> >> ...and I think it's not a helper function as much as asking the bus >> provider "can these two device dma to each other". The "helper" is the >> dma api redirecting through a software-iommu that handles bus address >> translation differently than it would handle host memory dma mapping. > > Do we even need tat function ? The dma_ops have a dma_supported() > call... > > If we have those override ops built into the "dma_target" object, > then these things can make that decision knowing both the source > and target device. > Yes.
