On Thu, Apr 16, 2020 at 09:02:51PM +0000, Xiong, Jianxin wrote: > > > > > > Right, the GPU driver needs to cooperate to get the thing to work as > > > expected. The "p2p" flag and related GPU driver changes proposed in > > > other threads would ensure VRAM is really used. Alternatively, a GPU > > > driver can have a working mode that assumes p2p mapping capability of > > > the client. Either way, the patches to the RDMA driver would be mostly > > > identical except for adding the use of the "p2p" > > > flag. > > > > I think the other thread has explained this would not be "mostly identical" but here is significant work to rip out the scatter list from the > > umem. > > > > Probably we are referring to different threads here. Could you > kindly refer me to the thread you mentioned? I was referring to the > thread about patching dma-buf and GPU driver: > https://www.spinics.net/lists/amd-gfx/msg47022.html https://lore.kernel.org/linux-media/20200311152838.GA24280@xxxxxxxxxxxxx/ > > So, I'm back to my original ask, can you justify adding this if it > > cannot do VRAM? What is the use case? > > Working with VRAM is the goal. This patch has been tested with a > modified GPU driver that has dma_buf_ops set up to not migrate the > buffer to system memory when attached. The GPU drivers and the RDMA > drivers can be improved independently and it doesn't hurt to have > the RDMA driver ready before the GPU drivers. Well, if there is no other use case then this series will have to wait until someone does all the other work to make P2P work upstream. Jason
