On Thu, Jan 05, 2017 at 01:39:29PM -0500, Jerome Glisse wrote:
1) peer-to-peer because of userspace specific API like NVidia GPU
direct (AMD is pushing its own similar API i just can't remember
marketing name). This does not happen through a vma, this happens
through specific device driver call going through device specific
ioctl on both side (GPU and RDMA). So both kernel driver are aware
of each others.
Today you can only do user-initiated RDMA operations in conjection
with a VMA.
We'd need a really big and strong reason to create an entirely new
non-VMA based memory handle scheme for RDMA.
So my inclination is to just completely push back on this idea. You
need a VMA to do RMA.
GPUs need to create VMAs for the memory they want to RDMA from, even
if the VMA handle just causes SIGBUS for any CPU access.