Enabling peer to peer device transactions for PCIe devices

[Haggai Eran]

On 11/30/2016 8:01 PM, Logan Gunthorpe wrote:
> 
> 
> On 30/11/16 09:23 AM, Jason Gunthorpe wrote:
>>> Two cases I can think of are RDMA access to an NVMe device's controller
>>> memory buffer,
>>
>> I'm not sure on the use model there..
> 
> The NVMe fabrics stuff could probably make use of this. It's an
> in-kernel system to allow remote access to an NVMe device over RDMA. So
> they ought to be able to optimize their transfers by DMAing directly to
> the NVMe's CMB -- no userspace interface would be required but there
> would need some kernel infrastructure.

Yes, that's what I was thinking. The NVMe/f driver needs to map the CMB for
RDMA. I guess if it used ZONE_DEVICE like in the iopmem patches it would be
relatively easy to do.