Re: Enabling peer to peer device transactions for PCIe devices

Logan Gunthorpe
2016-12-05T19:27:20Z

On 05/12/16 12:14 PM, Jason Gunthorpe wrote:
> But CMB sounds much more like the GPU case where there is a
> specialized allocator handing out the BAR to consumers, so I'm not
> sure a general purpose chardev makes a lot of sense?

I don't think it will ever need to be as complicated as the GPU case.
There will probably only ever be a relatively small amount of memory
behind the CMB and really the only users are those doing P2P work. Thus
the specialized allocator could be pretty simple and I expect it would
be fine to just return -ENOMEM if there is not enough memory.

Also, if it was implemented this way, if there was a need to make the
allocator more complicated it could easily be added later as the
userspace interface is just mmap to obtain a buffer.

Logan