[openib-general] RFC userspace CMA

[Sean Hefty]

Sean Hefty wrote:
> - The kernel CMA will expose a new call, rdma_init_qp_attr() to 
> initialize QP attributes used to modify the state of the QP.  The call 
> will be similar to the infiniband CM routine.  Use of this call is 
> optional.  The CMA will automatically transition QPs created by 
> rdma_create_qp().

The changes are more involved than this.  To handle the QP transitions in 
userspace, the kernel CMA needs to generate another event: CONNECT_RESPONSE.  It 
will also need an additional API: rdma_establish().  (We can overload 
rdma_accept() in place of rdma_establish().)  Basically, the 3-way handshake 
used by IB needs to be exposed.

Use of either of these can be limited to those users that do not associate a QP 
with their rdma_cm_id.  Alternatively, the uCMA kernel component can be 
integrated with the kernel CMA and make use of private interfaces.

- Sean