[openib-general] cma private data length

[Hal Rosenstock]

On Fri, 2006-05-12 at 12:03, Steve Wise wrote:
> Sean/IB experts:
> 
> I'm running a version of rdma_bw from src/userspace/perftest that I
> ported to utilize the RDMA CMA library for connection setup (stay tuned
> for a patch to offer this to the trunk).  The CMA version exchanges the
> rkey information during RDMA connection setup using private data.  I
> noticed that over IB the private data length received is != to the size
> of the private data submitted by the application. I send 24 bytes both
> ways and always get 56 bytes in the RDMA_CM_EVENT_CONNECT_REQUEST event
> and 196 bytes on the RDMA_CM_EVENT_ESTABLISHED event.

That's what I'd expect as a full MAD lengthed packets are being
exchanged and the private data length is not encoded in the MAD. It
would need to be an explicit field in the consumer private data.

CM REQ private data is 736 bits which is 92 bytes, REP private data is
1568 bits (196 bytes). Some of the REQ private data is used for CMA and
the consumer private data is 56 bytes. See IP addressing annex.

> The first 24 bytes, however, are correct so the data is being exchanged.  Over iWARP,
> the lengths are 24...

> Is this a bug in the CMA or IB CM? 

Neither IMO.

-- Hal

> Thanks,
> 
> Steve.
> 
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