[openib-general] What could prevent a gen2 x86 client qp from doing RDMA_READ on a gen1 PowerPC client?

[dotanb at dev.mellanox.co.il]

> Endian-ness issues?
> Yes that is the first thought.
>
> But where?
> Since my gen2 x86 rdma code can do an rdma read from  a gen1 and gen2
> x86 server I think the only values in the ibv_send_wr that can be wrong
> talking to a PowerPC server can be remote_addr and rkey right
> I already swapped both but without success.
>
> Are there other places in the ibv_send_wr or the underlying code that
> might be endian-ness fooled?
> Since I can do a VAPI_SEND (non RDMA) from the gen2 x86 client to the
> gen1 PowerPC server I think the qp should be OK?
>
> Is there something RDMA READ specific in the qp that still might not be
> right after my CM connection from gen2 to gen1?
> Don't forget the RDMA WRITE from the gen1 PowerPC server to the gen2 x86
> client on the same qp works just before the RDMA READ from gen2 x86
> client on the gen1 PowerPC server fails.
>
> Still confusing.
> Thomas
>

Yes. there are 2 attributes in every QP that handles RDMA Reads/Atomic
operations:
a) how many outstanding RDMA Read atomic the QP may send as an initiator
b) how many outstanding RDMA Read atomic the QP may send as a target

the connectivty between QPs X and Y should be:
Xa = Yb
Xb = Ya

and ofcourese RDMA Read need to be enabled in the QP access permissions
and in the MR permissions ...

Dotan