[openib-general] Re: problem with SDP/AIO on mem-free HCA

[Fab Tillier]

> -----Original Message-----
> From: Roland Dreier [mailto:roland at topspin.com]
> Sent: Thursday, March 31, 2005 8:00 PM
> 
>     Michael> I dont think so.  I found this:
> 
>     Michael> C9-88: For an HCA responder using Reliable Connection
>     Michael> service, for each zero-length RDMA READ or WRITE request,
>     Michael> the R_Key shall not be validated, even if the request
>     Michael> includes Immediate data.
> 
>     Michael> Can it be you generate a non-zero RDMA in mthca.
> 
> It's possible.  I'll put some more work into testing this out soon.
> However it also seems possible that the current mem-free FW may have a
> bug in handling this.
> 
> SDP is generating the 0-length RDMA by posting an RDMA READ with a
> single scatter entry whole length is zero, which may behave
> differently from posting an RDMA READ with no scatter entries.  I need
> to check this out, and also test on Tavor.
> 

If you are blessed with a Tavor PRM, see section 8.2.1.6 (in PRM 1.0.0).  It
states that a length of zero in a data segment indicates a 2GB transfer (MSb
is used as a flag to indicate normal vs. inline data segments).  A zero-byte
request must not reference any data segments.

- Fab