[openib-general] Re: uverbs: When message is larger than receive buffer

[Michael S. Tsirkin]

Quoting r. Steve Wooding <steve_wooding at keysounds.co.uk>:
> Subject: Re: uverbs: When message is larger than receive buffer
> 
> Thanks Micheal.
> 
> Can I confirm that no memory beyond that specified in the WR for the
> Send op is not actually written to.

Yes, IB spec guarantees that.

> The reason I'm interested in this is that I'm thinking about registering a
> large Memory Region to receive lots of smaller data messages. This is to avoid
> the overhead of registering and unregistering MRs. For RDMA Write, would
> windowing be the only option to stop a sender writing beyond what the receiver
> was expecting?
> 
> Regards,
> 
> Steve.

Not sure what you mean. No memory beyond that specified in the WR for
the Send op is written to.

So you can either: use memory windows (not yet supported in mthca AFAIK),
set the region to match the buffer that you want to write to exactly,
or trust the sender not to post send wr outside this buffer.
Our SDP implementation takes the last approach.

-- 
MST