[openib-general] [PATCH] agent: Fix agent_mad_send PCI mapping and gather address and length

[Hal Rosenstock]

On Wed, 2004-11-10 at 16:29, Roland Dreier wrote:
>     Roland> I guess the problem with calling smi_handle_dr_smp_recv()
>     Roland> twice on the same packet is that the function may alter
>     Roland> the packet.
> 
>     Hal> No, the second call to smi_handle_dr_smp_recv() was on the
>     Hal> outgoing response and not the incoming request. The thought
>     Hal> was that a packet coming from process_mad is much like an
>     Hal> incoming received packet and hence the call to
>     Hal> smi_handle_dr_smp_recv. The routine validates the packet but
>     Hal> also can do some fixups depending on which case it falls
>     Hal> into. Guess it's only dangerous to validate this and wrong to
>     Hal> fix it up.
> 
> Maybe I'm misreading the code, but my patch deleted the call to
> smi_handle_dr_smp_recv() before the call to agent_send.  

You're not. I was...

> agent_send() eventually ends up in ib_post_send_mad(), which calls
> handle_outgoing_smp() for directed route MADs, which ends up calling
> smi_handle_dr_smp_recv() again.  Since smi_handle_dr_smp_recv() can
> change the packet, calling it twice on the same packet seems to break things.

I'm with you now.

> However I don't think it's a good idea to think of responses generated
> by process_mad as an incoming received packet.  I think they should be
> thought of as returning DR SMPs being passed to the SMI for sending
> (as in section 14.2.2 of the IB spec).

Yup, there is a difference between a returning SMP being sent and an
incoming SMP being received in terms of SMI. I was being imprecise
again.

>     Hal> The key to me is the following: The split of responsibility
>     Hal> on the DR header formation is a little unclear to me. In the
>     Hal> case of the SM, are the DR headers fully formed before
>     Hal> handing it to the MAD layer or is some DR fixup needed ?
> 
> My suggestion would be to follow the IB spec, and assume that the SM
> follows the SMP initialization in 14.2.2.1 and have the MAD layer just
> implement the SMI processing in 14.2.2.2.  (And I believe things
> should work similarly for responses generated by the SMA -- the MAD
> layer should just do SMI processing).

That was the intention. 

I will figure out what is broke but not just yet... I may want something
tried by either you or Sean prior to my checking it in to be sure. I'll
let you know.

Thanks.

-- Hal