[openib-general] [Fwd: RE: IB mcast question]

[Hal Rosenstock]

On Tue, 2006-08-15 at 17:13, Steve Wise wrote:
> On Tue, 2006-08-15 at 13:55 -0700, Roland Dreier wrote:
> 
> >  > App 1:
> >  > Creates QP with QKey=22
> >  > Joins multicast group 1 with QKey=33
> >  > 
> >  > App 2:
> >  > Creates QP with QKey=44
> >  > Joins multicast group 1
> >  > Sends to multicast group but with QKey=22
> > 
> > I think that last send is technically an IBA spec violation.
> > 
> >  - R.
> 
> You guys are confusing me.  "sends to multicast group but with
> QKey=22"... Does that mean you posted a SEND with the remote_qkey=22?
> 
> According to the spec, C10-15 sez the qkey in the outgoing packet will
> be the qkey from the QP context IF the high order bit of the qkey is
> set.  If the high order bit is _not_ set, then the outgoing packet will
> contain the qkey from the WR. (why? why?)

The high order bit is for controlled QKeys which are only supposed to be
sent by "privileged" consumers (e.g. MAD layer for QP1 handing).

Also, the C10-15 requirement does not speak to additional requirements
on the Q_Keys themselves like the one I cited to Sean in a previous
email in terms of multicast group addressing requirements.

> Now, in my experiment, my mcast qkey was 0xe00a0a0a

I don't think that should be allowed from user space.

-- Hal

>  and the qp qkeys
> were zero. So when the sender posted a SEND with remote_qkey=0xe00a0a0a,
> the interface placed the qkey from sender's qp, which was zero, in the
> packet.  That's why it worked I guess...
> 
> Now my head hurts...
> 
> 
> 
> 
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