[openib-general] [PATCH] librdmacm: fix bug causing failure to work with partial membership pkey

[Hal Rosenstock]

On Thu, 2007-02-22 at 17:18, Sean Hefty wrote:
> >>Can someone help my understanding here?  Is ipoib joining a multicast group
> >>using the full membership PKey, even if the node that it joins from only has the
> >>limited membership PKey configured? And the code in ib_find_cached_pkey helps
> >>enable this?
> > 
> > Yep. The ipoib create_child  function Or-s 0x8000  to the device pkey
> > which was provided by the user. Now, IPoIB uses the device pkey when
> > forming MGIDs and when doing modify qp to init. Indeed the way
> > ib_find_cached_pkey() is implemented, make the latter use trivial.
> 
> Doesn't this allow ipoib to join a multicast group for which it may not be able 
> to communicate with all members?

Yes, if the join were to succeed which appears to be to be noncompliant
behavior.

> For the broadcast group, this seems like an error to me.

Why for just the broadcast group ? Isn't it any IPoIB MC group for which
this would be done ? (See below as to what the IBA spec says).

> Can ipoib work in such a configuration?  If all nodes were 
> assigned a partial membership PKey, none of them could communicate, but no 
> errors would be generated anywhere.
> 
> Joining a multicast group requires specifying the full membership PKey.  I don't 
> see anything in the spec that explicitly prohibits joining the group from a node 
> with only a partial membership PKey,

What about the description og P_Key in MCMemberRecord (table 210 on p.
908 which is compliance) which states:

"All members of the multicast group shall have full membership in the
partition indicated by the partition key."

-- Hal

>  but at first glance, this seems like a 
> subnet configuration issue.  Is there some use of this I'm overlooking?
> 
> - Sean