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

[Hal Rosenstock]

On Wed, 2007-02-21 at 17:53, Hal Rosenstock wrote:
> On Wed, 2007-02-21 at 17:36, Sean Hefty wrote:
> > > It does this since its makes life simple and robust.
> > 
> > Is an SM prevented from loading two PKeys into an HCA's PKey table that differ 
> > by only the membership bit?
> 
> Nope.
> 
> > I can't think of any reason to do such a thing,
> 
> Me neither. It would be a configuration error of sorts.

It is vendor dependent whether the SM would allow this. As Sasha points
out, this cannot be done with OpenSM (at least currently).

-- Hal

> > but depending on which index was 
> > selected could limit which nodes you could communicate with.
> 
> > > Note that since the HCA validates the pkey in the in coming packet, no
> > > matter what the IB SW would do, partial members of a partition can't
> > > talk to each other. So the approach taken by the core/ipoib code was
> > > to just ignore the MSb in places where the code looks for the pkey
> > > --index-- and use the full member pkey when forming MGIDs. This seems
> > > fine to me.
> > 
> > My concern is that ib_find_cached_pkey() returns an index to a pkey that wasn't 
> > the one in the search.  Can this lead to a QP being configured in such a way 
> > that communication with a remote QP would silently fail?
> > 
> > I realize that a user could call ib_get_cached_pkey and see if the returned 
> > value matches the one in the original search, but this is a non-obvious way to 
> > check for a mismatch.
> > 
> > I'm not against this patch, but I want to make sure that I understand the 
> > issues, so we're not creating a work-around solution.  The patch is against the 
> > librdmacm, yet there's nothing that I see in the librdmacm that makes me think 
> > it's behaving incorrectly.
> 
> I'm not sure it's this patch in particular but it appears that there may
> be some non compliant behavior being exercised IMO.
> 
> -- Hal
> 
> > - Sean
> 
> 
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