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

[Or Gerlitz]

Sean Hefty wrote:
>> 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?

My understanding is that when an IPoIB broadcast domain contains both 
partial and full members (*) attempts to communicate between two partial 
members would silently fail, does this silence is something you think we 
should work to change?

(*) eg when you have bunch or clients and a server or bunch of servers 
and you don't want to allow --clients-- to communicate among themselves)

> 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.

My thinking is that if in the end of this thread we are willing to move 
forward without changing ib_find_cached_pkey() then this patch should be 
merged.

Or.