[openib-general] [RFC] Notice/InformInfo event reporting

[Sean Hefty]

I'm beginning work on adding InformInfo/Notice event reporting to the IB stack, 
and I'd like any input on potential implementations, as well as intended usage.

Clients use InformInfo to register for events, with registration tracked on a 
per source QP basis.  Given this, possible approaches are:

1. Clients can perform their own registration using their own QPs.  If several 
clients wish to register for the same event, multiple QPs would be used. 
Additional traffic would be used when reporting events.  But, event dispatching 
is centralized to the SA.

2. A single registration manager can perform all registrations.  This would 
require reference counting registration requests.  At a high level, the behavior 
is similar to what's done for multicast join/leave.  This limits use to a single 
QP, and minimizes traffic, but duplicates event dispatching code on every node.

2a.  Using option 2, a registration manager could register to receive all 
events, then filter based on local registration requests.  This would prevent 
overlapping requests to the SA, but increase the number of events seen at each 
end node.

2b.  Similar to option 2a, but clients would see all events (possibly filtered 
on type only), requiring that they perform additional filtering.

My current thinking is to register for all events, then require that clients 
filter unwanted events.  (Security events would be filtered from userspace clients.)

- Sean