[openib-general] APM: SM port failover

[Venkatesh Babu]

 Let us say there are two nodes A and B. NodeA (passive side) passively 
listens for RC QP connection establishment requests and NodeB (active 
side) initiates the RC QP connection request with ib_send_cm_req(). When 
a port failure occurs on NodeA (passive side), it gets the event 
IB_EVENT_PORT_ERR locally. So it can call ib_modify_qp() for the RC QP 
to change the path_mig_state to IB_MIG_MIGRATED to use the alternate 
path. No problem here. But NodeB has to register with the OpenSM for the 
port failure event on NodeA, so that it can call ib_modify_qp() on the 
active side.

This is working fine by using the interface ib_sa_serv_notice_hdlr() 
described in bug#159 
(https://staging.openfabrics.org/bugzilla/show_bug.cgi?id=159).

  Now the question is - what if NodeA is running OpenSM with port 1 
(sm_port=1), and that port fails (say cable disconnect). Then Node B can 
not receive any notification of the port failure even though it has 
registered for the notice handler with ib_sa_serv_notice_hdlr(), because 
sm_port is down.

  How can we handle the port failover in this scenario ?

 VBabu