New mca parameter is added (ib_path_rec_service_level) - positive value means that we should get the SL from the SA.
This is usable for torus topologies where different SL value is used for different endpoints.
A cache is kept of ib queue pairs used to communicate with the SA for a particular device and port and path record SL values retrieved from that SA.
The interaction with the cache assumes that there are no recursive calls to these routines. This must be solved either by code flow, by using higher level locks, or by adding a locking mechanism to these routines along with some method for avoiding deadlock.
This code use a UD queue pair to talk to the SA, and not need to chmod /dev/infiniband/umad* for use by normal users.
The request to the SA is a SubnAdmGet(), not a SubnAdmGetTable().
In the future we might add a support of a SubnAdmGetTable(), but it will require implementing RMPP (Reliable Multi-Packet Transaction Protocol) and I'm not sure we want to do that.
This patched is based on the work of David McMillen <davem@systemfabricworks.com>.
This commit was SVN r24195.
834625cc51