[ofa-general] Infiniband back-to-back without OpenSM?

[Talpey, Thomas]

Is it possible to manually configure two Infiniband ports to operate
with one another in back-to-back mode, without running OpenSM
on one of them?

We have done this on other IB implementations by manually assigning
LIDs, but I discover that the "lid" entry below /sys/class/infiniband/<device>
is not writable, at least for mthca. Also, I expect that the ipoib driver will
be unable to join the broadcast group, so will be unwilling to come up fully.

With ethernet, and maybe iWARP, just a simple ifconfig can do this. So why
not IB?

If you're wondering, my goal is give NFS/RDMA users a way to avoid having
to install the many userspace modules needed to do this, including libibverbs,
opensm, etc. There's a lot to get wrong, and things go missing. Seeking an
"easy" way to get started with just the kernel and some shell commands.

Tom.