[openib-general] Re: Dual Sided RMPP Support as well as OpenSM Implications

[Roland Dreier]

    Hal> The simplest way I can think of to add this from an ABI/API
    Hal> perspective is to add an ioctl to user_mad for this. Prior to
    Hal> the kernel supporting this, libibumad can just return not
    Hal> supported for the "is dual sided" check for the current
    Hal> user_mad ABI version (which is 5). Anyone have any better
    Hal> ideas on how to accomplish this ?

Maybe it would be simpler to add a flag to the agent registration
request structure?  If you wanted to, you could even steal the high
order bit of the QPN field and do this in a backwards compatible way.

    Hal> Also, there is the question of what should the existing RMPP
    Hal> code do if it receives dual sided RMPP request on the network
    Hal> side. It could ABORT this request although RMPP currently has
    Hal> no specific status code for this. This is likely an issue
    Hal> with any other dual sided RMPP implementations and there
    Hal> would be no guarantee of interoperability here. It's unclear
    Hal> what RMPP implementations which do not support dual sided
    Hal> would do: likely just handle it as if it weren't dual sided.

I don't see how we can change the behavior of the existing code
without a time machine -- it does whatever it does...

 - R.