[openib-general] Reserved L_Key API

[Roland Dreier]

    Fabian> I think you still need reg_phys_mr (or some way to get an
    Fabian> RKEY) for kernel clients that do RDMA (SRP or kernel SDP,
    Fabian> for example).  Something like an RKEY with translation off
    Fabian> but PD enforcement (I don't think you want to get rid of
    Fabian> PD enforcement for that kind of usage).  Given this, I
    Fabian> would suggest keeping similar semantics as memory
    Fabian> registration.

First, just to be clear, I'm not suggesting that we get rid of
reg_phys_mr (although it would make sense for a low-level driver for
a stupid TCA not to support the operation).

I don't think consumers ever really want to pass remote entities an
R_Key with translation off (which would allow RDMA to arbitrary
addreses).  I think the solution for creating R_Keys is FMRs (either
Tavor-style or verbs extension-style).

 - R.