[openib-general] sharing qp between user and kernel

[Roland Dreier]

    Pete> Before I dig into this anymore, do you expect this to work?
    Pete> Are there fundamental problems with QP sharing between user
    Pete> and kernel?  It would sure be nice not to have to stick the
    Pete> connection management aspects into the kernel.

No, I wouldn't expect this to work.  At first glance at least, yes,
there are fundamental problems.  Sharing a QP between user and
kernelspace, where userspace is doing full kernel bypass (as eg mthca
does -- there are NO system calls when doing post work request, poll
CQ and request CQ notification operations), seems like a huge
problem.  I don't see any way that the kernel can keep a consistent
view of the QP state unless userspace has to call into the kernel for
every operation, which would kill performance.

 - R.