[ofa-general] [PATCH RFC] RDMA/cxgb3: Fixes for zero-stag.
swise at opengridcomputing.com
Mon Jun 30 09:57:37 PDT 2008
Roland Dreier wrote:
> > > How about enhancing the iWARP HW drivers implementation of
> > > get_dma_mr to switch on the access flags provided by the caller, and
> > > if no remote access it needed, just return zero stag for mr.lkey
> > > without doing any registration.
> > I think that sounds reasonable. I can add that for chelsio.
> that makes some sense although I don't know of any code that uses the
> zero STag or ib_get_dma_mr() with only local permissions to be honest,
> with the exception of IPoIB, which of course has no relevance to iwarp.
NFSRDMA was planning on using the zero stag for recvs on iwarp
transports. This boils down to only needing the zero stag + fastreg mrs
for NFSRDMA server over T3, avoiding dma_mrs which have limits in the T3 HW.
> Also using the zero STag breaks the semantics slightly in that there is
> no longer any PD attached to the key returned by ib_get_dma_mr().
True. I didn't think about this.
> Another point to note is that IB has the analogous concept of "reserved
> L_Key" which we could expose if anyone actually cared.
Hmm. A new API then? ib_get_local_lkey() or something? If IB mandates
the lkey be value of 0, then we need don't need to do anything...
More information about the general