Quoting r. Sean Hefty <[EMAIL PROTECTED]>:
> Subject: Re: [PATCH] mad: add GID/class checking for matching received to
> sent MADs
>
> Jack Morgenstein wrote:
> >+static inline int rcv_has_same_gid(struct ib_mad_send_wr_private *wr,
> >+ struct ib_mad_recv_wc *rwc )
> >+{
> >+ struct ib_ah_attr attr;
> >+ u8 send_resp, rcv_resp;
> >+
> >+ send_resp = ((struct ib_mad *)(wr->send_buf.mad))->
> >+ mad_hdr.method & IB_MGMT_METHOD_RESP;
> >+ rcv_resp = rwc->recv_buf.mad->mad_hdr.method & IB_MGMT_METHOD_RESP;
> >+
> >+ if (!send_resp && rcv_resp)
> >+ /* is request/response. GID/LIDs are both local (same). */
> >+ return 1;
> >+
> >+ if (send_resp == rcv_resp)
> >+ /* both requests, or both responses. GIDs different */
> >+ return 0;
>
> The two checks above are only checking response bits of a sent and received
> MAD. How do these relate to checking the GIDs?
Well, the comments really explain what the checks do, don't they?
Would rcv_has_same_initiator be a better name?
> >+ if (ib_query_ah(wr->send_buf.ah, &attr))
> >+ /* Assume not equal, to avoid false positives. */
> >+ return 0;
>
> Querying for the address handle every time seems expensive.
Its a very cheap operation. Look at the implementation: the low level
driver already caches everything in hardware format, we just move
some bits around.
> Can't we save
> the necessary information inside the ah?
That would waste a lot of memory.
Its not worth caching it. Our locking rules require for query_ah to be atomic
which is a strong hint that it just retrieves the data cached by low level
driver.
> Failing that, we should move the
> query when sending a MAD, so it can be done once.
We do it on receive to match ACKs to transactions.
I dont see how this check can be done on send.
Patch?
--
Michael S. Tsirkin
Staff Engineer, Mellanox Technologies
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