[ewg] Re: [PATCH v3] libibmad: Handle MAD redirection

[Hal Rosenstock]

On Wed, Jul 1, 2009 at 11:17 AM, Joachim Fenkes<FENKES at de.ibm.com> wrote:
> Hal Rosenstock <hal.rosenstock at gmail.com> wrote on 01.07.2009 15:59:41:
>
>> > +static int redirect_port(ib_portid_t *port, uint8_t *mad)
>> > +{
>> > +       port->lid = mad_get_field(mad, 64, IB_CPI_REDIRECT_LID_F);
>> > +       if (!port->lid) {
>> > +               IBWARN("GID-based redirection is not supported");
>> > +               return -1;
>> > +       }
>>
>> Sorry for the confusion: determination of GID redirection should be
>> based on a comparison of the RedirectGID to 0. It's valid to supply
>> both a non zero RedirectGID and RedirectLID.
>
> Are you sure?

No; I'm not sure. See previous post to Jason.

> About the Redirection GID, the spec says "If redirection is not being
> performed, this shall be set to zero", so if redirection _is_ being
> performed, the GID may or may not be zero without any explicit
> implication.

Agreed but Jason doesn't appear to agree.

> For the LID, it says "If this value is zero, the redirect requires the
> requester to use the supplied RedirectGID to request further path
> resolution
> from subnet administration." To me, this explicitly states that a zero LID
> means that the GID must be used.
>
> If both LID and GID are non-zero, it is not specified whether the
> requester
> should use the LID or the GID, so I choose to always use the LID as long
> as it's non-zero, because that's what the code supports.

It does say that the LID might not be valid even though non-zero. I'm
thinking of the more general case (future) rather than just IBM eHCA
usage.

> Am I talking crazy or does this make sense to you?

>> > +
>> > +       port->qp = mad_get_field(mad, 64, IB_CPI_REDIRECT_QP_F);
>> > +       port->qkey = mad_get_field(mad, 64, IB_CPI_REDIRECT_QKEY_F);
>> > +       port->sl = mad_get_field(mad, 64, IB_CPI_REDIRECT_SL_F);
>> > +
>> > +       /* TODO: Reverse map redirection P_Key to P_Key index */
>> > +
>> > +       if (ibdebug)
>> > +               IBWARN("redirected to lid 0x%x, qp 0x%x, qkey 0x%x, sl
> 0x%x",
>> > +                      port->lid, port->qp, port->qkey, port->sl);
>>
>> Unicast LIDs should be displayed in decimal rather than hex.
>
> Couldn't you have noticed this in the first patch? ;)

Somehow I missed it :-( Sorry.

>I'll change it.

Thanks.

-- Hal

> Cheers,
>  Joachim
>