[ofa-general] Re: [PATCH] core/cm: improverequestmessage interpretation of subnet local fields

[Jim Hall]

Is it valid to have a CM request message with subnet local = 1 and hop limit 
 > 1?
If so, then it's not clear in the spec on how each side of the QP creation 
are to determine if they use GRHs or not.
Can Mellanox be configured to accept both (LRH,LRH_GRH) on a RC QP at the 
same time?

- Jim

----- Original Message ----- 
From: "Sean Hefty" <sean.hefty at intel.com>
To: "'Jason Gunthorpe'" <jgunthorpe at obsidianresearch.com>; "Sean Hefty" 
<mshefty at ichips.intel.com>
Cc: <general at lists.openfabrics.org>
Sent: Monday, September 17, 2007 1:39 PM
Subject: RE: [ofa-general] Re: [PATCH] core/cm: improverequestmessage 
interpretation of subnet local fields


> >I'm with Hal on this - why does this cause a problem? There is no IB
>>packet verification check that tests if a GRH is present, only if it
>>is presen it must be valid - so how can an extra correctly filled in
>>GRH cause anything but degraded performance?
>
> ib_init_ah_from_path() uses the hop_limit in the path record to determine 
> if a
> GRH should be used.  It sets the address handle attributes (used to 
> configure
> the QP) based on hop_limit > 1.  If hop_limit is set incorrectly in the CM 
> REQ,
> the path record formed by the CM based on data carried in the REQ could 
> have
> invalid GRH values.
>
> It's possible that this is an active side CM issue, but that's not clear 
> to me.
>
> - Sean
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