Re: [PATCHv7 4/9] ib_core: RoCEE CMA device binding

[Eli Cohen <eli-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

On Thu, Jan 07, 2010 at 11:24:51AM -0700, Jason Gunthorpe wrote:
> On Thu, Jan 07, 2010 at 08:50:47AM -0800, Sean Hefty wrote:
> > >> > +	route->path_rec->hop_limit = 2;
> > >>
> > >
> > >The reason is that ib_init_ah_from_path() will not set IB_AH_GRH for
> > >hop_limit smaller then 2, and since that GRH is required in RoCEE, and
> > >since this is specific to RoCEE, I put 2 to make pass this.
> > 
> > A hop limit of 2 seems wrong though.  Isn't there some change that
> > could be made to ib_init_ah_from_path() that would work?  It seems
> > like the PR itself should indicate somehow whether the path is for
> > IB or Ethernet.  (Special LID values or some flag...)
> 

So, adding a flag to ib_init_ah_from_path() seems a reasonable
solution. This function is called from three places:
cm_init_av_by_path() and cma_sidr_rep_handler() can check the port
link layer and set a flag to request GRH for Ethernet link layers. The
other place is IPoIB:path_rec_completion() where we need not require
GRH since IPoIB over RoCEE is disable.


> I agree, on the wire the hop limit in the GRH should be 0 or 0xFF. 0
> is preferred since there is no support for routing.
> 

Why do you think we should use 0 for hop limit? Isn't 1 just as good?
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