[ofa-general] OFED-1.3beta IPoIB testing questions

[Eli Cohen]

Hi Shirley,

I guess you missed my response to your comments too. They're attached.



On Mon, 2007-12-10 at 08:45 -0800, Shirley Ma wrote:
> Hello Eli,
> 
> I just found my email somehow became SPAM. I just resent my comments,
> hopefully it can go through.
> 
> Eli Cohen <eli at dev.mellanox.co.il> wrote on 12/02/2007 05:45:59 AM:
> 
> > On Fri, 2007-11-30 at 15:28 -0800, Shirley Ma wrote:
> > > I just touch tested ofed-1.3 beta IPoIB. And found there was a
> kernel 
> > > parameter hw_csum being added in IPoIB. I have several questions
> here:
> > > 1. Why not using ethtool to set up these HW_CSUM flags?
> > There is no adequate interface in Ethtool for doing it so we use a
> > module parameter. This is because we see this as a static
> configuration
> > per host.
> 
> Ethtool does support rx csum and tx csum:
> #define ETHTOOL_GRXCSUM  0x00000014 Get RX hw csum enable
> (ethtool_value)
> #define ETHTOOL_SRXCSUM  0x00000015 Set RX hw csum enable
> (ethtool_value)
> #define ETHTOOL_GTXCSUM  0x00000016 Get TX hw csum enable
> (ethtool_value)
> #define ETHTOOL_STXCSUM  0x00000017 /* Set TX hw csum enable
> (ethtool_value)
> 
> We should use ethtool here.
> 
> > > 2. I haven't looked at the detailed code yet, is that possible
> with this 
> > > flag, TCP/IP will not do CSUM for HCA which has no TCP/IP offload
> support? 
> > Yes, the HCA need not have checksum offload support. the idea is the
> IB
> > ICRC provides the insurance that the packets are not corrupt.
> 
> That's something we discussed long time ago when we wanted GSO to
> avoid extra copy by using ICRC to enable SG feature. I remembered
> Roland rejected this idea since there could be potenical data
> corruption. And even if we do prove that ICRC is 100% accurate, then
> we should have some codes here to limit the IP destination within IB
> subnet when using ICRC. Otherwise, if the packets routing out to
> ehthernet IP subnet, these packets will be dropped.
> 
> Thanks
> Shirley
> 
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From: Eli Cohen <eli at dev.mellanox.co.il>
Subject: Re: [ofa-general] OFED-1.3beta IPoIB testing questions
Date: Tue, 04 Dec 2007 18:15:25 +0200
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