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Message-ID: <951176ce-5fcc-4e5a-a25f-df0f7724e797@linux.ibm.com>
Date: Wed, 24 Jan 2024 15:44:57 +0100
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Subject: Re: [REGRESSION] v6.8 SMC-D issues
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From: Alexandra Winter <wintera@linux.ibm.com>
To: Wen Gu <guwen@linux.alibaba.com>, wenjia@linux.ibm.com, hca@linux.ibm.com,
        gor@linux.ibm.com, agordeev@linux.ibm.com, davem@davemloft.net,
        edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
        jaka@linux.ibm.com, Matthew Rosato <mjrosato@linux.ibm.com>
Cc: Linux regressions mailing list <regressions@lists.linux.dev>,
        borntraeger@linux.ibm.com, svens@linux.ibm.com,
        alibuda@linux.alibaba.com, tonylu@linux.alibaba.com,
        raspl@linux.ibm.com, schnelle@linux.ibm.com,
        guangguan.wang@linux.alibaba.com, linux-s390@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Halil Pasic <pasic@linux.ibm.com>
References: <20231219142616.80697-1-guwen@linux.alibaba.com>
 <20231219142616.80697-8-guwen@linux.alibaba.com>
 <13579588-eb9d-4626-a063-c0b77ed80f11@linux.ibm.com>
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On 24.01.24 15:29, Alexandra Winter wrote:
> Hello Wen Gu,
> 
> our colleague Matthew reported that SMC-D is failing in certain scenarios on
> kernel v6.8 (thx Matt!). He bisected it to 
> b40584d ("net/smc: compatible with 128-bits extended GID of virtual ISM device")
> I think the root cause could also be somewhere else in the SMC-Dv2.1 patchset.
> 
> I was able to reproduce the issue on a 6.8.0-rc1 kernel.
> I tested iperf over smc-d with:
> smc_run iperf3 -s
> smc_run iperf3 -c <IP@>
> 
> 1) Doing an iperf in a single system using 127.0.0.1 as IP@
> (System A=iperf client=iperf server)
> 2) Doing iperf to a remote system (System A=client; System B=iperf server)
> 
> The second iperf fails with an error message like:
> "iperf3: error - unable to receive cookie at server: Bad file descriptor" on the server"
> 
> If I do first 2) (iperf to remote) and then 1) (iperf to local), then the
> iperf to local fails.
> 
> I can do multiple iperf to the first server without problems.
> 
> I ran it on a debug server with KASAN, but got no reports in the Logfile.
> 
> I will try to debug further, but wanted to let you all know.
> 
> Kind regards
> Alexandra
> 
> Reported-by: Matthew Rosato <mjrosato@linux.ibm.com>
> 
> 
> 

It seems the issue only occurs, when both client and server are on 6.8+
When either side is on an older kernel (6.5.6-300.fc39.s390x in my case),
I don't see the issue.