linux-kernel - [REGRESSION] v6.8 SMC-D issues

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Message-ID: <13579588-eb9d-4626-a063-c0b77ed80f11@linux.ibm.com>
Date: Wed, 24 Jan 2024 15:29:26 +0100
From: Alexandra Winter <wintera@...ux.ibm.com>
To: Wen Gu <guwen@...ux.alibaba.com>, wenjia@...ux.ibm.com, hca@...ux.ibm.com,
        gor@...ux.ibm.com, agordeev@...ux.ibm.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        jaka@...ux.ibm.com, Matthew Rosato <mjrosato@...ux.ibm.com>
Cc: Linux regressions mailing list <regressions@...ts.linux.dev>,
        borntraeger@...ux.ibm.com, svens@...ux.ibm.com,
        alibuda@...ux.alibaba.com, tonylu@...ux.alibaba.com,
        raspl@...ux.ibm.com, schnelle@...ux.ibm.com,
        guangguan.wang@...ux.alibaba.com, linux-s390@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Halil Pasic <pasic@...ux.ibm.com>
Subject: [REGRESSION] v6.8 SMC-D issues

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@...ux.ibm.com>