[REGRESSION] v6.8 SMC-D issues

Alexandra Winter
2024-01-24T14:29:51Z

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>