Hello,

Andre Wild reported that fake NUMA doesn't work on s390 anymore. Doesn't
work means it crashed for Andre, or it is in an endless loop within
init_sched_groups_capacity() for me (sg != sd->groups is always true).

I could reproduce this with a very simple setup with only two nodes, where
each node has only one CPU. This allowed me to bisect it down to commit
051f3ca02e46 ("sched/topology: Introduce NUMA identity node sched domain").

With that commit reverted the system comes up again and the scheduling
domains look like this:

[    0.148592] smp: Bringing up secondary CPUs ...
[    0.148984] smp: Brought up 2 nodes, 2 CPUs
[    0.149097] CPU0 attaching sched-domain(s):
[    0.149099]  domain-0: span=0-1 level=NUMA
[    0.149101]   groups: 0:{ span=0 }, 1:{ span=1 }
[    0.149106] CPU1 attaching sched-domain(s):
[    0.149107]  domain-0: span=0-1 level=NUMA
[    0.149108]   groups: 1:{ span=1 }, 0:{ span=0 }
[    0.149111] span: 0-1 (max cpu_capacity = 1024)

Any idea what's going wrong?

Config file is attached.

Thanks,
Heiko