linux-kernel - smpboot seems to be confused on dual EPYC system

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Date:   Sun, 20 May 2018 15:23:32 +0200
From:   Gabriel C <nix.or.die@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     X86 ML <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>
Subject: smpboot seems to be confused on dual EPYC system

Hello,

I have an H11DSi-NT board with 2 *  EPYC 7281 16C/32T CPUs.

On that box for some reason spmboot things '4' logical packages
are possible.

Max CPUs can be 128 ( 2 * 32C/64T ), however only 2 CPUs are possible
not 4 and therefor there is no way to add other 64 hotplug CPUs.
( not even sure cpu hotplug will work here )

$ dmesg | egrep "smpboot|NR_CPUS|CPUs"
[    0.000000] smpboot: Allowing 128 CPUs, 64 hotplug CPUs
[    0.000000] setup_percpu: NR_CPUS:8192 nr_cpumask_bits:128
nr_cpu_ids:128 nr_node_ids:8
[    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=128, Nodes=8
[    0.000000]  RCU restricting CPUs from NR_CPUS=8192 to nr_cpu_ids=128.
[    0.037000] smpboot: CPU0: AMD EPYC 7281 16-Core Processor (family:
0x17, model: 0x1, stepping: 0x2)
[    0.048005] smp: Bringing up secondary CPUs ...
[    0.055042] .... node  #0, CPUs:          #1   #2   #3
[    0.079029] .... node  #1, CPUs:     #4   #5   #6   #7
[    0.111049] .... node  #2, CPUs:     #8   #9  #10  #11
[    0.143050] .... node  #3, CPUs:    #12  #13  #14  #15
[    0.175031] .... node  #4, CPUs:    #16  #17  #18  #19
[    0.217031] .... node  #5, CPUs:    #20  #21  #22  #23
[    0.249062] .... node  #6, CPUs:    #24  #25  #26  #27
[    0.281058] .... node  #7, CPUs:    #28  #29  #30  #31
[    0.313028] .... node  #0, CPUs:    #32  #33  #34  #35
[    0.345028] .... node  #1, CPUs:    #36  #37  #38  #39
[    0.377046] .... node  #2, CPUs:    #40  #41  #42  #43
[    0.409043] .... node  #3, CPUs:    #44  #45  #46  #47
[    0.441028] .... node  #4, CPUs:    #48  #49  #50  #51
[    0.473029] .... node  #5, CPUs:    #52  #53  #54  #55
[    0.505060] .... node  #6, CPUs:    #56  #57  #58  #59
[    0.537052] .... node  #7, CPUs:    #60  #61  #62  #63
[    0.562171] smp: Brought up 8 nodes, 64 CPUs
[    0.562171] smpboot: Max logical packages: 4
[    0.562171] smpboot: Total of 64 processors activated (268089.53 BogoMIPS)

Can someone have a look ?

Best Regards,

Gabriel C