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SubjectRe: Kernel 6.9 regression: X86: Bogus messages from topology detection
Date
On Mon, May 27 2024 at 09:29, Peter Schneider wrote:
> This is coming from an older server machine: 2-socket Ivy Bridge Xeon E5-2697 v2 (24C/48T)
> in an Asus Z9PE-D16/2L motherboard (Intel C-602A chipset); BIOS patched to the latest
> available from Asus. All memory slots occupied, so 256 GB RAM in total.
>
> From a "good boot", e.g. kernel 6.8.11, dmesg output looks like this:
>
> [ 1.823797] smpboot: x86: Booting SMP configuration:
> [ 1.823799] .... node #0, CPUs: #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11
> [ 1.827514] .... node #1, CPUs: #12 #13 #14 #15 #16 #17 #18 #19 #20 #21 #22 #23
> [ 0.011462] smpboot: CPU 12 Converting physical 0 to logical die 1
>
> [ 1.875532] .... node #0, CPUs: #24 #25 #26 #27 #28 #29 #30 #31 #32 #33 #34 #35
> [ 1.882453] .... node #1, CPUs: #36 #37 #38 #39 #40 #41 #42 #43 #44 #45 #46 #47
> [ 1.887532] MDS CPU bug present and SMT on, data leak possible. See
> https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.
> [ 1.933640] smp: Brought up 2 nodes, 48 CPUs
> [ 1.933640] smpboot: Max logical packages: 2
> [ 1.933640] smpboot: Total of 48 processors activated (259199.61 BogoMIPS)
>
>
> From a "bad" boot, e.g. kernel 6.9.2, dmesg output has these messages in it:
>
> [ 1.785937] smpboot: x86: Booting SMP configuration:
> [ 1.785939] .... node #0, CPUs: #4
> [ 1.786215] .... node #1, CPUs: #12 #16

Yuck. That does not make any sense.

> [ 1.797547] .... node #0, CPUs: #1 #2 #3 #5 #6 #7 #8 #9 #10 #11
> [ 1.801858] .... node #1, CPUs: #13 #14 #15 #17 #18 #19 #20 #21 #22 #23
> [ 1.804687] .... node #0, CPUs: #24 #25 #26 #27 #28 #29 #30 #31 #32 #33 #34 #35
> [ 1.810728] .... node #1, CPUs: #36 #37 #38 #39 #40 #41 #42 #43 #44 #45 #46 #47

> However the machine boots, and except from these strange messages, I cannot detect any
> other abnormal behaviour. It is running ~15 QEMU/KVM virtual machines just fine. Because
> these messages look unusual and a bit scary though, I have bisected the issue, to be able
> to report it here. The first bad commit I found is this one:

Ok. So as the machine is booting, can you please provide the output of:

cat /sys/kernel/debug/x86/topo/cpus/*

on the 6.9 kernel and

cat /proc/cpuinfo

for both 6.8 and 6.9?

Thanks,

tglx

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