linux-kernel - Re: PROBLEM: skew message does not handle negative ns skew

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Date:   Tue, 6 Jun 2023 20:42:48 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     Chris Bainbridge <chris.bainbridge@...il.com>
CC:     <paulmck@...nel.org>, <tglx@...utronix.de>, <sboyd@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: PROBLEM: skew message does not handle negative ns skew

On Tue, Jun 06, 2023 at 01:28:50PM +0100, Chris Bainbridge wrote:
> On Tue, 6 Jun 2023 at 12:35, Feng Tang <feng.tang@...el.com> wrote:
> >
> > Hi,
> >
> > Could you share more info about the hardware, like which generation,
> > how many sockets or numa nodes (output of lscpu, 'numactl -h') ?
> >
> > Thanks,
> > Feng
> 
> The hardware is a HP Pavilion Aero 13 laptop.
> 
> $ lscpu
> Architecture:            x86_64
>   CPU op-mode(s):        32-bit, 64-bit
>   Address sizes:         48 bits physical, 48 bits virtual
>   Byte Order:            Little Endian
> CPU(s):                  16
>   On-line CPU(s) list:   0-15
> Vendor ID:               AuthenticAMD
>   Model name:            AMD Ryzen 7 5800U with Radeon Graphics
>     CPU family:          25
>     Model:               80
>     Thread(s) per core:  2
>     Core(s) per socket:  8
>     Socket(s):           1
>     Stepping:            0
>     Frequency boost:     enabled
>     CPU(s) scaling MHz:  35%
>     CPU max MHz:         4505.0781
>     CPU min MHz:         1600.0000
>     BogoMIPS:            3792.93
>     Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep
> mtrr pge mca cmov
>                          pat pse36 clflush mmx fxsr sse sse2 ht
> syscall nx mmxext fxsr_
>                          opt pdpe1gb rdtscp lm constant_tsc rep_good
> nopl nonstop_tsc c
>                          puid extd_apicid aperfmperf rapl pni
> pclmulqdq monitor ssse3 f
>                          ma cx16 sse4_1 sse4_2 movbe popcnt aes xsave
> avx f16c rdrand l
>                          ahf_lm cmp_legacy svm extapic cr8_legacy abm
> sse4a misalignsse
>                           3dnowprefetch osvw ibs skinit wdt tce
> topoext perfctr_core pe
>                          rfctr_nb bpext perfctr_llc mwaitx cpb cat_l3
> cdp_l3 hw_pstate
>                          ssbd mba ibrs ibpb stibp vmmcall fsgsbase
> bmi1 avx2 smep bmi2
>                          erms invpcid cqm rdt_a rdseed adx smap
> clflushopt clwb sha_ni
>                          xsaveopt xsavec xgetbv1 xsaves cqm_llc
> cqm_occup_llc cqm_mbm_t
>                          otal cqm_mbm_local clzero irperf xsaveerptr
> rdpru wbnoinvd cpp
>                          c arat npt lbrv svm_lock nrip_save tsc_scale
> vmcb_clean flushb
>                          yasid decodeassists pausefilter pfthreshold
> avic v_vmsave_vmlo
>                          ad vgif v_spec_ctrl umip pku ospke vaes
> vpclmulqdq rdpid overf
>                          low_recov succor smca fsrm


There is a commit to lift the watchdog check for morden qualified
platforms: b50db7095fe0 ("Disable clocksource watchdog for TSC on
qualified platorms"). But the patforms need to have 'tsc_adjust'
feature (has a TSC_ADJUST MSR), which can't be found in the above
lscpu info.

And I'm have no idea if there is a real hardware/firmware issue
or just a false alarm.

Thanks,
Feng

> Virtualization features:
>   Virtualization:        AMD-V
> Caches (sum of all):
>   L1d:                   256 KiB (8 instances)
>   L1i:                   256 KiB (8 instances)
>   L2:                    4 MiB (8 instances)
>   L3:                    16 MiB (1 instance)
> NUMA:
>   NUMA node(s):          1
>   NUMA node0 CPU(s):     0-15
> Vulnerabilities:
>   Itlb multihit:         Not affected
>   L1tf:                  Not affected
>   Mds:                   Not affected
>   Meltdown:              Not affected
>   Mmio stale data:       Not affected
>   Retbleed:              Not affected
>   Spec store bypass:     Mitigation; Speculative Store Bypass disabled via prctl
>   Spectre v1:            Mitigation; usercopy/swapgs barriers and
> __user pointer saniti
>                          zation
>   Spectre v2:            Mitigation; Retpolines, IBPB conditional,
> IBRS_FW, STIBP alway
>                          s-on, RSB filling, PBRSB-eIBRS Not affected
>   Srbds:                 Not affected
>   Tsx async abort:       Not affected
> 
> $ numactl -H
> available: 1 nodes (0)
> node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
> node 0 size: 15331 MB
> node 0 free: 789 MB
> node distances:
> node   0
>   0:  10