linux-kernel - Re: [PATCH] x86/tsc: Have tsc=recalibrate override things

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Message-ID: <20231030160344.GA19106@noisy.programming.kicks-ass.net>
Date:   Mon, 30 Oct 2023 17:03:44 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Arjan van de Ven <arjan@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        feng.tang@...el.com
Subject: Re: [PATCH] x86/tsc: Have tsc=recalibrate override things

On Mon, Oct 30, 2023 at 05:00:50PM +0100, Peter Zijlstra wrote:
> Hi,
> 
> My brand-spanking new SPR supermicro workstation was reporting NTP
> failures:
> 
> Oct 30 13:00:26 spr ntpd[3517]: CLOCK: kernel reports TIME_ERROR: 0x41: Clock Unsynchronized
> Oct 30 13:00:58 spr ntpd[3517]: CLOCK: time stepped by 32.316775
> Oct 30 13:00:58 spr ntpd[3517]: CLOCK: frequency error 41699 PPM exceeds tolerance 500 PPM
> 
> CPUID provides:
> 
>     Time Stamp Counter/Core Crystal Clock Information (0x15):
>        TSC/clock ratio = 200/2
>        nominal core crystal clock = 25000000 Hz
>     Processor Frequency Information (0x16):
>        Core Base Frequency (MHz) = 0x9c4 (2500)
>        Core Maximum Frequency (MHz) = 0x12c0 (4800)
>        Bus (Reference) Frequency (MHz) = 0x64 (100)
> 
> and the kernel believes this. Since commit a7ec817d5542 ("x86/tsc: Add
> option to force frequency recalibration with HW timer") there is the
> tsc=recalibrate option, which forces the recalibrate.
> 
> This duely reports:
> 
> Oct 30 12:42:39 spr kernel: tsc: Warning: TSC freq calibrated by CPUID/MSR differs from what is calibrated by HW timer, please check with vendor!!
> Oct 30 12:42:39 spr kernel: tsc: Previous calibrated TSC freq:         2500.000 MHz
> Oct 30 12:42:39 spr kernel: tsc: TSC freq recalibrated by [HPET]:         2399.967 MHz

Arjan, can you please escalate this to our supermicro contact?