linux-kernel - Re: [PATCH] clocksource: disable irq when holding watchdog

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Message-ID: <8734xy5r3i.ffs@tglx>
Date:   Wed, 25 Oct 2023 23:28:49 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        paulmck@...nel.org
Cc:     John Stultz <jstultz@...gle.com>, Stephen Boyd <sboyd@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        x86@...nel.org, joel@...lfernandes.org
Subject: Re: [PATCH] clocksource: disable irq when holding watchdog_lock.

On Tue, Oct 24 2023 at 23:52, Tetsuo Handa wrote:

> On 2023/10/24 22:00, Thomas Gleixner wrote:
>> Interesting. Can you please tell what the replacement clocksource is
>> when the TSC is disabled?
>
> Where can I find the replacement clocksource from?

/sys/kernel/devices/system/clocksource/clocksource0/active_clocksource

but I already figured it out. It selects kvm_clock as fallback, but that
happens way later. At that point during AP bringup timekeeping is still
based on jiffies. So that TSC unstable marking is not an issue
vs. timekeeping.

I have no idea what the kernel, VirtualPox or Windoze are doing during
that time. I fear you need to add some debug on your own or if
VirtualPox has a monitor/debugger you might use that to inspect what the
guest is doing.

Thanks,

        tglx