linux-kernel - Re: [PATCH 1/1] x86 TSC: set X86_FEATURE_TSC

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Message-ID: <alpine.DEB.2.11.1506091014180.4133@nanos>
Date:	Tue, 9 Jun 2015 10:15:31 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andy Lutomirski <luto@...capital.net>
cc:	Len Brown <lenb@...nel.org>, Andy Lutomirski <luto@...nel.org>,
	X86 ML <x86@...nel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 1/1] x86 TSC: set X86_FEATURE_TSC_RELIABLE, per CPUID

On Mon, 8 Jun 2015, Andy Lutomirski wrote:
> On Wed, Jun 3, 2015 at 12:03 PM, Len Brown <lenb@...nel.org> wrote:
> > If you boot this machine with "tsc=reliable", to disable the cpu_up
> > check_tsc_sync,
> > what happens?  Does the run-time clocksource code detect the bogus TSC values?
> > If yes, how long does that take?
> 
> They didn't detect it in the time I watched it.

Which is not surprising as the run-time check is disabled with the
reliable flag as well.

        if (tsc_clocksource_reliable)
                clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;

Thanks,

	tglx
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