linux-kernel - Re: [PATCH v10 1/7] x86/tsc: remove tsc

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Message-ID: <alpine.DEB.2.21.1806192256370.10546@nanos.tec.linutronix.de>
Date:   Tue, 19 Jun 2018 22:57:35 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Pavel Tatashin <pasha.tatashin@...cle.com>,
        steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        linux@...linux.org.uk, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, john.stultz@...aro.org,
        sboyd@...eaurora.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, hpa@...or.com, douly.fnst@...fujitsu.com,
        prarit@...hat.com, feng.tang@...el.com, pmladek@...e.com,
        gnomes@...rguk.ukuu.org.uk
Subject: Re: [PATCH v10 1/7] x86/tsc: remove tsc_disabled flag

On Tue, 19 Jun 2018, Peter Zijlstra wrote:

> On Tue, Jun 19, 2018 at 09:12:45PM +0200, Thomas Gleixner wrote:
> > On Tue, 19 Jun 2018, Peter Zijlstra wrote:
> > > It does not; there is TSC usage even if you boot with notsc on. See how
> > > it does not clear X86_FEATURE_TSC for instance.
> > 
> > Well, kinda. There is some stuff in the apic calibration which uses TSC
> > independent of tsc_disabled, but that's about it.
> 
> Still, that precludes booting on hardware without TSC, so what's the
> point of having notsc? I'm all for killing the thing.

I'm not arguing against removing it. I just refuse to accept changelogs
which suggest that there is no functional change.

Thanks,

	tglx