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

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Message-ID: <20180619200115.GH2494@hirez.programming.kicks-ass.net>
Date:   Tue, 19 Jun 2018 22:01:15 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
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, 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.