linux-kernel - Re: [RFC PATCH -v2.1] x86: Kill notsc

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Message-ID: <20151117085345.GB8819@pd.tnic>
Date:	Tue, 17 Nov 2015 09:53:46 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>, x86-ml <x86@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH -v2.1] x86: Kill notsc

On Mon, Nov 16, 2015 at 09:02:15PM -0800, H. Peter Anvin wrote:
> On 11/16/15 13:25, Thomas Gleixner wrote:
> > On Mon, 16 Nov 2015, Borislav Petkov wrote:
> >> -/*
> >> - * disable flag for tsc. Takes effect by clearing the TSC cpu flag
> >> - * in cpu/common.c
> >> - */
> >> -int __init notsc_setup(char *str)
> >> +/* Disable the TSC feature flag to avoid further TSC use. */
> >> +int __init notsc_setup(void)
> >>  {
> >> +#ifndef CONFIG_X86_TSC
> >>  	setup_clear_cpu_cap(X86_FEATURE_TSC);
> > 
> > This is silly, really.
> > 
> > If CONFIG_X86_TSC is disabled then we should just not compile tsc.c at
> > all and map cpu_has_tsc and stuff depending on it to false.
> > 
> 
> CONFIG_X86_TSC means TSC is obligatory, not that it is supported.

Hmm, I'd still need to untangle tsc.c though for people who want to
disable it for whatever reason.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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