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Subject: Re: [RFC PATCH -v2.1] x86: Kill notsc
To: Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@alien8.de>
References: <20151018142007.GA11294@pd.tnic> <20151021175803.GF3575@pd.tnic>
 <20151021190109.GC2508@worktop.programming.kicks-ass.net>
 <20151022185122.GC3442@pd.tnic> <alpine.DEB.2.11.1511041120120.4032@nanos>
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 <alpine.DEB.2.11.1511162158570.3761@nanos>
Cc: Peter Zijlstra <peterz@infradead.org>, x86-ml <x86@kernel.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Steven Rostedt <rostedt@goodmis.org>,
        lkml <linux-kernel@vger.kernel.org>
From: "H. Peter Anvin" <hpa@zytor.com>
Message-ID: <564AB4D7.20606@zytor.com>
Date: Mon, 16 Nov 2015 21:02:15 -0800
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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.

	-hpa