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Date: Mon, 27 Feb 2017 18:40:46 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Paolo Bonzini <pbonzini@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>,
        Wanpeng Li <kernellwp@gmail.com>, Mike Galbraith <efault@gmx.de>,
        LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
        Borislav Petkov <bp@alien8.de>
Subject: Re: tip.today - scheduler bam boom crash (cpu hotplug)
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On Mon, 27 Feb 2017, Paolo Bonzini wrote:
> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index 2724dc82f992..3080b6877190 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -1398,6 +1398,9 @@ void __init tsc_init(void)
> 
>  	use_tsc_delay();
> 
> +	if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
> +		mark_tsc_unstable("not invariant");

Errm, no. 

That makes TSC unusable for systems which do not go into C/P states in
which the TSC stops. There is a world outside KVM ....

Thanks,

	tglx