linux-kernel - Re: [RFC PATCH] tsc: synchronize TSCs on buggy Intel Xeon E5 CPUs with offset error

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Date:	Mon, 9 Nov 2015 23:02:32 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	gratian.crisan@...com
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Borislav Petkov <bp@...en8.de>, Josh Cartwright <joshc@...com>,
	gratian@...il.com
Subject: Re: [RFC PATCH] tsc: synchronize TSCs on buggy Intel Xeon E5 CPUs
 with offset error

On Mon, Nov 09, 2015 at 01:59:02PM -0600, gratian.crisan@...com wrote:

> The Intel Xeon E5 processor family suffers from errata[1] BT81:

> +#ifdef CONFIG_X86_TSC
> +	/*
> +	 * Xeon E5 BT81 errata: TSC is not affected by warm reset.
> +	 * The TSC registers for CPUs other than CPU0 are not cleared by a warm
> +	 * reset resulting in a constant offset error.
> +	 */
> +	if ((c->x86 == 6) && (c->x86_model == 0x3f))
> +		set_cpu_bug(c, X86_BUG_TSC_OFFSET);
> +#endif

That's hardly a family, that's just one, Haswell server.

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