linux-kernel - Re: [PATCH 3/4] perf, x86: check ucode before disabling PEBS on SandyBridge v3

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Date:	Wed, 13 Jun 2012 23:30:54 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org, eranian@...gle.com,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 3/4] perf, x86: check ucode before disabling PEBS on
 SandyBridge v3

On Wed, 2012-06-13 at 13:20 -0700, Andi Kleen wrote:

> +static int check_pebs_quirks(void)
> +{
> +	int model = cpu_data(smp_processor_id()).x86_model;
> +
> +	/* do not have PEBS to begin with */
> +	if (!x86_pmu.pebs)
> +		return 0;
> +
> +	/*
> +	 * check ucode version for SNB, SNB-EP
> +	 */
> +	if ((model == 42 && boot_cpu_data.microcode < 0x28) ||
> +		(model == 45 && boot_cpu_data.microcode < 0x618)) {

Stephane actually wrote:

"Ok, so to close on this, I tried the 6/6/2012 ucode update on a few
SNB-EP systems.

I got two answers depending on the stepping:
C1 (stepping 6) -> 0x618
C2 (stepping 7) -> 0x70c

So we need to check x86_mask for stepping and adjust the value of
snb_ucode_rev accordingly for model 45."

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