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Date: Mon, 1 Sep 2014 15:41:12 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, eranian@google.com,
        Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH 4/5] perf, x86: Add INST_RETIRED.ALL workarounds
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On Mon, Aug 25, 2014 at 03:43:30PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
> 
> On Broadwell INST_RETIRED.ALL cannot be used with any period
> that doesn't have the lowest 6 bits cleared. And the period
> should not be smaller than 128.
> 
> Add a new callback to enforce this, and set it for Broadwell.
> 
> This is erratum BDM57 and BDM11.

This changelog could do with more words on the solution, esp. such that
you answer Stephanes question.