linux-kernel - Re: [PATCH 9/9] x86, perf: Move PMU ACK after LBR read

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Message-ID: <20150511162354.GA21418@twins.programming.kicks-ass.net>
Date:	Mon, 11 May 2015 18:23:54 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	eranian@...gle.com, linux-kernel@...r.kernel.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 9/9] x86, perf: Move PMU ACK after LBR read

On Sun, May 10, 2015 at 12:22:47PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> With Arch Perfmon v4 the PMU ack unfreezes the LBRs. So we need to do
> the PMU ack after the LBR reading, otherwise the LBRs would be polluted by the
> PMI handler.

Hmm, we should move these last three patches before the SKL enablement
patch no, otherwise things will misbehave -- say a bisection lands in
between.

/me shuffles patches.

> This is a minimal change. In principle the ACK could be moved much later.

Right, so the more complete change would be to use the new and improved
FREEZE_ON_PMI and reenable both the LBRs and the CTRs with the
STATUS_RESET MSR, right?

Does it make sense to have a new handle_irq() routine for that?
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