linux-kernel - Re: [PATCH v1 09/13] perf/x86/amd: add idle hooks for branch sampling

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Message-ID: <YTnRyDT5iIlpk8Af@hirez.programming.kicks-ass.net>
Date:   Thu, 9 Sep 2021 11:20:08 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Stephane Eranian <eranian@...gle.com>
Cc:     linux-kernel@...r.kernel.org, acme@...hat.com, jolsa@...hat.com,
        kim.phillips@....com, namhyung@...nel.org, irogers@...gle.com
Subject: Re: [PATCH v1 09/13] perf/x86/amd: add idle hooks for branch sampling

On Thu, Sep 09, 2021 at 12:56:56AM -0700, Stephane Eranian wrote:
> On AMD Fam19h Zen3, the branch sampling (BRS) feature must be disabled before entering low power
> and re-enabled (if was active) when returning from low power. Otherwise, the NMI interrupt may
> be held up for too long and cause problems. Stopping BRS will cause the NMI to be delivered if it
> was held up.

What you sent me ^^^, vs reflow at 72 chars vvv:

On AMD Fam19h Zen3, the branch sampling (BRS) feature must be disabled
before entering low power and re-enabled (if was active) when returning
from low power. Otherwise, the NMI interrupt may be held up for too long
and cause problems. Stopping BRS will cause the NMI to be delivered if
it was held up.

(because git show has that stupid extra indentation for Changelogs)