linux-kernel - Re: [PATCH] perf/x86/rapl: Fix PP1 event for Intel Meteor/Lunar Lake

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Message-ID: <d25ef356-3614-4e69-8cc1-d74dbbd2585f@intel.com>
Date: Thu, 20 Feb 2025 08:28:01 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Lucas De Marchi <lucas.demarchi@...el.com>,
 linux-perf-users@...r.kernel.org, x86@...nel.org,
 linux-kernel@...r.kernel.org
Cc: dave.hansen@...ux.intel.com, Zhang Rui <rui.zhang@...el.com>,
 Kan Liang <kan.liang@...ux.intel.com>, Peter Zijlstra
 <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Ulisses Furquim <ulisses.furquim@...el.com>, intel-xe@...ts.freedesktop.org,
 intel-gfx@...ts.freedesktop.org
Subject: Re: [PATCH] perf/x86/rapl: Fix PP1 event for Intel Meteor/Lunar Lake

On 2/20/25 07:36, Lucas De Marchi wrote:
> On some boots the read of MSR_PP1_ENERGY_STATUS msr returns 0, causing
> perf_msr_probe() to make the power/events/energy-gpu event non-visible.
> When that happens, the msr always read 0 until the graphics module (i915
> for Meteor Lake, xe for Lunar Lake) is loaded. Then it starts returning
> something different and re-loading the rapl module "fixes" it.

What's the root cause here? Did the kernel do something funky? Or is
this a hardware bug?