linux-kernel - Re: [PATCH RESEND v7 02/21] drivers/perf: apple_m1: Only init PMUv3 remap when EL2 is available

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Message-ID: <81addd64-6ba6-465e-901e-05f9cb29185b@gmail.com>
Date: Mon, 14 Jul 2025 23:37:46 +0800
From: Nick Chan <towinchenmi@...il.com>
To: Will Deacon <will@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Catalin Marinas <catalin.marinas@....com>,
 Janne Grunau <j@...nau.net>, Alyssa Rosenzweig <alyssa@...enzweig.io>,
 Neal Gompa <neal@...pa.dev>, Sven Peter <sven@...nel.org>,
 Marc Zyngier <maz@...nel.org>, linux-arm-kernel@...ts.infradead.org,
 linux-perf-users@...r.kernel.org, devicetree@...r.kernel.org,
 asahi@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND v7 02/21] drivers/perf: apple_m1: Only init PMUv3
 remap when EL2 is available


Will Deacon 於 2025/7/14 夜晚11:11 寫道:
> On Mon, Jun 16, 2025 at 09:31:51AM +0800, Nick Chan wrote:
>> Skip initialization of PMUv3 remap when EL2 is not available.
>> Initialization is harmless in EL1 but it is still a weird thing to do.
> Why is that weird?

Maybe I could use better wording but if the check is not here, then for Apple A7 which has very
different event mappings, it either has to use the mappings for M1 which is wrong on the hardware,
or declare an a7_pmu_pmceid_map, which would just be dead code since A7's CPU does not
support EL2. Not initializing the mapping in EL1 avoid these problems.

>
> Will
>
Nick Chan