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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aHkT0BIyuUVvI4Ht@willie-the-truck>
Date: Thu, 17 Jul 2025 16:16:32 +0100
From: Will Deacon <will@...nel.org>
To: Nick Chan <towinchenmi@...il.com>
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

On Mon, Jul 14, 2025 at 11:37:46PM +0800, Nick Chan wrote:
> 
> 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.

That's definitely more motivating than what you have :)

Will