linux-kernel - Re: [PATCH] arm64: Filter out SME hwcaps when FEAT

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Message-Id: <175164333073.1188085.16117765198083829346.b4-ty@kernel.org>
Date: Fri,  4 Jul 2025 18:44:10 +0100
From: Will Deacon <will@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>,
	Mark Brown <broonie@...nel.org>
Cc: kernel-team@...roid.com,
	Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Yury Khrustalev <yury.khrustalev@....com>,
	stable@...r.kernel.org
Subject: Re: [PATCH] arm64: Filter out SME hwcaps when FEAT_SME isn't implemented

On Fri, 20 Jun 2025 12:28:48 +0100, Mark Brown wrote:
> We have a number of hwcaps for various SME subfeatures enumerated via
> ID_AA64SMFR0_EL1. Currently we advertise these without cross checking
> against the main SME feature, advertised in ID_AA64PFR1_EL1.SME which
> means that if the two are out of sync userspace can see a confusing
> situation where SME subfeatures are advertised without the base SME
> hwcap. This can be readily triggered by using the arm64.nosme override
> which only masks out ID_AA64PFR1_EL1.SME, and there have also been
> reports of VMMs which do the same thing.
> 
> [...]

Applied to arm64 (for-next/fixes), thanks!

[1/1] arm64: Filter out SME hwcaps when FEAT_SME isn't implemented
      https://git.kernel.org/arm64/c/a75ad2fc76a2

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev