linux-kernel - Re: [PATCH v7 1/4] arm64: cpufeature: Introduce MATCH_ALL_EARLY

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Message-ID: <4b74ff9d-7451-4c11-b9ad-66ffd83fd2d2@arm.com>
Date: Tue, 17 Jun 2025 11:20:32 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Mikołaj Lenczewski <miko.lenczewski@....com>,
 ryan.roberts@....com, yang@...amperecomputing.com, catalin.marinas@....com,
 will@...nel.org, jean-philippe@...aro.org, robin.murphy@....com,
 joro@...tes.org, maz@...nel.org, oliver.upton@...ux.dev, joey.gouly@....com,
 james.morse@....com, broonie@...nel.org, ardb@...nel.org, baohua@...nel.org,
 david@...hat.com, jgg@...pe.ca, nicolinc@...dia.com, jsnitsel@...hat.com,
 mshavit@...gle.com, kevin.tian@...el.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 iommu@...ts.linux.dev
Subject: Re: [PATCH v7 1/4] arm64: cpufeature: Introduce MATCH_ALL_EARLY_CPUS
 capability type

On 17/06/2025 10:51, Mikołaj Lenczewski wrote:
> From: Catalin Marinas <catalin.marinas@....com>
> 
> For system-wide capabilities, the kernel has the SCOPE_SYSTEM type. Such
> capabilities are checked once the SMP boot has completed using the
> sanitised ID registers. However, there is a need for a new capability
> type similar in scope to the system one but with checking performed
> locally on each CPU during boot (e.g. based on MIDR_EL1 which is not a
> sanitised register).
> 
> Introduce ARM64_CPUCAP_MATCH_ALL_EARLY_CPUS which, together with
> ARM64_CPUCAP_SCOPE_LOCAL_CPU, ensures that such capability is enabled
> only if all early CPUs have it. For ease of use, define
> ARM64_CPUCAP_EARLY_LOCAL_CPU_FEATURE which combines SCOPE_LOCAL_CPU,
> PERMITTED_FOR_LATE_CPUS and MATCH_ALL_EARLY_CPUS.
> 
> Signed-off-by: Catalin Marinas <catalin.marinas@....com>
> Signed-off-by: Mikołaj Lenczewski <miko.lenczewski@....com>
> Cc: Suzuki K Poulose <Suzuki.Poulose@....com>
> ---

Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>