linux-kernel - Re: [PATCH v4 2/5] arm64: Allow a capability to be checked on a single CPU

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Message-ID: <20160422133209.GJ2998@e104818-lin.cambridge.arm.com>
Date:	Fri, 22 Apr 2016 14:32:09 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Suzuki K Poulose <suzuki.poulose@....com>
Cc:	linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
	marc.zyngier@....com, will.deacon@....com,
	linux-kernel@...r.kernel.org, Vadim.Lomovtsev@...iumnetworks.com
Subject: Re: [PATCH v4 2/5] arm64: Allow a capability to be checked on a
 single CPU

On Fri, Apr 22, 2016 at 12:25:32PM +0100, Suzuki K. Poulose wrote:
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1005,6 +1005,24 @@ static void __init setup_feature_capabilities(void)
>  	enable_cpu_capabilities(arm64_features);
>  }
>  
> +/*
> + * Check if the current CPU has a given feature capability.
> + * Should be called from non-preemptible context.
> + */
> +bool this_cpu_has_cap(unsigned int cap)
> +{
> +	const struct arm64_cpu_capabilities *caps = arm64_features;
> +
> +	if (WARN_ON(preemptible()))
> +		return false;
> +
> +	for (caps = arm64_features; caps->desc; caps++)
> +		if (caps->capability == cap && caps->matches)
> +			return caps->matches(caps, SCOPE_LOCAL_CPU);

Nitpick: you don't need to initialise "caps" twice.

Reviewed-by: Catalin Marinas <catalin.marinas@....com>