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Date: Mon, 4 Dec 2023 18:46:40 +0000
From: Catalin Marinas <catalin.marinas@arm.com>
To: Joey Gouly <joey.gouly@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org,
	aneesh.kumar@linux.ibm.com, broonie@kernel.org,
	dave.hansen@linux.intel.com, maz@kernel.org, oliver.upton@linux.dev,
	shuah@kernel.org, will@kernel.org, kvmarm@lists.linux.dev,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-kselftest@vger.kernel.org, James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>
Subject: Re: [PATCH v3 03/25] arm64: cpufeature: add Permission Overlay
 Extension cpucap
Message-ID: <ZW4ekJ8pxwWTmVFC@arm.com>
References: <20231124163510.1835740-1-joey.gouly@arm.com>
 <20231124163510.1835740-4-joey.gouly@arm.com>
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In-Reply-To: <20231124163510.1835740-4-joey.gouly@arm.com>

On Fri, Nov 24, 2023 at 04:34:48PM +0000, Joey Gouly wrote:
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -2078,6 +2078,22 @@ config ARM64_EPAN
>  	  if the cpu does not implement the feature.
>  endmenu # "ARMv8.7 architectural features"
>  
> +menu "ARMv8.9 architectural features"
> +config ARM64_POE
> +	prompt "Permission Overlay Extension"
> +	def_bool y
> +	help
> +	  The Permission Overlay Extension is used to implement Memory
> +	  Protection Keys. Memory Protection Keys provides a mechanism for
> +	  enforcing page-based protections, but without requiring modification
> +	  of the page tables when an application changes protection domains.
> +
> +	  For details, see Documentation/core-api/protection-keys.rst
> +
> +	  If unsure, say y.
> +
> +endmenu # "ARMv8.9 architectural features"

I agree with Mark, we typically leave the Kconfig option towards the end
of the series.

> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 646591c67e7a..00b6d516ed3f 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -2731,6 +2731,15 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
>  		.matches = has_cpuid_feature,
>  		ARM64_CPUID_FIELDS(ID_AA64MMFR2_EL1, EVT, IMP)
>  	},
> +#ifdef CONFIG_ARM64_POE
> +	{
> +		.desc = "Stage-1 Permission Overlay Extension (S1POE)",
> +		.capability = ARM64_HAS_S1POE,
> +		.type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
> +		.matches = has_cpuid_feature,
> +		ARM64_CPUID_FIELDS(ID_AA64MMFR3_EL1, S1POE, IMP)
> +	},
> +#endif

Keeping the #ifdef here is ok, it won't be defined at this point.

-- 
Catalin