linux-kernel - Re: [PATCH 04/11] arm64/cpufeature: add ARMv8.3 id

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Message-ID: <915a28c3-ec4d-2c19-17d1-ed47a6396ff9@arm.com>
Date:   Mon, 24 Jul 2017 11:54:58 +0100
From:   Suzuki K Poulose <Suzuki.Poulose@....com>
To:     Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     arnd@...db.de, catalin.marinas@....com,
        christoffer.dall@...aro.org, Dave.Martin@....com,
        jiong.wang@....com, kvmarm@...ts.cs.columbia.edu,
        linux-arch@...r.kernel.org, marc.zyngier@....com,
        will.deacon@....com, yao.qi@....com, linux-kernel@...r.kernel.org,
        kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH 04/11] arm64/cpufeature: add ARMv8.3 id_aa64isar1 bits

On 19/07/17 17:01, Mark Rutland wrote:
> From ARMv8.3 onwards, ID_AA64ISAR1 is no longer entirely RES0, and now
> has four fields describing the presence of pointer authentication
> functionality:
>
> * APA - address authentication present, using an architected algorithm
> * API - address authentication present, using an IMP DEF algorithm
> * GPA - generic authentication present, using an architected algorithm
> * GPI - generic authentication present, using an IMP DEF algoithm
>
> This patch adds the requisite definitions so that we can identify the
> presence of this functionality. For the timebeing, the features are
> hidden from userspace.
>
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Suzuki K Poulose <suzuki.poulose@....com>
> ---
>  arch/arm64/kernel/cpufeature.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 9f9e0064..b23ad83 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -120,7 +120,11 @@ static int __init register_cpu_hwcaps_dumper(void)
>  	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_LRCPC_SHIFT, 4, 0),
>  	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_FCMA_SHIFT, 4, 0),
>  	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_JSCVT_SHIFT, 4, 0),
> -	ARM64_FTR_END,
> +	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_GPI_SHIFT, 4, 0),
> +	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_GPA_SHIFT, 4, 0),
> +	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_API_SHIFT, 4, 0),
> +	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, ID_AA64ISAR1_APA_SHIFT, 4, 0),
> +	ARM64_FTR_END
>  };

minor nit: Could we keep the fields in the order of their positions in the register ?

With that,

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