linux-kernel - Re: [PATCH] arm64: Check for errata before evaluating cpu features

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Message-ID: <aea2daa9-40ef-2066-0da9-0770c3c50dfb@arm.com>
Date:   Wed, 25 Jul 2018 09:51:53 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Dirk Mueller <dmueller@...e.com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>, Alex Graf <agraf@...e.de>,
        Dave Martin <Dave.Martin@....com>,
        Marc Zyngier <marc.zyngier@....com>
Subject: Re: [PATCH] arm64: Check for errata before evaluating cpu features

On 07/25/2018 09:35 AM, Dirk Mueller wrote:
> Since commit d3aec8a28be3b8 ("arm64: capabilities: Restrict KPTI
> detection to boot-time CPUs") we rely on errata flags being already
> populated during feature enumeration. The order of errata and
> features was flipped as part of commit ed478b3f9e4a ("arm64:
> capabilities: Group handling of features and errata workarounds").
> 
> Return to the orginal order of errata and feature evaluation to
> ensure errata flags are present during feature evaluation.
> 
> Fixes: d3aec8a28be3b8 ("arm64: capabilities: Restrict KPTI
> detection to boot-time CPUs")
> CC: Suzuki K Poulose <suzuki.poulose@....com>
> CC: Marc Zyngier <marc.zyngier@....com>
> Signed-off-by: Dirk Mueller <dmueller@...e.com>

It would be good to add "Fixes: ed478b3f9e4a" (instead), just to make
sure this gets fixed everywhere the original problem appears.

> ---
>   arch/arm64/kernel/cpufeature.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index f24892a40d2c..c6d80743f4ed 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1351,9 +1351,9 @@ static void __update_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
>   
>   static void update_cpu_capabilities(u16 scope_mask)
>   {
> -	__update_cpu_capabilities(arm64_features, scope_mask, "detected:");
>   	__update_cpu_capabilities(arm64_errata, scope_mask,
>   				  "enabling workaround for");
> +	__update_cpu_capabilities(arm64_features, scope_mask, "detected:");
>   }
>   
>   static int __enable_cpu_capability(void *arg)
> @@ -1408,8 +1408,8 @@ __enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
>   
>   static void __init enable_cpu_capabilities(u16 scope_mask)
>   {
> -	__enable_cpu_capabilities(arm64_features, scope_mask);
>   	__enable_cpu_capabilities(arm64_errata, scope_mask);
> +	__enable_cpu_capabilities(arm64_features, scope_mask);

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