linux-kernel - Re: [PATCH v5 13/21] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line

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Date:   Mon, 25 Jan 2021 13:15:47 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Marc Zyngier <maz@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        David Brazdil <dbrazdil@...gle.com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Jing Zhang <jingzhangos@...gle.com>,
        Ajay Patil <pajay@....qualcomm.com>,
        Prasad Sodagudi <psodagud@...eaurora.org>,
        Srinivas Ramana <sramana@...eaurora.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v5 13/21] arm64: Allow ID_AA64MMFR1_EL1.VH to be
 overridden from the command line

On 1/25/21 10:50 AM, Marc Zyngier wrote:
> As we want to be able to disable VHE at runtime, let's match
> "id_aa64mmfr1.vh=" from the command line as an override.
> This doesn't have much effect yet as our boot code doesn't look
> at the cpufeature, but only at the HW registers.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> Acked-by: David Brazdil <dbrazdil@...gle.com>
> ---
>   arch/arm64/include/asm/cpufeature.h |  2 ++
>   arch/arm64/kernel/cpufeature.c      |  5 ++++-
>   arch/arm64/kernel/idreg-override.c  | 11 +++++++++++
>   3 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index 4179cfc8ed57..b0ed37da4067 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -818,6 +818,8 @@ static inline unsigned int get_vmid_bits(u64 mmfr1)
>   	return 8;
>   }
>   
> +extern struct arm64_ftr_override id_aa64mmfr1_override;
> +
>   u32 get_kvm_ipa_limit(void);
>   void dump_cpu_features(void);
>   
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 4b84a1e1dc51..c1d6712c4249 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -557,6 +557,8 @@ static const struct arm64_ftr_bits ftr_raz[] = {
>   
>   #define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, &no_override)
>   
> +struct arm64_ftr_override id_aa64mmfr1_override;

Does this need to be ro_after_init ?

Otherwise, looks good to me:

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