linux-kernel - Re: [PATCH 4/8] arm64: cpufeature: Remove redundant call to id_aa64pfr0_32bit

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Message-ID: <8f911640-8b7d-bb6f-2b76-67dd0d259b75@arm.com>
Date:   Wed, 15 Apr 2020 11:25:35 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     will@...nel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu
Cc:     linux-kernel@...r.kernel.org, mark.rutland@....com, maz@...nel.org,
        anshuman.khandual@....com, catalin.marinas@....com,
        saiprakash.ranjan@...eaurora.org, dianders@...omium.org,
        kernel-team@...roid.com
Subject: Re: [PATCH 4/8] arm64: cpufeature: Remove redundant call to
 id_aa64pfr0_32bit_el0()

On 04/14/2020 10:31 PM, Will Deacon wrote:
> There's no need to call id_aa64pfr0_32bit_el0() twice because the
> sanitised value of ID_AA64PFR0_EL1 has already been updated for the CPU
> being onlined.
> 
> Remove the redundant function call.
> 
> Signed-off-by: Will Deacon <will@...nel.org>

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

> ---
>   arch/arm64/kernel/cpufeature.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 838fe5cc8d7e..7dfcdd9e75c1 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -792,9 +792,7 @@ void update_cpu_features(int cpu,
>   	 * If we have AArch32, we care about 32-bit features for compat.
>   	 * If the system doesn't support AArch32, don't update them.
>   	 */
> -	if (id_aa64pfr0_32bit_el0(read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1)) &&
> -		id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0)) {
> -
> +	if (id_aa64pfr0_32bit_el0(read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1))) {
>   		taint |= check_update_ftr_reg(SYS_ID_DFR0_EL1, cpu,
>   					info->reg_id_dfr0, boot->reg_id_dfr0);
>   		taint |= check_update_ftr_reg(SYS_ID_ISAR0_EL1, cpu,
>