linux-kernel - Re: [PATCH v1 1/4] KVM: arm64: Use macro to replace hard number

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Message-ID: <20190222114013.GB42419@lakrids.cambridge.arm.com>
Date:   Fri, 22 Feb 2019 11:40:13 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Christoffer Dall <christoffer.dall@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        James Morse <james.morse@....com>,
        Andre Przywara <andre.przywara@....com>,
        Jun Yao <yaojun8558363@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/4] KVM: arm64: Use macro to replace hard number

On Fri, Feb 22, 2019 at 04:23:23PM +0800, Leo Yan wrote:
> Use macro for ID_AA64MMFR1_EL1.VH bits shift instead of 8 directly.
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>

It's always nice to get rid of magic numbers, and this is correct
AFAICT. FWIW:

Reviewed-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  arch/arm64/kernel/head.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 4471f570a295..3ac377e9fd28 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -490,7 +490,7 @@ ENTRY(el2_setup)
>  	 * kernel is intended to run at EL2.
>  	 */
>  	mrs	x2, id_aa64mmfr1_el1
> -	ubfx	x2, x2, #8, #4
> +	ubfx	x2, x2, #ID_AA64MMFR1_VHE_SHIFT, #4
>  #else
>  	mov	x2, xzr
>  #endif
> -- 
> 2.17.1
>