linux-kernel - Re: [PATCH v3 3/6] arm64: tlb: Convert the opencoded field modify

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Message-ID: <aAFEOr_PnZRH2ocR@shell.armlinux.org.uk>
Date: Thu, 17 Apr 2025 19:11:06 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Luo Jie <quic_luoj@...cinc.com>
Cc: Yury Norov <yury.norov@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Julia Lawall <Julia.Lawall@...ia.fr>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>, linux-kernel@...r.kernel.org,
	cocci@...ia.fr, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev, andrew@...n.ch, quic_kkumarcs@...cinc.com,
	quic_linchen@...cinc.com, quic_leiwei@...cinc.com,
	quic_suruchia@...cinc.com, quic_pavir@...cinc.com
Subject: Re: [PATCH v3 3/6] arm64: tlb: Convert the opencoded field modify

On Thu, Apr 17, 2025 at 06:47:10PM +0800, Luo Jie wrote:
> Replaced below code with the wrapper FIELD_MODIFY(MASK, &reg, val)
> - reg &= ~MASK;
> - reg |= FIELD_PREP(MASK, val);
> The semantic patch that makes this change is available
> in scripts/coccinelle/misc/field_modify.cocci.
> 
> More information about semantic patching is available at
> https://coccinelle.gitlabpages.inria.fr/website
> 
> Signed-off-by: Luo Jie <quic_luoj@...cinc.com>
> ---
>  arch/arm64/include/asm/tlbflush.h | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> index eba1a98657f1..0d250ef4161c 100644
> --- a/arch/arm64/include/asm/tlbflush.h
> +++ b/arch/arm64/include/asm/tlbflush.h
> @@ -112,8 +112,7 @@ static inline unsigned long get_trans_granule(void)
>  	    level >= 0 && level <= 3) {					\
>  		u64 ttl = level & 3;					\
>  		ttl |= get_trans_granule() << 2;			\
> -		arg &= ~TLBI_TTL_MASK;					\
> -		arg |= FIELD_PREP(TLBI_TTL_MASK, ttl);			\
> +		FIELD_MODIFY(TLBI_TTL_MASK, &arg, ttl);			\

This could equally be:
		arg = u64_replace_bits(arg, ttl, TLBI_TTL_MASK);

which already exists, so doesn't require a new macro to be introduced.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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