linux-kernel - Re: [PATCH v4 2/8] arm64: irqflags: Pass flags as readonly operand to restore instruction

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Message-ID: <20190611124641.GB29008@lakrids.cambridge.arm.com>
Date:   Tue, 11 Jun 2019 13:46:42 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Julien Thierry <julien.thierry@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        rostedt@...dmis.org, marc.zyngier@....com, yuzenghui@...wei.com,
        wanghaibin.wang@...wei.com, james.morse@....com,
        will.deacon@....com, catalin.marinas@....com, liwei391@...wei.com
Subject: Re: [PATCH v4 2/8] arm64: irqflags: Pass flags as readonly operand
 to restore instruction

On Tue, Jun 11, 2019 at 10:38:07AM +0100, Julien Thierry wrote:
> Flags are only read by the instructions doing the irqflags restore
> operation. Pass the operand as read only to the asm inline instead of
> read-write.
> 
> Signed-off-by: Julien Thierry <julien.thierry@....com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>

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

Mark.

> ---
>  arch/arm64/include/asm/irqflags.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/irqflags.h b/arch/arm64/include/asm/irqflags.h
> index 62996318..9c93152 100644
> --- a/arch/arm64/include/asm/irqflags.h
> +++ b/arch/arm64/include/asm/irqflags.h
> @@ -119,8 +119,8 @@ static inline void arch_local_irq_restore(unsigned long flags)
>  			__msr_s(SYS_ICC_PMR_EL1, "%0")
>  			"dsb	sy",
>  			ARM64_HAS_IRQ_PRIO_MASKING)
> -		: "+r" (flags)
>  		:
> +		: "r" (flags)
>  		: "memory");
>  }
> 
> --
> 1.9.1