Re: [PATCH 1/2] arm64: mte-kasan: Use IS_ENABLED() rather than ALTERNATIVE() 'cfg' parameter

[Vladimir Murzin <vladimir.murzin@arm.com>]

On 9/2/26 12:32, Mark Rutland wrote:
> The ALTERNATIVE() macro accepts an optional 'cfg' parameter, which
> accepts a CONFIG_* symbol. Where a CONFIG_* symbol is provided, but is
> not selected, the ALTERNATIVE() macro will expand to nothing.
> 
> It would be nicer overall to remove the 'cfg' parameter and to have an
> explicit check for 'cfg' outside of the asm() block. This is clearer to
> a reader, and permits the compiler to elide the asm() block when 'cfg'
> is not selected.
> 
> In the mte-kasan code, replace the usage of the 'cfg' parameter with an
> explicit IS_ENABLED() check.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: James Morse <james.morse@arm.com>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Will Deacon <will@kernel.org>
> ---
>  arch/arm64/include/asm/mte-kasan.h | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/mte-kasan.h b/arch/arm64/include/asm/mte-kasan.h
> index 3521392719189..de910f1c19e1b 100644
> --- a/arch/arm64/include/asm/mte-kasan.h
> +++ b/arch/arm64/include/asm/mte-kasan.h
> @@ -53,14 +53,16 @@ static inline bool system_uses_mte_async_or_asymm_mode(void)
>   */
>  static inline void mte_disable_tco(void)
>  {
> -	asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(0),
> -				 ARM64_MTE, CONFIG_KASAN_HW_TAGS));
> +	if (!IS_ENABLED(CONFIG_KASAN_HW_TAGS))
> +		return;
> +	asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(0), ARM64_MTE));
>  }
>  
>  static inline void mte_enable_tco(void)
>  {
> -	asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(1),
> -				 ARM64_MTE, CONFIG_KASAN_HW_TAGS));
> +	if (!IS_ENABLED(CONFIG_KASAN_HW_TAGS))
> +		return;
> +	asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(1), ARM64_MTE));
>  }
>  
>  /*
> -- 2.30.2
> 

Looks reasonable, FWIW

Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>