Re: [PATCH v4 3/5] arm64: Add support for FEAT_HAFT

[Catalin Marinas <catalin.marinas@arm.com>]

On Sat, Nov 02, 2024 at 06:42:33PM +0800, Yicong Yang wrote:
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index 3d261cc123c1..ed8c784ca082 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -838,6 +838,12 @@ static inline bool system_supports_poe(void)
>  		alternative_has_cap_unlikely(ARM64_HAS_S1POE);
>  }
>  
> +static inline bool system_supports_haft(void)
> +{
> +	return IS_ENABLED(CONFIG_ARM64_HAFT) &&
> +		cpus_have_final_cap(ARM64_HAFT);
> +}

I'm fine with this approach. If we ever get hardware with mismatched
FEAT_HAFT and some secondary CPUs don't come up, we can revisit.

> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> index ccbae4525891..0bc88df7cb35 100644
> --- a/arch/arm64/mm/proc.S
> +++ b/arch/arm64/mm/proc.S
> @@ -498,6 +498,10 @@ alternative_else_nop_endif
>  	and	x9, x9, ID_AA64MMFR1_EL1_HAFDBS_MASK
>  	cbz	x9, 1f
>  	orr	tcr, tcr, #TCR_HA		// hardware Access flag update
> +
> +#ifdef CONFIG_ARM64_HAFT
> +	orr	tcr2, tcr2, TCR2_EL1x_HAFT
> +#endif /* CONFIG_ARM64_HAFT */
>  1:
>  #endif	/* CONFIG_ARM64_HW_AFDBM */
>  	msr	mair_el1, mair

If you still want #ifdefs, I'd have left it outside the HW_AFDBM. We
already have a dependency in the Kconfig. Anyway, I can fix this up.

I think as an additional patch we can also remove the ID checks for the
tcr bit in tge HW_AFDBM case. But that's unrelated to this series.

-- 
Catalin