On Wed, Oct 09, 2019 at 04:42:43PM +0800, Jia He wrote:
> We unconditionally set the HW_AFDBM capability and only enable it on
> CPUs which really have the feature. But sometimes we need to know
> whether this cpu has the capability of HW AF. So decouple AF from
> DBM by a new helper cpu_has_hw_af().
>
> Signed-off-by: Jia He <justin.he@xxxxxxx>
> Suggested-by: Suzuki Poulose <Suzuki.Poulose@xxxxxxx>
> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
I don't think I reviewed this version of the patch.
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index 9cde5d2e768f..1a95396ea5c8 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -659,6 +659,20 @@ static inline u32 id_aa64mmfr0_parange_to_phys_shift(int parange)
> default: return CONFIG_ARM64_PA_BITS;
> }
> }
> +
> +/* Check whether hardware update of the Access flag is supported */
> +static inline bool cpu_has_hw_af(void)
> +{
> + if (IS_ENABLED(CONFIG_ARM64_HW_AFDBM)) {
Please just return early here to avoid unnecessary indentation:
if (!IS_ENABLED(CONFIG_ARM64_HW_AFDBM))
return false;
> + u64 mmfr1 = read_cpuid(ID_AA64MMFR1_EL1);
> +
> + return !!cpuid_feature_extract_unsigned_field(mmfr1,
> + ID_AA64MMFR1_HADBS_SHIFT);
No need for !!, the return type is a bool already.
Anyway, apart from these nitpicks, the patch is fine you can keep my
reviewed-by.
If later we noticed a potential performance issue on this path, we can
turn it into a static label as with other CPU features.
--
Catalin
