From: Catalin Marinas <catalin.marinas@arm•com>
To: Jia He <justin.he@arm•com>
Cc: Mark Rutland <mark.rutland@arm•com>, Kaly Xin <Kaly.Xin@arm•com>,
Suzuki Poulose <Suzuki.Poulose@arm•com>,
Marc Zyngier <maz@kernel•org>,
x86@kernel•org, hejianet@gmail•com, linux-kernel@vger•kernel.org,
Matthew Wilcox <willy@infradead•org>,
linux-mm@kvack•org, James Morse <james.morse@arm•com>,
linux-arm-kernel@lists•infradead.org,
"H. Peter Anvin" <hpa@zytor•com>, Borislav Petkov <bp@alien8•de>,
Thomas Gleixner <tglx@linutronix•de>,
nd@arm•com, Will Deacon <will@kernel•org>,
Andrew Morton <akpm@linux-foundation•org>,
"Kirill A. Shutemov" <kirill.shutemov@linux•intel.com>
Subject: Re: [PATCH v11 1/4] arm64: cpufeature: introduce helper cpu_has_hw_af()
Date: Thu, 10 Oct 2019 17:43:12 +0100 [thread overview]
Message-ID: <20191010164312.GB40923@arrakis.emea.arm.com> (raw)
In-Reply-To: <20191009084246.123354-2-justin.he@arm.com>
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@arm•com>
> Suggested-by: Suzuki Poulose <Suzuki.Poulose@arm•com>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm•com>
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
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next prev parent reply other threads:[~2019-10-10 16:43 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 8:42 [PATCH v11 0/4] fix double page fault in cow_user_page for pfn mapping Jia He
2019-10-09 8:42 ` [PATCH v11 1/4] arm64: cpufeature: introduce helper cpu_has_hw_af() Jia He
2019-10-10 16:43 ` Catalin Marinas [this message]
2019-10-11 1:16 ` Justin He (Arm Technology China)
2019-10-11 10:38 ` Catalin Marinas
2019-10-11 13:51 ` Justin He (Arm Technology China)
2019-10-09 8:42 ` [PATCH v11 2/4] arm64: mm: implement arch_faults_on_old_pte() on arm64 Jia He
2019-10-09 8:42 ` [PATCH v11 3/4] x86/mm: implement arch_faults_on_old_pte() stub on x86 Jia He
2019-10-09 8:42 ` [PATCH v11 4/4] mm: fix double page fault on arm64 if PTE_AF is cleared Jia He
2019-10-10 16:45 ` Catalin Marinas
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