From: "Justin He (Arm Technology China)" <Justin.He@arm.com>
To: Catalin Marinas <Catalin.Marinas@arm.com>
Cc: Will Deacon <will@kernel.org>,
Mark Rutland <Mark.Rutland@arm.com>,
James Morse <James.Morse@arm.com>, Marc Zyngier <maz@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Suzuki Poulose <Suzuki.Poulose@arm.com>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
"x86@kernel.org" <x86@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
"hejianet@gmail.com" <hejianet@gmail.com>,
"Kaly Xin (Arm Technology China)" <Kaly.Xin@arm.com>,
nd <nd@arm.com>
Subject: RE: [PATCH v11 1/4] arm64: cpufeature: introduce helper cpu_has_hw_af()
Date: Fri, 11 Oct 2019 01:16:36 +0000 [thread overview]
Message-ID: <DB7PR08MB3082E71F1FF5FE8462F88B8BF7970@DB7PR08MB3082.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <20191010164312.GB40923@arrakis.emea.arm.com>
Hi Catalin
> -----Original Message-----
> From: Catalin Marinas <catalin.marinas@arm.com>
> Sent: Friday, October 11, 2019 12:43 AM
> To: Justin He (Arm Technology China) <Justin.He@arm.com>
> Cc: Will Deacon <will@kernel.org>; Mark Rutland
> <Mark.Rutland@arm.com>; James Morse <James.Morse@arm.com>; Marc
> Zyngier <maz@kernel.org>; Matthew Wilcox <willy@infradead.org>; Kirill A.
> Shutemov <kirill.shutemov@linux.intel.com>; linux-arm-
> kernel@lists.infradead.org; linux-kernel@vger.kernel.org; linux-
> mm@kvack.org; Suzuki Poulose <Suzuki.Poulose@arm.com>; Borislav
> Petkov <bp@alien8.de>; H. Peter Anvin <hpa@zytor.com>; x86@kernel.org;
> Thomas Gleixner <tglx@linutronix.de>; Andrew Morton <akpm@linux-
> foundation.org>; hejianet@gmail.com; Kaly Xin (Arm Technology China)
> <Kaly.Xin@arm.com>; nd <nd@arm.com>
> Subject: Re: [PATCH v11 1/4] arm64: cpufeature: introduce helper
> cpu_has_hw_af()
>
> 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.
Sorry about that.
>
> > 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:
Okay
>
> 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.
But cpuid_feature_extract_unsigned_field has the return type "unsigned int" [1]
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/include/asm/cpufeature.h#n444
>
> Anyway, apart from these nitpicks, the patch is fine you can keep my
> reviewed-by.
Thanks 😉
>
> If later we noticed a potential performance issue on this path, we can
> turn it into a static label as with other CPU features.
Okay
--
Cheers,
Justin (Jia He)
next prev parent reply other threads:[~2019-10-11 1:17 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
2019-10-11 1:16 ` Justin He (Arm Technology China) [this message]
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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