Hi Catalin > -----Original Message----- > From: Catalin Marinas <catalin.mari...@arm.com> > Sent: Friday, October 11, 2019 12:43 AM > To: Justin He (Arm Technology China) <justin...@arm.com> > Cc: Will Deacon <w...@kernel.org>; Mark Rutland > <mark.rutl...@arm.com>; James Morse <james.mo...@arm.com>; Marc > Zyngier <m...@kernel.org>; Matthew Wilcox <wi...@infradead.org>; Kirill A. > Shutemov <kirill.shute...@linux.intel.com>; linux-arm- > ker...@lists.infradead.org; linux-kernel@vger.kernel.org; linux- > m...@kvack.org; Suzuki Poulose <suzuki.poul...@arm.com>; Borislav > Petkov <b...@alien8.de>; H. Peter Anvin <h...@zytor.com>; x...@kernel.org; > Thomas Gleixner <t...@linutronix.de>; Andrew Morton <akpm@linux- > foundation.org>; hejia...@gmail.com; Kaly Xin (Arm Technology China) > <kaly....@arm.com>; nd <n...@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...@arm.com> > > Suggested-by: Suzuki Poulose <suzuki.poul...@arm.com> > > Reviewed-by: Catalin Marinas <catalin.mari...@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)