Messages in this thread | | | From | "Justin He (Arm Technology China)" <> | Subject | RE: [PATCH v8 1/3] arm64: cpufeature: introduce helper cpu_has_hw_af() | Date | Tue, 24 Sep 2019 01:50:24 +0000 |
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Hi Catalin
> -----Original Message----- > From: Catalin Marinas <catalin.marinas@arm.com> > Sent: 2019年9月24日 0:07 > 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>; Punit > Agrawal <punitagrawal@gmail.com>; Anshuman Khandual > <Anshuman.Khandual@arm.com>; Alex Van Brunt > <avanbrunt@nvidia.com>; Robin Murphy <Robin.Murphy@arm.com>; > Thomas Gleixner <tglx@linutronix.de>; Andrew Morton <akpm@linux- > foundation.org>; Jérôme Glisse <jglisse@redhat.com>; Ralph Campbell > <rcampbell@nvidia.com>; hejianet@gmail.com; Kaly Xin (Arm Technology > China) <Kaly.Xin@arm.com>; nd <nd@arm.com> > Subject: Re: [PATCH v8 1/3] arm64: cpufeature: introduce helper > cpu_has_hw_af() > > On Sat, Sep 21, 2019 at 09:50:52PM +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 new helper cpu_has_hw_af(). > > > > Reported-by: kbuild test robot <lkp@intel.com> > > Suggested-by: Suzuki Poulose <Suzuki.Poulose@arm.com> > > Signed-off-by: Jia He <justin.he@arm.com> > > --- > > arch/arm64/include/asm/cpufeature.h | 10 ++++++++++ > > 1 file changed, 10 insertions(+) > > > > diff --git a/arch/arm64/include/asm/cpufeature.h > b/arch/arm64/include/asm/cpufeature.h > > index c96ffa4722d3..46caf934ba4e 100644 > > --- a/arch/arm64/include/asm/cpufeature.h > > +++ b/arch/arm64/include/asm/cpufeature.h > > @@ -667,6 +667,16 @@ static inline u32 > id_aa64mmfr0_parange_to_phys_shift(int parange) > > default: return CONFIG_ARM64_PA_BITS; > > } > > } > > + > > +/* Decouple AF from AFDBM. */ > > We could do with a better comment here or just remove it altogether. The > aim of the patch was to decouple AF check from the AF+DBM but the > comment here should describe what the function does. Maybe something > like: "Check whether hardware update of the Access flag is supported". >
Okay, I will update it
-- Cheers, Justin (Jia He)
> > +static inline bool cpu_has_hw_af(void) > > +{ > > + if (IS_ENABLED(CONFIG_ARM64_HW_AFDBM)) > > + return read_cpuid(ID_AA64MMFR1_EL1) & 0xf; > > + > > + return false; > > +} > > Other than the comment above, > > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
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