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From: Catalin Marinas <catalin.marinas@arm.com>
To: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: "Jia He" <justin.he@arm.com>, "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,
	"Punit Agrawal" <punitagrawal@gmail.com>,
	"Anshuman Khandual" <anshuman.khandual@arm.com>,
	"Jun Yao" <yaojun8558363@gmail.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" <Kaly.Xin@arm.com>
Subject: Re: [PATCH v4 1/3] arm64: cpufeature: introduce helper cpu_has_hw_af()
Date: Wed, 18 Sep 2019 17:45:47 +0100	[thread overview]
Message-ID: <20190918164546.GA41588@arrakis.emea.arm.com> (raw)
In-Reply-To: <78881acb-5871-9534-c8cc-6f54937be3fd@arm.com>

On Wed, Sep 18, 2019 at 03:20:41PM +0100, Suzuki K Poulose wrote:
> On 18/09/2019 14:19, Jia He wrote:
> > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> > index c96ffa4722d3..206b6e3954cf 100644
> > --- a/arch/arm64/include/asm/cpufeature.h
> > +++ b/arch/arm64/include/asm/cpufeature.h
> > @@ -390,6 +390,7 @@ extern DECLARE_BITMAP(boot_capabilities, ARM64_NPATCHABLE);
> >   	for_each_set_bit(cap, cpu_hwcaps, ARM64_NCAPS)
> >   bool this_cpu_has_cap(unsigned int cap);
> > +bool cpu_has_hw_af(void);
> >   void cpu_set_feature(unsigned int num);
> >   bool cpu_have_feature(unsigned int num);
> >   unsigned long cpu_get_elf_hwcap(void);
> > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> > index b1fdc486aed8..c5097f58649d 100644
> > --- a/arch/arm64/kernel/cpufeature.c
> > +++ b/arch/arm64/kernel/cpufeature.c
> > @@ -1141,6 +1141,12 @@ static bool has_hw_dbm(const struct arm64_cpu_capabilities *cap,
> >   	return true;
> >   }
> > +/* Decouple AF from AFDBM. */
> > +bool cpu_has_hw_af(void)
> > +{
> Sorry for not having asked this earlier. Are we interested in,
> 
> "whether *this* CPU has AF support ?" or "whether *at least one*
> CPU has the AF support" ? The following code does the former.
> 
> > +	return (read_cpuid(ID_AA64MMFR1_EL1) & 0xf);

In a non-preemptible context, the former is ok (per-CPU).

-- 
Catalin

WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: "Mark Rutland" <mark.rutland@arm.com>,
	"Kaly Xin" <Kaly.Xin@arm.com>,
	"Ralph Campbell" <rcampbell@nvidia.com>,
	"Jia He" <justin.he@arm.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Anshuman Khandual" <anshuman.khandual@arm.com>,
	"Marc Zyngier" <maz@kernel.org>,
	linux-kernel@vger.kernel.org,
	"Matthew Wilcox" <willy@infradead.org>,
	"Jun Yao" <yaojun8558363@gmail.com>,
	linux-mm@kvack.org, "Jérôme Glisse" <jglisse@redhat.com>,
	"James Morse" <james.morse@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	"Punit Agrawal" <punitagrawal@gmail.com>,
	hejianet@gmail.com, "Thomas Gleixner" <tglx@linutronix.de>,
	"Will Deacon" <will@kernel.org>,
	"Alex Van Brunt" <avanbrunt@nvidia.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	"Robin Murphy" <robin.murphy@arm.com>
Subject: Re: [PATCH v4 1/3] arm64: cpufeature: introduce helper cpu_has_hw_af()
Date: Wed, 18 Sep 2019 17:45:47 +0100	[thread overview]
Message-ID: <20190918164546.GA41588@arrakis.emea.arm.com> (raw)
In-Reply-To: <78881acb-5871-9534-c8cc-6f54937be3fd@arm.com>

On Wed, Sep 18, 2019 at 03:20:41PM +0100, Suzuki K Poulose wrote:
> On 18/09/2019 14:19, Jia He wrote:
> > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> > index c96ffa4722d3..206b6e3954cf 100644
> > --- a/arch/arm64/include/asm/cpufeature.h
> > +++ b/arch/arm64/include/asm/cpufeature.h
> > @@ -390,6 +390,7 @@ extern DECLARE_BITMAP(boot_capabilities, ARM64_NPATCHABLE);
> >   	for_each_set_bit(cap, cpu_hwcaps, ARM64_NCAPS)
> >   bool this_cpu_has_cap(unsigned int cap);
> > +bool cpu_has_hw_af(void);
> >   void cpu_set_feature(unsigned int num);
> >   bool cpu_have_feature(unsigned int num);
> >   unsigned long cpu_get_elf_hwcap(void);
> > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> > index b1fdc486aed8..c5097f58649d 100644
> > --- a/arch/arm64/kernel/cpufeature.c
> > +++ b/arch/arm64/kernel/cpufeature.c
> > @@ -1141,6 +1141,12 @@ static bool has_hw_dbm(const struct arm64_cpu_capabilities *cap,
> >   	return true;
> >   }
> > +/* Decouple AF from AFDBM. */
> > +bool cpu_has_hw_af(void)
> > +{
> Sorry for not having asked this earlier. Are we interested in,
> 
> "whether *this* CPU has AF support ?" or "whether *at least one*
> CPU has the AF support" ? The following code does the former.
> 
> > +	return (read_cpuid(ID_AA64MMFR1_EL1) & 0xf);

In a non-preemptible context, the former is ok (per-CPU).

-- 
Catalin

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  reply	other threads:[~2019-09-18 16:45 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-18 13:19 [PATCH v4 0/3] fix double page fault on arm64 Jia He
2019-09-18 13:19 ` Jia He
2019-09-18 13:19 ` [PATCH v4 1/3] arm64: cpufeature: introduce helper cpu_has_hw_af() Jia He
2019-09-18 13:19   ` Jia He
2019-09-18 14:20   ` Matthew Wilcox
2019-09-18 14:20     ` Matthew Wilcox
2019-09-18 16:49     ` Catalin Marinas
2019-09-18 16:49       ` Catalin Marinas
2019-09-18 14:20   ` Suzuki K Poulose
2019-09-18 14:20     ` Suzuki K Poulose
2019-09-18 16:45     ` Catalin Marinas [this message]
2019-09-18 16:45       ` Catalin Marinas
2019-09-19  1:55       ` Justin He (Arm Technology China)
2019-09-19  1:55         ` Justin He (Arm Technology China)
2019-09-18 13:19 ` [PATCH v4 2/3] arm64: mm: implement arch_faults_on_old_pte() on arm64 Jia He
2019-09-18 13:19   ` Jia He
2019-09-18 13:19 ` [PATCH v4 3/3] mm: fix double page fault on arm64 if PTE_AF is cleared Jia He
2019-09-18 13:19   ` Jia He
2019-09-18 14:00   ` Kirill A. Shutemov
2019-09-18 14:00     ` Kirill A. Shutemov
2019-09-18 18:00     ` Catalin Marinas
2019-09-18 18:00       ` Catalin Marinas
2019-09-19 15:00       ` Kirill A. Shutemov
2019-09-19 15:00         ` Kirill A. Shutemov
2019-09-19 15:41         ` Catalin Marinas
2019-09-19 15:41           ` Catalin Marinas
2019-09-19 15:51           ` Kirill A. Shutemov
2019-09-19 15:51             ` Kirill A. Shutemov
2019-09-19  2:16     ` Jia He
2019-09-19  2:16       ` Jia He
2019-09-19 14:57       ` Kirill A. Shutemov
2019-09-19 14:57         ` Kirill A. Shutemov
2019-09-19 15:02         ` Justin He (Arm Technology China)
2019-09-19 15:02           ` Justin He (Arm Technology China)
2019-09-18 19:35   ` kbuild test robot
2019-09-18 19:35     ` kbuild test robot
2019-09-19  1:46     ` Justin He (Arm Technology China)
2019-09-19  1:46       ` Justin He (Arm Technology China)
2019-09-19  1:46       ` Justin He (Arm Technology China)

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