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Message-ID: <20190923160710.GC10192@arrakis.emea.arm.com>
Date: Mon, 23 Sep 2019 17:07:11 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Jia He <justin.he@....com>
Cc: Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
James Morse <james.morse@....com>,
Marc Zyngier <maz@...nel.org>,
Matthew Wilcox <willy@...radead.org>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, Suzuki Poulose <Suzuki.Poulose@....com>,
Punit Agrawal <punitagrawal@...il.com>,
Anshuman Khandual <anshuman.khandual@....com>,
Alex Van Brunt <avanbrunt@...dia.com>,
Robin Murphy <robin.murphy@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Jérôme Glisse <jglisse@...hat.com>,
Ralph Campbell <rcampbell@...dia.com>, hejianet@...il.com,
Kaly Xin <Kaly.Xin@....com>, nd@....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@...el.com>
> Suggested-by: Suzuki Poulose <Suzuki.Poulose@....com>
> Signed-off-by: Jia He <justin.he@....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".
> +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@....com>
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