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From: Catalin Marinas <catalin.marinas@arm.com>
To: Alexander Kuleshov <kuleshovmail@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/3] arm64/cpufeature.h: Add macros for a cpu features testing
Date: Fri, 4 Sep 2015 12:25:56 +0100	[thread overview]
Message-ID: <20150904112555.GB17253@e104818-lin.cambridge.arm.com> (raw)
In-Reply-To: <1441303911-9421-1-git-send-email-kuleshovmail@gmail.com>

On Fri, Sep 04, 2015 at 12:11:51AM +0600, Alexander Kuleshov wrote:
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -28,7 +28,50 @@
>  
>  #define ARM64_NCAPS				4
>  
> +/*
> + * ID_AA64ISAR0_EL1 AES, bits [7:4]
> + */
> +#define ID_AA64ISAR0_EL1_AES_MASK	4
> +#define ID_AA64ISAR0_EL1_AES(feature)	\
> +	(((feature >> ID_AA64ISAR0_EL1_AES_MASK) & 0xf) & 1UL)

This looks more like a shift than a mask. I don't think it's worth
defining another macro for the shift.

> +#define ID_AA64ISAR0_EL1_PMULL(feature)	\
> +	(((feature >> ID_AA64ISAR0_EL1_AES_MASK) & 0xf) & 2UL)

I'm not against some clean-up here but I think you break the original
logic. AES and PMULL are not exclusive, the latter implies the former
but the way you check here is just individual bits. These id fields are
meant to be treated as 4-bit signed values, so if AES means >= 1, PMULL
means >= 2. We have a cpuid_feature_extract_field() (in linux-next and
about to go in 4.3-rc1), so use this one for extracting the signed 4-bit
field.

-- 
Catalin

WARNING: multiple messages have this Message-ID (diff)
From: catalin.marinas@arm.com (Catalin Marinas)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/3] arm64/cpufeature.h: Add macros for a cpu features testing
Date: Fri, 4 Sep 2015 12:25:56 +0100	[thread overview]
Message-ID: <20150904112555.GB17253@e104818-lin.cambridge.arm.com> (raw)
In-Reply-To: <1441303911-9421-1-git-send-email-kuleshovmail@gmail.com>

On Fri, Sep 04, 2015 at 12:11:51AM +0600, Alexander Kuleshov wrote:
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -28,7 +28,50 @@
>  
>  #define ARM64_NCAPS				4
>  
> +/*
> + * ID_AA64ISAR0_EL1 AES, bits [7:4]
> + */
> +#define ID_AA64ISAR0_EL1_AES_MASK	4
> +#define ID_AA64ISAR0_EL1_AES(feature)	\
> +	(((feature >> ID_AA64ISAR0_EL1_AES_MASK) & 0xf) & 1UL)

This looks more like a shift than a mask. I don't think it's worth
defining another macro for the shift.

> +#define ID_AA64ISAR0_EL1_PMULL(feature)	\
> +	(((feature >> ID_AA64ISAR0_EL1_AES_MASK) & 0xf) & 2UL)

I'm not against some clean-up here but I think you break the original
logic. AES and PMULL are not exclusive, the latter implies the former
but the way you check here is just individual bits. These id fields are
meant to be treated as 4-bit signed values, so if AES means >= 1, PMULL
means >= 2. We have a cpuid_feature_extract_field() (in linux-next and
about to go in 4.3-rc1), so use this one for extracting the signed 4-bit
field.

-- 
Catalin

  parent reply	other threads:[~2015-09-04 11:26 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-03 18:11 [PATCH 1/3] arm64/cpufeature.h: Add macros for a cpu features testing Alexander Kuleshov
2015-09-03 18:11 ` Alexander Kuleshov
2015-09-03 18:12 ` [PATCH 2/3] arm64/setup: Use ID_AA64ISAR0_EL1_.* macros Alexander Kuleshov
2015-09-03 18:12   ` Alexander Kuleshov
2015-09-04 11:26   ` Catalin Marinas
2015-09-04 11:26     ` Catalin Marinas
2016-11-07 16:30   ` Suzuki K Poulose
2016-11-07 16:30     ` Suzuki K Poulose
2015-09-03 18:12 ` [PATCH 3/3] arm64/fpsimd: Use ID_AA64PFR0_EL1_.* macros Alexander Kuleshov
2015-09-03 18:12   ` Alexander Kuleshov
2016-11-07 16:31   ` Suzuki K Poulose
2016-11-07 16:31     ` Suzuki K Poulose
2015-09-04 11:25 ` Catalin Marinas [this message]
2015-09-04 11:25   ` [PATCH 1/3] arm64/cpufeature.h: Add macros for a cpu features testing Catalin Marinas
2015-09-04 12:00 ` Suzuki K. Poulose
2015-09-04 12:00   ` Suzuki K. Poulose
2015-09-04 12:19   ` Alexander Kuleshov
2015-09-04 12:19     ` Alexander Kuleshov
2015-09-16 14:48     ` Suzuki K. Poulose
2015-09-16 14:48       ` Suzuki K. Poulose

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