linux-kernel - Re: linux-next: manual merge of the kvm-arm tree with the arm64 tree

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Message-ID: <ZdN1LGKRwcwfhvKB@FVFF77S0Q05N>
Date: Mon, 19 Feb 2024 15:35:08 +0000
From: Mark Rutland <mark.rutland@....com>
To: Marc Zyngier <maz@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Christoffer Dall <cdall@...columbia.edu>,
	Will Deacon <will@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Next Mailing List <linux-next@...r.kernel.org>,
	Oliver Upton <oliver.upton@...ux.dev>
Subject: Re: linux-next: manual merge of the kvm-arm tree with the arm64 tree

On Mon, Feb 19, 2024 at 03:22:14PM +0000, Marc Zyngier wrote:
> From f24638a5f41424faf47f3d9035e6dcbd3800fcb6 Mon Sep 17 00:00:00 2001
> From: Marc Zyngier <maz@...nel.org>
> Date: Mon, 19 Feb 2024 15:13:22 +0000
> Subject: [PATCH] arm64: Use Signed/Unsigned enums for TGRAN{4,16,64} and
>  VARange
> 
> Open-coding the feature matching parameters for LVA/LVA2 leads to
> issues with upcoming changes to the cpufeature code.
> 
> By making TGRAN{4,16,64} and VARange signed/unsigned as per the
> architecture, we can use the existing macros, making the feature
> match robust against those changes.
> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>

I think this is the right thing to do; the patch itself looks good to me, so
FWIW:

Acked-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  arch/arm64/kernel/cpufeature.c | 15 +++------------
>  arch/arm64/tools/sysreg        |  8 ++++----
>  2 files changed, 7 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 8f9665e8774b..2119e9dd0c4e 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -2791,24 +2791,15 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
>  		.capability = ARM64_HAS_VA52,
>  		.type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
>  		.matches = has_cpuid_feature,
> -		.field_width = 4,
>  #ifdef CONFIG_ARM64_64K_PAGES
>  		.desc = "52-bit Virtual Addressing (LVA)",
> -		.sign = FTR_SIGNED,
> -		.sys_reg = SYS_ID_AA64MMFR2_EL1,
> -		.field_pos = ID_AA64MMFR2_EL1_VARange_SHIFT,
> -		.min_field_value = ID_AA64MMFR2_EL1_VARange_52,
> +		ARM64_CPUID_FIELDS(ID_AA64MMFR2_EL1, VARange, 52)
>  #else
>  		.desc = "52-bit Virtual Addressing (LPA2)",
> -		.sys_reg = SYS_ID_AA64MMFR0_EL1,
>  #ifdef CONFIG_ARM64_4K_PAGES
> -		.sign = FTR_SIGNED,
> -		.field_pos = ID_AA64MMFR0_EL1_TGRAN4_SHIFT,
> -		.min_field_value = ID_AA64MMFR0_EL1_TGRAN4_52_BIT,
> +		ARM64_CPUID_FIELDS(ID_AA64MMFR0_EL1, TGRAN4, 52_BIT)
>  #else
> -		.sign = FTR_UNSIGNED,
> -		.field_pos = ID_AA64MMFR0_EL1_TGRAN16_SHIFT,
> -		.min_field_value = ID_AA64MMFR0_EL1_TGRAN16_52_BIT,
> +		ARM64_CPUID_FIELDS(ID_AA64MMFR0_EL1, TGRAN16, 52_BIT)
>  #endif
>  #endif
>  	},
> diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
> index fa3fe0856880..670a33fca3bc 100644
> --- a/arch/arm64/tools/sysreg
> +++ b/arch/arm64/tools/sysreg
> @@ -1540,16 +1540,16 @@ Enum	35:32	TGRAN16_2
>  	0b0010	IMP
>  	0b0011	52_BIT
>  EndEnum
> -Enum	31:28	TGRAN4
> +SignedEnum	31:28	TGRAN4
>  	0b0000	IMP
>  	0b0001	52_BIT
>  	0b1111	NI
>  EndEnum
> -Enum	27:24	TGRAN64
> +SignedEnum	27:24	TGRAN64
>  	0b0000	IMP
>  	0b1111	NI
>  EndEnum
> -Enum	23:20	TGRAN16
> +UnsignedEnum	23:20	TGRAN16
>  	0b0000	NI
>  	0b0001	IMP
>  	0b0010	52_BIT
> @@ -1697,7 +1697,7 @@ Enum	23:20	CCIDX
>  	0b0000	32
>  	0b0001	64
>  EndEnum
> -Enum	19:16	VARange
> +UnsignedEnum	19:16	VARange
>  	0b0000	48
>  	0b0001	52
>  EndEnum
> -- 
> 2.39.2
> 
> 
> -- 
> Without deviation from the norm, progress is not possible.