linux-kernel - Re: [PATCH 1/6] arm64/cpufeature: Introduce ID

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Date:   Thu, 9 Apr 2020 13:54:31 +0100
From:   Will Deacon <will@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mark Rutland <mark.rutland@....com>,
        kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] arm64/cpufeature: Introduce ID_PFR2 CPU register

On Tue, Jan 28, 2020 at 06:09:04PM +0530, Anshuman Khandual wrote:
> This adds basic building blocks required for ID_PFR2 CPU register which
> provides information about the AArch32 programmers model which must be
> interpreted along with ID_PFR0 and ID_PFR1 CPU registers.
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: James Morse <james.morse@....com>
> Cc: Suzuki K Poulose <suzuki.poulose@....com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: kvmarm@...ts.cs.columbia.edu
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
>  arch/arm64/include/asm/cpu.h    |  1 +
>  arch/arm64/include/asm/sysreg.h |  4 ++++
>  arch/arm64/kernel/cpufeature.c  | 11 +++++++++++
>  arch/arm64/kernel/cpuinfo.c     |  1 +
>  arch/arm64/kvm/sys_regs.c       |  2 +-
>  5 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/cpu.h b/arch/arm64/include/asm/cpu.h
> index b4a40535a3d8..464e828a994d 100644
> --- a/arch/arm64/include/asm/cpu.h
> +++ b/arch/arm64/include/asm/cpu.h
> @@ -46,6 +46,7 @@ struct cpuinfo_arm64 {
>  	u32		reg_id_mmfr3;
>  	u32		reg_id_pfr0;
>  	u32		reg_id_pfr1;
> +	u32		reg_id_pfr2;
>  
>  	u32		reg_mvfr0;
>  	u32		reg_mvfr1;
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index b91570ff9db1..054aab7ebf1b 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -151,6 +151,7 @@
>  #define SYS_MVFR0_EL1			sys_reg(3, 0, 0, 3, 0)
>  #define SYS_MVFR1_EL1			sys_reg(3, 0, 0, 3, 1)
>  #define SYS_MVFR2_EL1			sys_reg(3, 0, 0, 3, 2)
> +#define SYS_ID_PFR2_EL1			sys_reg(3, 0, 0, 3, 4)
>  
>  #define SYS_ID_AA64PFR0_EL1		sys_reg(3, 0, 0, 4, 0)
>  #define SYS_ID_AA64PFR1_EL1		sys_reg(3, 0, 0, 4, 1)
> @@ -717,6 +718,9 @@
>  #define ID_ISAR6_DP_SHIFT		4
>  #define ID_ISAR6_JSCVT_SHIFT		0
>  
> +#define ID_PFR2_SSBS_SHIFT		4
> +#define ID_PFR2_CSV3_SHIFT		0
> +
>  #define MVFR0_FPROUND_SHIFT		28
>  #define MVFR0_FPSHVEC_SHIFT		24
>  #define MVFR0_FPSQRT_SHIFT		20
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 0b6715625cf6..c1e837fc8f97 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -348,6 +348,12 @@ static const struct arm64_ftr_bits ftr_id_pfr0[] = {
>  	ARM64_FTR_END,
>  };
>  
> +static const struct arm64_ftr_bits ftr_id_pfr2[] = {
> +	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_PFR2_SSBS_SHIFT, 4, 0),
> +	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_PFR2_CSV3_SHIFT, 4, 0),

Why is CSV3 strict here, but not when we see if in aa64pfr0? I think it
should be non-strict in both cases.

Will