Re: [PATCH 1/6] arm64/cpufeature: Introduce ID_PFR2 CPU register

From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-kernel@vger.kernel.org, James Morse <james.morse@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/6] arm64/cpufeature: Introduce ID_PFR2 CPU register
Date: Mon, 13 Apr 2020 09:02:57 +0530	[thread overview]
Message-ID: <8b905244-c296-3859-b515-711550bef3a2@arm.com> (raw)
In-Reply-To: <20200409125431.GB13078@willie-the-truck>

On 04/09/2020 06:24 PM, Will Deacon wrote:
> 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@arm.com>
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Marc Zyngier <maz@kernel.org>
>> Cc: James Morse <james.morse@arm.com>
>> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: kvmarm@lists.cs.columbia.edu
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.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.

Sure, will do.

> 
> Will
> 

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