linux-kernel - Re: [PATCH V3 06/16] arm64/cpufeature: Introduce ID

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Date:   Tue, 5 May 2020 12:31:54 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Will Deacon <will@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 06/16] arm64/cpufeature: Introduce ID_MMFR5 CPU
 register



On 05/05/2020 02:03 AM, Will Deacon wrote:
> On Sat, May 02, 2020 at 07:03:55PM +0530, Anshuman Khandual wrote:
>> This adds basic building blocks required for ID_MMFR5 CPU register which
>> provides information about the implemented memory model and memory
>> management support in AArch32 state. This is added per ARM DDI 0487F.a
>> specification.
>>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Marc Zyngier <maz@...nel.org>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: James Morse <james.morse@....com>
>> Cc: Suzuki K Poulose <suzuki.poulose@....com>
>> Cc: kvmarm@...ts.cs.columbia.edu
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>>
>> Suggested-by: Will Deacon <will@...nel.org>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
>>  arch/arm64/include/asm/cpu.h    |  1 +
>>  arch/arm64/include/asm/sysreg.h |  3 +++
>>  arch/arm64/kernel/cpufeature.c  | 10 ++++++++++
>>  arch/arm64/kernel/cpuinfo.c     |  1 +
>>  arch/arm64/kvm/sys_regs.c       |  2 +-
>>  5 files changed, 16 insertions(+), 1 deletion(-)
> 
> [...]
> 
>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>> index 2ce952d9668d..c790cc200bb1 100644
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -403,6 +403,11 @@ static const struct arm64_ftr_bits ftr_id_isar4[] = {
>>  	ARM64_FTR_END,
>>  };
>>  
>> +static const struct arm64_ftr_bits ftr_id_mmfr5[] = {
>> +	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_MMFR5_ETS_SHIFT, 4, 0),
>> +	ARM64_FTR_END,
>> +};
>> +
>>  static const struct arm64_ftr_bits ftr_id_isar6[] = {
>>  	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR6_I8MM_SHIFT, 4, 0),
>>  	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_ISAR6_BF16_SHIFT, 4, 0),
>> @@ -527,6 +532,7 @@ static const struct __ftr_reg_entry {
>>  	ARM64_FTR_REG(SYS_MVFR2_EL1, ftr_mvfr2),
>>  	ARM64_FTR_REG(SYS_ID_PFR2_EL1, ftr_id_pfr2),
>>  	ARM64_FTR_REG(SYS_ID_DFR1_EL1, ftr_id_dfr1),
>> +	ARM64_FTR_REG(SYS_ID_MMFR5_EL1, ftr_id_mmfr5),
>>  
>>  	/* Op1 = 0, CRn = 0, CRm = 4 */
>>  	ARM64_FTR_REG(SYS_ID_AA64PFR0_EL1, ftr_id_aa64pfr0),
>> @@ -732,6 +738,7 @@ void __init init_cpu_features(struct cpuinfo_arm64 *info)
>>  		init_cpu_ftr_reg(SYS_ID_MMFR1_EL1, info->reg_id_mmfr1);
>>  		init_cpu_ftr_reg(SYS_ID_MMFR2_EL1, info->reg_id_mmfr2);
>>  		init_cpu_ftr_reg(SYS_ID_MMFR3_EL1, info->reg_id_mmfr3);
>> +		init_cpu_ftr_reg(SYS_ID_MMFR5_EL1, info->reg_id_mmfr5);
>>  		init_cpu_ftr_reg(SYS_ID_PFR0_EL1, info->reg_id_pfr0);
>>  		init_cpu_ftr_reg(SYS_ID_PFR1_EL1, info->reg_id_pfr1);
>>  		init_cpu_ftr_reg(SYS_ID_PFR2_EL1, info->reg_id_pfr2);
>> @@ -866,6 +873,8 @@ static int update_32bit_cpu_features(int cpu, struct cpuinfo_arm64 *info,
>>  				      info->reg_id_mmfr2, boot->reg_id_mmfr2);
>>  	taint |= check_update_ftr_reg(SYS_ID_MMFR3_EL1, cpu,
>>  				      info->reg_id_mmfr3, boot->reg_id_mmfr3);
> 
> Looks like MMFR4 is missing here?

ID_MMFR4 is missing from cpuinfo_arm64 itself, hence from init_cpu_features()
and update_cpu_features() as well. But it is defined in arm64_ftr_regs[]. I
was wondering about it but left as it is (due to lack of complete context).
Unless there is any other concern, will add it up in cpuinfo_arm64 and make
it a part of the CPU context.