linux-kernel - Re: [PATCH V4 15/17] arm64/cpufeature: Add remaining feature bits in ID

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Message-ID: <9e452a85-2ccf-50e6-d807-3f9e528b4072@arm.com>
Date:   Sun, 24 May 2020 06:38:42 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     catalin.marinas@....com, will@...nel.org, maz@...nel.org,
        mark.rutland@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 15/17] arm64/cpufeature: Add remaining feature bits in
 ID_AA64DFR0 register



On 05/20/2020 07:27 PM, Suzuki K Poulose wrote:
> On 05/19/2020 10:40 AM, Anshuman Khandual wrote:
>> Enable MTPMU and TRACEFILT features bits in ID_AA64DFR0 register as per ARM
>> DDI 0487F.a specification.
>>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: Suzuki K Poulose <suzuki.poulose@....com>
>> 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/sysreg.h | 2 ++
>>   arch/arm64/kernel/cpufeature.c  | 2 ++
>>   2 files changed, 4 insertions(+)
>>
>> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
>> index a572069ccf6e..4bcd21cc2d68 100644
>> --- a/arch/arm64/include/asm/sysreg.h
>> +++ b/arch/arm64/include/asm/sysreg.h
>> @@ -766,6 +766,8 @@
>>   #define ID_AA64MMFR2_CNP_SHIFT        0
>>     /* id_aa64dfr0 */
>> +#define ID_AA64DFR0_MTPMU_SHIFT        48
>> +#define ID_AA64DFR0_TRACEFILT_SHIFT    40
>>   #define ID_AA64DFR0_PMSVER_SHIFT    32
>>   #define ID_AA64DFR0_CTX_CMPS_SHIFT    28
>>   #define ID_AA64DFR0_WRPS_SHIFT        20
>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>> index 6338151f263c..986974be0178 100644
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -366,6 +366,8 @@ static const struct arm64_ftr_bits ftr_id_mmfr0[] = {
>>   };
>>     static const struct arm64_ftr_bits ftr_id_aa64dfr0[] = {
>> +    S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64DFR0_MTPMU_SHIFT, 4, 0),
>> +    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64DFR0_TRACEFILT_SHIFT, 4, 0),
> 
> We maske both the fields for KVM in AArch32 ID registers. We should do the same here.

MTPMU is defined for AArch32 ID register ID_DFR1_EL1, even though the
entire register is hidden from KVM with ID_HIDDEN().

static const struct arm64_ftr_bits ftr_id_dfr1[] = {
        S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_DFR1_MTPMU_SHIFT, 4, 0),
        ARM64_FTR_END,
};

Should the ID_AA64DFR0_EL1 be hidden from KVM as well. But it has many
other existing features apart from MTPMU and TRACEFILT which are being
added here.