linux-kernel - Re: [PATCH V4 12/17] arm64/cpufeature: Add remaining feature bits in ID

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Message-ID: <4df6059d-baad-0f21-ec0d-cbb972bfabdf@arm.com>
Date:   Mon, 25 May 2020 04:38:13 +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 12/17] arm64/cpufeature: Add remaining feature bits in
 ID_AA64MMFR0 register



On 05/19/2020 07:02 PM, Suzuki K Poulose wrote:
> On 05/19/2020 10:40 AM, Anshuman Khandual wrote:
>> Enable EVC, FGT, EXS, TGRAN4_2, TGRAN64_2 and TGRAN16_2 features bits in
>> ID_AA64MMFR0 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>
> 
>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>> index d1433f996710..7ce19f97ba73 100644
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -267,6 +267,10 @@ static const struct arm64_ftr_bits ftr_id_aa64zfr0[] = {
>>   };
>>     static const struct arm64_ftr_bits ftr_id_aa64mmfr0[] = {
>> +
> 
> minor nit: spurious new line.
> 
>> +    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_ECV_SHIFT, 4, 0),
>> +    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_FGT_SHIFT, 4, 0),
>> +    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_EXS_SHIFT, 4, 0),
>>       /*
>>        * We already refuse to boot CPUs that don't support our configured
>>        * page size, so we can only detect mismatches for a page size other
>> @@ -274,6 +278,9 @@ static const struct arm64_ftr_bits ftr_id_aa64mmfr0[] = {
>>        * exist in the wild so, even though we don't like it, we'll have to go
>>        * along with it and treat them as non-strict.
>>        */
>> +    S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_TGRAN4_2_SHIFT, 4, ID_AA64MMFR0_TGRAN4_2_NI),
>> +    S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_TGRAN64_2_SHIFT, 4, ID_AA64MMFR0_TGRAN64_2_NI),
>> +    S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_TGRAN16_2_SHIFT, 4, ID_AA64MMFR0_TGRAN16_2_NI),
> 
> These are not SIGNED as they don't have 0b1111 defined to represent
> something "lower" than '0b0'. It was signed for 4K and 64K, since
> 
> 0b0000 => supported
> 0b1111 => Not supported.
> 
> Also Please note, KVM-NV patches are adding these, so you may as well drop them.

Sure, will drop all ID_AA64MMFR0_TGRAN changes along with related
macros from arch/arm64/include/asm/sysreg.h.