linux-kernel - Re: [PATCH 6/6] arm64/cpufeature: Replace all open bits shift encodings with macros

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Date:   Thu, 2 Apr 2020 08:14:32 +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, james.morse@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] arm64/cpufeature: Replace all open bits shift
 encodings with macros



On 03/21/2020 12:10 AM, Suzuki K Poulose wrote:
> On 01/28/2020 12:39 PM, Anshuman Khandual wrote:
>> There are many open bits shift encodings for various CPU ID registers that
>> are scattered across cpufeature. This replaces them with register specific
>> sensible macro definitions. This should not have any functional change.
>>
>> 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: linux-kernel@...r.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
> 
> 
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -263,7 +263,7 @@ static const struct arm64_ftr_bits ftr_ctr[] = {
>>        * make use of *minLine.
>>        * If we have differing I-cache policies, report it as the weakest - VIPT.
>>        */
>> -    ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_EXACT, 14, 2, ICACHE_POLICY_VIPT),    /* L1Ip */
>> +    ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_EXACT, CTR_L1IP_SHIFT, 2, ICACHE_POLICY_VIPT),    /* L1Ip */
>>       ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, CTR_IMINLINE_SHIFT, 4, 0),
>>       ARM64_FTR_END,
>>   };
>> @@ -274,19 +274,19 @@ struct arm64_ftr_reg arm64_ftr_reg_ctrel0 = {
>>   };
>>     static const struct arm64_ftr_bits ftr_it will not be a good idea to id_mmfr0[] = {
>> -    S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 28, 4, 0xf),    /* InnerShr */
>> -    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 24, 4, 0),    /* FCSE */
>> -    ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, 20, 4, 0),    /* AuxReg */
>> -    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 16, 4, 0),    /* TCM */
>> -    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 12, 4, 0),    /* ShareLvl */
>> -    S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 8, 4, 0xf),    /* OuterShr */
>> -    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 4, 4, 0),    /* PMSA */
>> -    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 0, 4, 0),    /* VMSA */
>> +    S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_MMFR0_INNERSHR_SHIFT, 4, 0xf),
>> +    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_MMFR0_FCSE_SHIFT, 4, 0),
>> +    ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_MMFR0_AUXREG_SHIFT, 4, 0),
>> +    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_MMFR0_TCM_SHIFT, 4, 0),
>> +    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_MMFR0_SHARELVL_SHIFT, 4, 0),
>> +    S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_MMFR0_OUTERSHR_SHIFT, 4, 0xf),
>> +    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_MMFR0_PMSA_SHIFT, 4, 0),
>> +    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_MMFR0_VMSA_SHIFT, 4, 0),
>>       ARM64_FTR_END,
>>   };
>>     static const struct arm64_ftr_bits ftr_id_aa64dfr0[] = {
>> -    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, 36, 28, 0),
>> +    ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, ID_AA64DFR0_DOUBLELOCK_SHIFT, 28, 0),
> 
> This must be a signed feature, as we have the following possible values :
> 
>     0b0000 - Double lock implemented
>     0b1111 - Double lock not implemented.
> 
> So, in case of a conflict we want the safe value as 0b1111.
> 
> Please could you fix this as well ?

Sure but in a separate patch, as would like to prevent mixing any
actual code change from macro replacement.

> 
> 
> This patch as such looks fine to me.
> 
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
>