linux-kernel - Re: [PATCH v2 05/17] arm64: Helper for parange to PASize

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Date:   Fri, 27 Apr 2018 16:18:06 +0100
From:   Suzuki K Poulose <Suzuki.Poulose@....com>
To:     Julien Grall <julien.grall@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     ard.biesheuvel@...aro.org, kvm@...r.kernel.org,
        marc.zyngier@....com, catalin.marinas@....com,
        punit.agrawal@....com, will.deacon@....com,
        linux-kernel@...r.kernel.org, kristina.martsenko@....com,
        pbonzini@...hat.com, kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCH v2 05/17] arm64: Helper for parange to PASize

On 26/04/18 11:58, Julien Grall wrote:
> Hi Suzuki,
> 
> On 27/03/18 14:15, Suzuki K Poulose wrote:
>> Add a helper to convert ID_AA64MMFR0_EL1:PARange to they physical
>> size shift. Limit the size to the maximum supported by the kernel.
>> We are about to move the user of this code and this helps to
>> keep the changes cleaner.
> 
> It is probably worth to mention that you are also adding 52-bit support in the patch.

Sure, will do. Can I take that as a Reviewed-by with the fixed
commit description ?

Cheers
Suzuki

> 
> Cheers,
> 
>>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will.deacon@....com>
>> Cc: Marc Zyngier <marc.zyngier@....com>
>> Cc: Christoffer Dall <cdall@...nel.org>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
>> ---
>>   arch/arm64/include/asm/cpufeature.h | 16 ++++++++++++++++
>>   arch/arm64/kvm/hyp/s2-setup.c       | 28 +++++-----------------------
>>   2 files changed, 21 insertions(+), 23 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
>> index fbf0aab..1f2a5dd 100644
>> --- a/arch/arm64/include/asm/cpufeature.h
>> +++ b/arch/arm64/include/asm/cpufeature.h
>> @@ -311,6 +311,22 @@ static inline u64 read_zcr_features(void)
>>       return zcr;
>>   }
>> +static inline u32 id_aa64mmfr0_parange_to_phys_shift(int parange)
>> +{
>> +    switch (parange) {
>> +    case 0: return 32;
>> +    case 1: return 36;
>> +    case 2: return 40;
>> +    case 3: return 42;
>> +    case 4: return 44;
>> +    /* Report 48 bit if the kernel doesn't support 52bit */
>> +    default:
>> +    case 5: return 48;
>> +#ifdef CONFIG_ARM64_PA_BITS_52
>> +    case 6: return 52;
>> +#endif
>> +    }
>> +}
>>   #endif /* __ASSEMBLY__ */
>>   #endif
>> diff --git a/arch/arm64/kvm/hyp/s2-setup.c b/arch/arm64/kvm/hyp/s2-setup.c
>> index 603e1ee..b1129c8 100644
>> --- a/arch/arm64/kvm/hyp/s2-setup.c
>> +++ b/arch/arm64/kvm/hyp/s2-setup.c
>> @@ -19,11 +19,13 @@
>>   #include <asm/kvm_arm.h>
>>   #include <asm/kvm_asm.h>
>>   #include <asm/kvm_hyp.h>
>> +#include <asm/cpufeature.h>
>>   u32 __hyp_text __init_stage2_translation(void)
>>   {
>>       u64 val = VTCR_EL2_FLAGS;
>>       u64 parange;
>> +    u32 phys_shift;
>>       u64 tmp;
>>       /*
>> @@ -37,27 +39,7 @@ u32 __hyp_text __init_stage2_translation(void)
>>       val |= parange << 16;
>>       /* Compute the actual PARange... */
>> -    switch (parange) {
>> -    case 0:
>> -        parange = 32;
>> -        break;
>> -    case 1:
>> -        parange = 36;
>> -        break;
>> -    case 2:
>> -        parange = 40;
>> -        break;
>> -    case 3:
>> -        parange = 42;
>> -        break;
>> -    case 4:
>> -        parange = 44;
>> -        break;
>> -    case 5:
>> -    default:
>> -        parange = 48;
>> -        break;
>> -    }
>> +    phys_shift = id_aa64mmfr0_parange_to_phys_shift(parange);
>>       /*
>>        * ... and clamp it to 40 bits, unless we have some braindead
>> @@ -65,7 +47,7 @@ u32 __hyp_text __init_stage2_translation(void)
>>        * return that value for the rest of the kernel to decide what
>>        * to do.
>>        */
>> -    val |= 64 - (parange > 40 ? 40 : parange);
>> +    val |= 64 - (phys_shift > 40 ? 40 : phys_shift);
>>       /*
>>        * Check the availability of Hardware Access Flag / Dirty Bit
>> @@ -86,5 +68,5 @@ u32 __hyp_text __init_stage2_translation(void)
>>       write_sysreg(val, vtcr_el2);
>> -    return parange;
>> +    return phys_shift;
>>   }
>>
>