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

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Message-ID: <aab025fd-a9aa-0f1a-783b-eb5d3b40a327@arm.com>
Date:   Tue, 19 May 2020 14:32:10 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     anshuman.khandual@....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 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.

>   	S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_TGRAN4_SHIFT, 4, ID_AA64MMFR0_TGRAN4_NI),
>   	S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_TGRAN64_SHIFT, 4, ID_AA64MMFR0_TGRAN64_NI),
>   	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_TGRAN16_SHIFT, 4, ID_AA64MMFR0_TGRAN16_NI),
> 

Suzuki