linux-kernel - Re: [PATCH v3 03/20] arm64: Add a helper for PARange to physical shift conversion

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Date:   Fri, 29 Jun 2018 16:50:35 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     cdall@...nel.org, kvm@...r.kernel.org, marc.zyngier@....com,
        catalin.marinas@....com, punit.agrawal@....com,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        qemu-devel@...gnu.org, julien.grall@....com, james.morse@....com,
        kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCH v3 03/20] arm64: Add a helper for PARange to physical
 shift conversion

Hi Suzuki,

On 06/29/2018 01:15 PM, Suzuki K Poulose wrote:
> On arm64, ID_AA64MMFR0_EL1.PARange encodes the maximum Physical
> Address range supported by the CPU. Add a helper to decode this
> to actual physical shift. If we hit an unallocated value, return
> the maximum range supported by the kernel.
> This is will be used by the KVM to set the VTCR_EL2.T0SZ, as it
s/is// and s/the KVM/KVM
> is about to move its place. Having this helper keeps the code
> movement cleaner.
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: James Morse <james.morse@....com>
> Cc: Christoffer Dall <cdall@...nel.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
> Changes since V2:
>  - Split the patch
>  - Limit the physical shift only for values unrecognized.
> ---
>  arch/arm64/include/asm/cpufeature.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index 1717ba1..855cf0e 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -530,6 +530,19 @@ void arm64_set_ssbd_mitigation(bool state);
>  static inline void arm64_set_ssbd_mitigation(bool state) {}
>  #endif
>  
> +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;
> +	case 5: return 48;
> +	case 6: return 52;
> +	default: return CONFIG_ARM64_PA_BITS;
> +	}
> +}
>  #endif /* __ASSEMBLY__ */
>  
>  #endif
>

Reviewed-by: Eric Auger <eric.auger@...hat.com>

Thanks

Eric