Re: [PATCH v4 06/20] arm64: Add a helper for PARange to physical shift conversion

Christoffer Dall
2018-08-30T09:42:31Z

On Wed, Jul 18, 2018 at 10:18:49AM +0100, 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 will be used by KVM to set the VTCR_EL2.T0SZ, as it
> is about to move its place. Having this helper keeps the code
> movement cleaner.
>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Cc: James Morse <james.morse@arm.com>
> Cc: Christoffer Dall <cdall@kernel.org>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.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;

I don't understand this case? Shouldn't this include at least a WARN()
?

Thanks,
Christoffer

> + }
> +}
> #endif /* __ASSEMBLY__ */
>
> #endif
> --
> 2.7.4
>
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