[PATCH 02/17] arm64: Add KVM_HVHE capability and has_hvhe() predicate

[Oliver Upton]

On Thu, Oct 20, 2022 at 10:07:12AM +0100, Marc Zyngier wrote:
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index a3959e9f7d55..efac89c4c548 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1932,6 +1932,15 @@ static void cpu_copy_el2regs(const struct arm64_cpu_capabilities *__unused)
>  		write_sysreg(read_sysreg(tpidr_el1), tpidr_el2);
>  }
>  
> +static bool hvhe_possible(const struct arm64_cpu_capabilities *entry,
> +			  int __unused)
> +{
> +	u64 val;
> +
> +	val = arm64_sw_feature_override.val & arm64_sw_feature_override.mask;
> +	return cpuid_feature_extract_unsigned_field(val, ARM64_SW_FEATURE_OVERRIDE_HVHE);
> +}

Does this need to test ID_AA64MMFR1_EL1.VH as well? Otherwise I don't
see what would stop us from attempting hVHE on a system with asymmetric
support for VHE, as the software override was only evaluated on the boot
CPU.

> +
>  #ifdef CONFIG_ARM64_PAN
>  static void cpu_enable_pan(const struct arm64_cpu_capabilities *__unused)
>  {
> @@ -2642,6 +2651,12 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
>  		.matches = has_cpuid_feature,
>  		.cpu_enable = cpu_trap_el0_impdef,
>  	},
> +	{
> +		.desc = "VHE for hypervisor only",
> +		.capability = ARM64_KVM_HVHE,
> +		.type = ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE,
> +		.matches = hvhe_possible,
> +	},
>  	{},
>  };
>  
> diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
> index f1c0347ec31a..cee2be85b89b 100644
> --- a/arch/arm64/tools/cpucaps
> +++ b/arch/arm64/tools/cpucaps
> @@ -43,6 +43,7 @@ HAS_TLB_RANGE
>  HAS_VIRT_HOST_EXTN
>  HAS_WFXT
>  HW_DBM
> +KVM_HVHE
>  KVM_PROTECTED_MODE
>  MISMATCHED_CACHE_TYPE
>  MTE
> -- 
> 2.34.1
> 

-- 
Thanks,
Oliver