[PATCH 02/16] arm64: Add HAS_ECV_CNTPOFF capability

[Reiji Watanabe]

Hi Marc,

On Thu, Feb 16, 2023 at 6:21 AM Marc Zyngier <maz at kernel.org> wrote:
>
> Add the probing code for the FEAT_ECV variant that implements CNTPOFF_EL2.
> Why is it optional is a mystery, but let's try and detect it.
>
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/kernel/cpufeature.c | 11 +++++++++++
>  arch/arm64/tools/cpucaps       |  1 +
>  2 files changed, 12 insertions(+)
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 23bd2a926b74..36852f96898d 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -2186,6 +2186,17 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
>                 .sign = FTR_UNSIGNED,
>                 .min_field_value = 1,
>         },
> +       {
> +               .desc = "Enhanced Counter Virtualization (CNTPOFF)",
> +               .capability = ARM64_HAS_ECV_CNTPOFF,
> +               .type = ARM64_CPUCAP_SYSTEM_FEATURE,
> +               .matches = has_cpuid_feature,
> +               .sys_reg = SYS_ID_AA64MMFR0_EL1,
> +               .field_pos = ID_AA64MMFR0_EL1_ECV_SHIFT,
> +               .field_width = 4,
> +               .sign = FTR_UNSIGNED,
> +               .min_field_value = 2,

Nit: You might want to use ID_AA64MMFR0_EL1_ECV_CNTPOFF (instead of 2) ?

Reviewed-by: Reiji Watanabe <reijiw at google.com>

Thank you,
Reiji

> +       },
>  #ifdef CONFIG_ARM64_PAN
>         {
>                 .desc = "Privileged Access Never",
> diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
> index 82c7e579a8ba..6a26a4678406 100644
> --- a/arch/arm64/tools/cpucaps
> +++ b/arch/arm64/tools/cpucaps
> @@ -23,6 +23,7 @@ HAS_DCPOP
>  HAS_DIT
>  HAS_E0PD
>  HAS_ECV
> +HAS_ECV_CNTPOFF
>  HAS_EPAN
>  HAS_GENERIC_AUTH
>  HAS_GENERIC_AUTH_ARCH_QARMA3
> --
> 2.34.1
>
>