linux-kernel - Re: [PATCH v3 14/17] arm64: Add a capability for FEAT

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Date:   Mon, 11 Oct 2021 11:56:30 +0100
From:   Will Deacon <will@...nel.org>
To:     Marc Zyngier <maz@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Shier <pshier@...gle.com>,
        Raghavendra Rao Ananta <rananta@...gle.com>,
        Ricardo Koller <ricarkol@...gle.com>,
        Oliver Upton <oupton@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Linus Walleij <linus.walleij@...aro.org>,
        kernel-team@...roid.com
Subject: Re: [PATCH v3 14/17] arm64: Add a capability for FEAT_ECV

On Sun, Oct 10, 2021 at 12:43:03PM +0100, Marc Zyngier wrote:
> Add a new capability to detect the Enhanced Counter Virtualization
> feature (FEAT_ECV).
> 
> Reviewed-by: Oliver Upton <oupton@...gle.com>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>  arch/arm64/kernel/cpufeature.c | 10 ++++++++++
>  arch/arm64/tools/cpucaps       |  1 +
>  2 files changed, 11 insertions(+)
> 
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index f8a3067d10c6..26b11ce8fff6 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1926,6 +1926,16 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
>  		.sign = FTR_UNSIGNED,
>  		.min_field_value = 1,
>  	},
> +	{
> +		.desc = "Enhanced Counter Virtualization",
> +		.capability = ARM64_HAS_ECV,
> +		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
> +		.matches = has_cpuid_feature,
> +		.sys_reg = SYS_ID_AA64MMFR0_EL1,
> +		.field_pos = ID_AA64MMFR0_ECV_SHIFT,
> +		.sign = FTR_UNSIGNED,
> +		.min_field_value = 1,
> +	},
>  #ifdef CONFIG_ARM64_PAN
>  	{
>  		.desc = "Privileged Access Never",
> diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
> index 49305c2e6dfd..7a7c58acd8f0 100644
> --- a/arch/arm64/tools/cpucaps
> +++ b/arch/arm64/tools/cpucaps
> @@ -18,6 +18,7 @@ HAS_CRC32
>  HAS_DCPODP
>  HAS_DCPOP
>  HAS_E0PD
> +HAS_ECV
>  HAS_EPAN
>  HAS_GENERIC_AUTH
>  HAS_GENERIC_AUTH_ARCH

We should also make the ECV field FTR_VISIBLE.

Will