linux-kernel - Re: [PATCH 16/24] arm64: cpucaps: Add GCIE capability

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Message-ID: <Z_UH0808dGkS3v7-@J2N7QTR9R3.cambridge.arm.com>
Date: Tue, 8 Apr 2025 12:26:11 +0100
From: Mark Rutland <mark.rutland@....com>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>
Cc: Marc Zyngier <maz@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Sascha Bischoff <sascha.bischoff@....com>,
	Timothy Hayes <timothy.hayes@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH 16/24] arm64: cpucaps: Add GCIE capability

On Tue, Apr 08, 2025 at 12:50:15PM +0200, Lorenzo Pieralisi wrote:
> Implement the GCIE capability as a strict boot cpu capability to
> detect whether architectural GICv5 support is available in HW.
> 
> Signed-off-by: Lorenzo Pieralisi <lpieralisi@...nel.org>
> Cc: Will Deacon <will@...nel.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Marc Zyngier <maz@...nel.org>

This looks good; I have a minor consistency/bikeshedding concern below.

> ---
>  arch/arm64/kernel/cpufeature.c | 7 +++++++
>  arch/arm64/tools/cpucaps       | 1 +
>  2 files changed, 8 insertions(+)
> 
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 9c4d6d552b25cb3a31d1fb267bd73d3f82513e69..8c60591633f3d435ad9b80a10e484f26af328964 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -3041,6 +3041,13 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
>  		.matches = has_pmuv3,
>  	},
>  #endif
> +	{
> +		.desc = "GCIE",
> +		.type = ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE,
> +		.capability = ARM64_HAS_GCIE,
> +		.matches = has_cpuid_feature,
> +		ARM64_CPUID_FIELDS(ID_AA64PFR2_EL1, GCIE, IMP)
> +	},

I reckon it's worth making the desc a bit clearer, e.g. "GICv5 CPU
interface".

It might be worth cleaning up the existing ARM64_HAS_GIC_CPUIF_SYSREGS
feature, e.g. making that have "GICv3 CPU interface" as its desc.

Likewise, could make the names consistent, e.g. have:

	ARM64_HAS_GICV3_CPUIF
	ARM64_HAS_GICV5_CPUIF

... ?

Mark.