linux-kernel - Re: [PATCH v15 5/6] KVM: arm64: Allow GCS to be enabled for guests

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Message-ID: <87jz2xk57m.wl-maz@kernel.org>
Date: Wed, 20 Aug 2025 23:18:05 +0100
From: Marc Zyngier <maz@...nel.org>
To: Mark Brown <broonie@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Shuah Khan <shuah@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-doc@...r.kernel.org,
	kvmarm@...ts.linux.dev,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v15 5/6] KVM: arm64: Allow GCS to be enabled for guests

On Wed, 20 Aug 2025 15:14:45 +0100,
Mark Brown <broonie@...nel.org> wrote:
> 
> Now that required functionality for GCS is in place expose
> ID_AA64PFR1_EL1.GCS, allowing guests to be given the feature.
> 
> Signed-off-by: Mark Brown <broonie@...nel.org>
> ---
>  arch/arm64/kvm/sys_regs.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 592cb5d6497a..60e234422064 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1616,7 +1616,6 @@ static u64 __kvm_read_sanitised_id_reg(const struct kvm_vcpu *vcpu,
>  		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_SME);
>  		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_RNDR_trap);
>  		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_NMI);
> -		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_GCS);
>  		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_THE);
>  		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_MTEX);
>  		val &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_EL1_PFAR);
> 

Still disabled for NV in limit_nv_id_reg().

	M.

-- 
Jazz isn't dead. It just smells funny.