[PATCH v3 11/28] KVM: arm64: Expose FEAT_NV2p1 to NV guests

[Yao Yuan]

On Wed, Jul 22, 2026 at 08:42:17AM +0800, Marc Zyngier wrote:
> Since NV2p1 is reducing the number of traps, it is valuable to expose
> it to NV guests. Do so.

Reviewed-by: Yuan Yao <yaoyuan at linux.alibaba.com>

>
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/kvm/nested.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
> index dfb96edbdc43c..35a1c42ad3f84 100644
> --- a/arch/arm64/kvm/nested.c
> +++ b/arch/arm64/kvm/nested.c
> @@ -1728,7 +1728,7 @@ u64 limit_nv_id_reg(struct kvm *kvm, u32 reg, u64 val)
>  		 * You get EITHER
>  		 *
>  		 * - FEAT_VHE without FEAT_E2H0
> -		 * - FEAT_NV limited to FEAT_NV2
> +		 * - FEAT_NV limited to FEAT_NV2(p1)
>  		 * - HCR_EL2.NV1 being RES0
>  		 *
>  		 * OR
> @@ -1740,7 +1740,11 @@ u64 limit_nv_id_reg(struct kvm *kvm, u32 reg, u64 val)
>  		if (test_bit(KVM_ARM_VCPU_HAS_EL2_E2H0, kvm->arch.vcpu_features)) {
>  			val = 0;
>  		} else {
> -			val = SYS_FIELD_PREP_ENUM(ID_AA64MMFR4_EL1, NV_frac, NV2_ONLY);
> +			val &= ID_AA64MMFR4_EL1_NV_frac;
> +			if (cpus_have_final_cap(ARM64_HAS_NV2P1))
> +				val = ID_REG_LIMIT_FIELD_ENUM(val, ID_AA64MMFR4_EL1, NV_frac, NV2P1);
> +			else
> +				val = SYS_FIELD_PREP_ENUM(ID_AA64MMFR4_EL1, NV_frac, NV2_ONLY);
>  			val |= SYS_FIELD_PREP_ENUM(ID_AA64MMFR4_EL1, E2H0, NI_NV1);
>  		}
>  		break;
> --
> 2.47.3