Re: [PATCH v3 27/28] KVM: arm64: Expose FEAT_NV3 to guests

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The new system register NVHCR_EL2, which is exposed to userspace when FEAT_NV3 is enabled, is not registered in the get-reg-list selftest.
--

--- Patch [27]: [PATCH v3 27/28] KVM: arm64: Expose FEAT_NV3 to guests ---
commit 736b25683999a8114fb8bc21450f4b90835ba889
Author: Marc Zyngier <maz@kernel.org>

KVM: arm64: Expose FEAT_NV3 to guests

This commit further enables FEAT_NV3 by making it visible to NV guests.

> diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
> --- a/arch/arm64/kvm/nested.c
> +++ b/arch/arm64/kvm/nested.c
> @@ -1739,7 +1739,9 @@ u64 limit_nv_id_reg(struct kvm *kvm, u32 reg, u64 val)
>  			val = 0;
>  		} else {
>  			val &= ID_AA64MMFR4_EL1_NV_frac;
> -			if (cpus_have_final_cap(ARM64_HAS_NV2P1))
> +			if (cpus_have_final_cap(ARM64_HAS_NV3))
> +				val = ID_REG_LIMIT_FIELD_ENUM(val, ID_AA64MMFR4_EL1, NV_frac, NV3);

[Severity: Medium]
By exposing FEAT_NV3 here, will new system registers like NVHCR_EL2 become
visible to userspace on NV3-capable hardware? If so, does the get-reg-list
selftest in tools/testing/selftests/kvm/arm64/get-reg-list.c need to be
updated (e.g., adding them to el2_regs or using REG_FEAT) to prevent the
test suite from failing when it discovers unaccounted registers?

> +			else 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);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260722074234.3330999-1-maz@kernel.org?part=27