Subject: Re: [PATCH v7 6/7] KVM: arm64: Enable FEAT_{LS64, LS64_V} in the supported guest

From: Oliver Upton <[email-masked]>
Date: Fri, 7 Nov 2025 10:53:50 -0800

Hi Zhou,

On Fri, Nov 07, 2025 at 03:21:26PM +0800, Zhou Wang wrote:
> From: Yicong Yang <[email-masked]>
> 
> Using FEAT_{LS64, LS64_V} instructions in a guest is also controlled
> by HCRX_EL2.{EnALS, EnASR}. Enable it if guest has related feature.
> 
> Signed-off-by: Yicong Yang <[email-masked]>
> Signed-off-by: Zhou Wang <[email-masked]>

The ordering of this patch is incorrect as patch #5 has the side-effect
of exposing ID_AA64ISAR1_EL1.LS64 to KVM guests. This one should come
first instead.

Thanks,
Oliver

> ---
>  arch/arm64/include/asm/kvm_emulate.h | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index bab967d65715..29291e25ecfd 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -695,6 +695,12 @@ static inline void vcpu_set_hcrx(struct kvm_vcpu *vcpu)
>  
>  		if (kvm_has_sctlr2(kvm))
>  			vcpu->arch.hcrx_el2 |= HCRX_EL2_SCTLR2En;
> +
> +		if (kvm_has_feat(kvm, ID_AA64ISAR1_EL1, LS64, LS64))
> +			vcpu->arch.hcrx_el2 |= HCRX_EL2_EnALS;
> +
> +		if (kvm_has_feat(kvm, ID_AA64ISAR1_EL1, LS64, LS64_V))
> +			vcpu->arch.hcrx_el2 |= HCRX_EL2_EnASR;
>  	}
>  }
>  #endif /* __ARM64_KVM_EMULATE_H__ */
> -- 
> 2.33.0
> 
>