Re: [PATCH v22 09/23] KVM: arm64: Prevent unsupported vcpu features for VM types

[Gavin Shan]

On 10/5/26 7:07 PM, Suzuki K Poulose wrote:
> Prevent unsupported VCPU features for the protected VCPUs. Realms and pVMs
> not support 32bit EL1 or NV yet. pKVM doesn't rely on the host vcpu
> features and it clears the unsupported features while hyp_vcpu is
> initialised. Block the features early in the vcpu init if we detect
> incompatible features.
>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
>   arch/arm64/kvm/arm.c | 10 ++++++----
>   1 file changed, 6 insertions(+), 4 deletions(-)

One nitpick below. In either way:

Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>

> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index f31d31fa27ad9..9c2ef7ca6a961 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1668,11 +1668,12 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level,
>   	return -EINVAL;
>   }
>   
> -static unsigned long system_supported_vcpu_features(void)
> +static unsigned long system_supported_vcpu_features(struct kvm_vcpu *vcpu)
>   {
>   	unsigned long features = KVM_VCPU_VALID_FEATURES;
>   
> -	if (!cpus_have_final_cap(ARM64_HAS_32BIT_EL1))
> +	if (vcpu_is_protected(vcpu) ||
> +	    !cpus_have_final_cap(ARM64_HAS_32BIT_EL1))
>   		clear_bit(KVM_ARM_VCPU_EL1_32BIT, &features);
>   
>   	if (!kvm_supports_guest_pmuv3()) {
> @@ -1688,7 +1689,8 @@ static unsigned long system_supported_vcpu_features(void)
>   		clear_bit(KVM_ARM_VCPU_PTRAUTH_GENERIC, &features);
>   	}
>   
> -	if (!cpus_have_final_cap(ARM64_HAS_NESTED_VIRT))
> +	if (vcpu_is_protected(vcpu) ||
> +	    !cpus_have_final_cap(ARM64_HAS_NESTED_VIRT))
>   		clear_bit(KVM_ARM_VCPU_HAS_EL2, &features);
>   
>   	return features;
> @@ -1708,7 +1710,7 @@ static int kvm_vcpu_init_check_features(struct kvm_vcpu *vcpu,
>   			return -ENOENT;
>   	}
>   
> -	if (features & ~system_supported_vcpu_features())
> +	if (features & ~system_supported_vcpu_features(vcpu))
>   		return -EINVAL;
>  

The following check at the beginning of kvm_vcpu_init_check_features() is redundant to
the check here. We can drop that in this patch or a preparatory patch.

static int kvm_vcpu_init_check_features(...)
{
       /*
        * This check can be dropped since the same check has been done
	* by the followup "if (features & ~system_supported_vcpu_features(vcpu))"
        */
       if (features & ~KVM_VCPU_VALID_FEATURES)
                return -ENOENT;
}

 
>   	/*

Thanks,
Gavin