Re: [PATCH v6 28/43] arm64: rme: Allow checking SVE on VM instance

[Gavin Shan <gshan@redhat.com>]

On 12/13/24 1:55 AM, Steven Price wrote:
> From: Suzuki K Poulose <suzuki.poulose@arm.com>
> 
> Given we have different types of VMs supported, check the
> support for SVE for the given instance of the VM to accurately
> report the status.
> 
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>   arch/arm64/include/asm/kvm_rme.h | 2 ++
>   arch/arm64/kvm/arm.c             | 5 ++++-
>   arch/arm64/kvm/rme.c             | 5 +++++
>   3 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/asm/kvm_rme.h
> index 90a4537ad38d..0d89ab1645c1 100644
> --- a/arch/arm64/include/asm/kvm_rme.h
> +++ b/arch/arm64/include/asm/kvm_rme.h
> @@ -85,6 +85,8 @@ void kvm_init_rme(void);
>   u32 kvm_realm_ipa_limit(void);
>   u32 kvm_realm_vgic_nr_lr(void);
>   
> +bool kvm_rme_supports_sve(void);
> +
>   int kvm_realm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap);
>   int kvm_init_realm_vm(struct kvm *kvm);
>   void kvm_destroy_realm(struct kvm *kvm);
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 134acb4ee26f..6f7f96ab781d 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -456,7 +456,10 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>   		r = get_kvm_ipa_limit();
>   		break;
>   	case KVM_CAP_ARM_SVE:
> -		r = system_supports_sve();
> +		if (kvm_is_realm(kvm))
> +			r = kvm_rme_supports_sve();
> +		else
> +			r = system_supports_sve();
>   		break;

kvm_vm_ioctl_check_extension() can be called by ioctl(KVM_CHECK_EXTENSION) on the
file descriptor of '/dev/kvm'. kvm is NULL and kvm_is_realm() returns false in
this case.

kvm_dev_ioctl
   kvm_vm_ioctl_check_extension_generic  // kvm is NULL
     kvm_vm_ioctl_check_extension

>   	case KVM_CAP_ARM_PTRAUTH_ADDRESS:
>   	case KVM_CAP_ARM_PTRAUTH_GENERIC:
> diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
> index 5831d379760a..27a479feb907 100644
> --- a/arch/arm64/kvm/rme.c
> +++ b/arch/arm64/kvm/rme.c
> @@ -20,6 +20,11 @@ static bool rme_supports(unsigned long feature)
>   	return !!u64_get_bits(rmm_feat_reg0, feature);
>   }
>   
> +bool kvm_rme_supports_sve(void)
> +{
> +	return rme_supports(RMI_FEATURE_REGISTER_0_SVE_EN);
> +}
> +

If rme_supports() becomes a public helper, it can be directly used. In turn,
kvm_rme_supports_sve() can be dropped. RMI_FEATURE_REGISTER_0_SVE_EN is obvious
to indicate the corresponding feature.

>   static int rmi_check_version(void)
>   {
>   	struct arm_smccc_res res;

Thanks,
Gavin