Re: [PATCH v4 05/15] KVM: s390: enable/disable AP interpretive execution

[Pierre Morel]

On 15/04/2018 23:22, Tony Krowiak wrote:
> The VFIO AP device model exploits interpretive execution of AP
> instructions (APIE) to provide guests passthrough access to AP
> devices. This patch introduces a new interface to enable and
> disable APIE.
>
> Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx>
> ---
>   arch/s390/include/asm/kvm-ap.h   |   16 ++++++++++++++++
>   arch/s390/include/asm/kvm_host.h |    1 +
>   arch/s390/kvm/kvm-ap.c           |   20 ++++++++++++++++++++
>   arch/s390/kvm/kvm-s390.c         |    9 +++++++++
>   4 files changed, 46 insertions(+), 0 deletions(-)
>
> diff --git a/arch/s390/include/asm/kvm-ap.h b/arch/s390/include/asm/kvm-ap.h
> index 736e93e..a6c092e 100644
> --- a/arch/s390/include/asm/kvm-ap.h
> +++ b/arch/s390/include/asm/kvm-ap.h
> @@ -35,4 +35,20 @@
>    */
>   void kvm_ap_build_crycbd(struct kvm *kvm);
>
> +/**
> + * kvm_ap_interpret_instructions
> + *
> + * Indicate whether AP instructions shall be interpreted. If they are not
> + * interpreted, all AP instructions will be intercepted and routed back to
> + * userspace.
> + *
> + * @kvm: the virtual machine attributes
> + * @enable: indicates whether AP instructions are to be interpreted (true) or
> + *	    or not (false).
> + *
> + * Returns 0 if completed successfully; otherwise, returns -EOPNOTSUPP
> + * indicating that AP instructions are not installed on the guest.
> + */
> +int kvm_ap_interpret_instructions(struct kvm *kvm, bool enable);
> +
>   #endif /* _ASM_KVM_AP */
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 3162783..5470685 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -715,6 +715,7 @@ struct kvm_s390_crypto {
>   	__u32 crycbd;
>   	__u8 aes_kw;
>   	__u8 dea_kw;
> +	__u8 apie;
>   };
>
>   #define APCB0_MASK_SIZE 1
> diff --git a/arch/s390/kvm/kvm-ap.c b/arch/s390/kvm/kvm-ap.c
> index 991bae4..55d11b5 100644
> --- a/arch/s390/kvm/kvm-ap.c
> +++ b/arch/s390/kvm/kvm-ap.c
> @@ -58,3 +58,23 @@ void kvm_ap_build_crycbd(struct kvm *kvm)
>   	}
>   }
>   EXPORT_SYMBOL(kvm_ap_build_crycbd);
> +
> +int kvm_ap_interpret_instructions(struct kvm *kvm, bool enable)
> +{
> +	int ret = 0;
> +
> +	mutex_lock(&kvm->lock);
> +
> +	if (!test_kvm_cpu_feat(kvm, KVM_S390_VM_CPU_FEAT_AP)) {

Do we really need to test CPU_FEAT_AP?

I understand that KVM_S390_VM_CPU_FEAT_AP means AP instructions are 
interpreted.
shouldn't we add this information in the name?
like KVM_S390_VM_CPU_FEAT_APIE

> +		ret = -EOPNOTSUPP;
> +		goto done;
> +	}
> +
> +	kvm->arch.crypto.apie = enable;
> +	kvm_s390_vcpu_crypto_reset_all(kvm);
> +
> +done:
> +	mutex_unlock(&kvm->lock);
> +	return ret;
> +}
> +EXPORT_SYMBOL(kvm_ap_interpret_instructions);
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 55cd897..1dc8566 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -1901,6 +1901,9 @@ static void kvm_s390_crypto_init(struct kvm *kvm)
>   	kvm->arch.crypto.crycb = &kvm->arch.sie_page2->crycb;
>   	kvm_ap_build_crycbd(kvm);
>
> +	/* Default setting indicating SIE shall interpret AP instructions */
> +	kvm->arch.crypto.apie = 1;
> +
>   	if (!test_kvm_facility(kvm, 76))
>   		return;
>
> @@ -2434,6 +2437,12 @@ static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu)
>   {
>   	vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
>
> +	vcpu->arch.sie_block->eca &= ~ECA_APIE;
> +	if (vcpu->kvm->arch.crypto.apie &&
> +	    test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_AP))

Do we call xxx_crypto_setup() if KVM does not support AP interpretation?

> +		vcpu->arch.sie_block->eca |= ECA_APIE;
> +
> +
>   	if (!test_kvm_facility(vcpu->kvm, 76))
>   		return;

--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany