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

Pierre Morel
2018-04-16T10:51:46Z

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@linux.vnet.ibm.com>
> ---
> 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 Böblingen - Germany