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SubjectRe: [PATCH v4 05/15] KVM: s390: enable/disable AP interpretive execution
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On 04/16/2018 06:51 AM, Pierre Morel wrote:
> 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?

Yes we do.

>
>
> 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

KVM_S390_VM_CPU_FEAT_AP does NOT mean AP instructions are interpreted,
it means
AP instructions are installed.

>
>> + 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?

Yes, kvm_s390_vcpu_crypto_setup(vcpu) is called by kvm_arch_vcpu_setup(vcpu)
as well as from kvm_s390_vcpu_crypto_reset_all(kvm). Calling it has nothing
to do with whether AP interpretation is supported or not as it does much
more than that, including setting up of wrapping keys and the CRYCBD.

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

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