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

Tony Krowiak
2018-04-17T15:09:54Z

On 04/16/2018 07:13 AM, Pierre Morel wrote:
> On 16/04/2018 12:51, 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?
>>
>> 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
>
> If I misunderstood and FEAT_AP really mean AP instructions available
> in the guest,
> same question:
> is this function called if AP instructions are not available in the
> guest?
>
>>
>>> + 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?
>
> sorry, I should have written AP instructions here:
> is this function called if AP instructions are not available in the guest?

Yes, as I stated in a previous email, this function is called by
kvm_arch_vcpu_setup(vcpu) regardless of whether AP instructions are
available on the guest or not.

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