Re: [PATCH v10 24/26] KVM: s390: device attrs to enable/disable AP interpretation

David Hildenbrand
2018-09-24T11:23:42Z

On 22/09/2018 01:40, Tony Krowiak wrote:
> On 09/17/2018 04:51 AM, David Hildenbrand wrote:
>> Am 12.09.18 um 21:43 schrieb Tony Krowiak:
>>> From: Tony Krowiak <akrowiak@linux.ibm.com>
>>>
>>> Introduces two new VM crypto device attributes (KVM_S390_VM_CRYPTO)
>>> to enable or disable AP instruction interpretation from userspace
>>> via the KVM_SET_DEVICE_ATTR ioctl:
>>>
>>> * The KVM_S390_VM_CRYPTO_ENABLE_APIE attribute enables hardware
>>> interpretation of AP instructions executed on the guest.
>>>
>>> * The KVM_S390_VM_CRYPTO_DISABLE_APIE attribute disables hardware
>>> interpretation of AP instructions executed on the guest. In this
>>> case the instructions will be intercepted and pass through to
>>> the guest.
>>>
>>> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
>>> ---
>>> arch/s390/include/asm/kvm_host.h | 1 +
>>> arch/s390/include/uapi/asm/kvm.h | 2 ++
>>> arch/s390/kvm/kvm-s390.c | 27 +++++++++++++++++++++++----
>>> 3 files changed, 26 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
>>> index b32bd1b..36d3531 100644
>>> --- a/arch/s390/include/asm/kvm_host.h
>>> +++ b/arch/s390/include/asm/kvm_host.h
>>> @@ -719,6 +719,7 @@ struct kvm_s390_crypto {
>>> __u32 crycbd;
>>> __u8 aes_kw;
>>> __u8 dea_kw;
>>> + __u8 apie;
>>> };
>>>
>>> #define APCB0_MASK_SIZE 1
>>> diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
>>> index 8c23afc..a8dbd90 100644
>>> --- a/arch/s390/include/uapi/asm/kvm.h
>>> +++ b/arch/s390/include/uapi/asm/kvm.h
>>> @@ -161,6 +161,8 @@ struct kvm_s390_vm_cpu_subfunc {
>>> #define KVM_S390_VM_CRYPTO_ENABLE_DEA_KW 1
>>> #define KVM_S390_VM_CRYPTO_DISABLE_AES_KW 2
>>> #define KVM_S390_VM_CRYPTO_DISABLE_DEA_KW 3
>>> +#define KVM_S390_VM_CRYPTO_ENABLE_APIE 4
>>> +#define KVM_S390_VM_CRYPTO_DISABLE_APIE 5
>>>
>>> /* kvm attributes for migration mode */
>>> #define KVM_S390_VM_MIGRATION_STOP 0
>>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>>> index 2cdd980..286c2e0 100644
>>> --- a/arch/s390/kvm/kvm-s390.c
>>> +++ b/arch/s390/kvm/kvm-s390.c
>>> @@ -856,12 +856,11 @@ void kvm_s390_vcpu_crypto_reset_all(struct kvm *kvm)
>>>
>>> static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr)
>>> {
>>> - if (!test_kvm_facility(kvm, 76))
>>> - return -EINVAL;
>>> -
>>> mutex_lock(&kvm->lock);
>>> switch (attr->attr) {
>>> case KVM_S390_VM_CRYPTO_ENABLE_AES_KW:
>>> + if (!test_kvm_facility(kvm, 76))
>>> + return -EINVAL;
>>> get_random_bytes(
>>> kvm->arch.crypto.crycb->aes_wrapping_key_mask,
>>> sizeof(kvm->arch.crypto.crycb->aes_wrapping_key_mask));
>>> @@ -869,6 +868,8 @@ static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr)
>>> VM_EVENT(kvm, 3, "%s", "ENABLE: AES keywrapping support");
>>> break;
>>> case KVM_S390_VM_CRYPTO_ENABLE_DEA_KW:
>>> + if (!test_kvm_facility(kvm, 76))
>>> + return -EINVAL;
>>> get_random_bytes(
>>> kvm->arch.crypto.crycb->dea_wrapping_key_mask,
>>> sizeof(kvm->arch.crypto.crycb->dea_wrapping_key_mask));
>>> @@ -876,17 +877,31 @@ static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr)
>>> VM_EVENT(kvm, 3, "%s", "ENABLE: DEA keywrapping support");
>>> break;
>>> case KVM_S390_VM_CRYPTO_DISABLE_AES_KW:
>>> + if (!test_kvm_facility(kvm, 76))
>>> + return -EINVAL;
>>> kvm->arch.crypto.aes_kw = 0;
>>> memset(kvm->arch.crypto.crycb->aes_wrapping_key_mask, 0,
>>> sizeof(kvm->arch.crypto.crycb->aes_wrapping_key_mask));
>>> VM_EVENT(kvm, 3, "%s", "DISABLE: AES keywrapping support");
>>> break;
>>> case KVM_S390_VM_CRYPTO_DISABLE_DEA_KW:
>>> + if (!test_kvm_facility(kvm, 76))
>>> + return -EINVAL;
>>> kvm->arch.crypto.dea_kw = 0;
>>> memset(kvm->arch.crypto.crycb->dea_wrapping_key_mask, 0,
>>> sizeof(kvm->arch.crypto.crycb->dea_wrapping_key_mask));
>>> VM_EVENT(kvm, 3, "%s", "DISABLE: DEA keywrapping support");
>>> break;
>>> + case KVM_S390_VM_CRYPTO_ENABLE_APIE:
>>> + if (!ap_instructions_available()) {
>>> + mutex_unlock(&kvm->lock);
>>> + return -EOPNOTSUPP;
>>> + }
>>> + kvm->arch.crypto.apie = 1;
>>> + break;
>>> + case KVM_S390_VM_CRYPTO_DISABLE_APIE:
>>> + kvm->arch.crypto.apie = 0;
>>> + break;
>>> default:
>>> mutex_unlock(&kvm->lock);
>>> return -ENXIO;
>>> @@ -1493,6 +1508,8 @@ static int kvm_s390_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
>>> case KVM_S390_VM_CRYPTO_ENABLE_DEA_KW:
>>> case KVM_S390_VM_CRYPTO_DISABLE_AES_KW:
>>> case KVM_S390_VM_CRYPTO_DISABLE_DEA_KW:
>>> + case KVM_S390_VM_CRYPTO_ENABLE_APIE:
>>> + case KVM_S390_VM_CRYPTO_DISABLE_APIE:
>>
>> As also replied to the QEMU series, could we indicate
>> KVM_S390_VM_CRYPTO_ENABLE_APIE (and maybe
>> KVM_S390_VM_CRYPTO_DISABLE_APIE) only with ap_instructions_available(),
>> so we can avoid the additional KVM_S390_VM_CPU_FEAT_AP?
>>
>> KVM_S390_VM_CPU_FEAT_AP is right now completely unused in KVM otherwise
>> (never checked, we only care about apie).
>
> After much discussion with Halil and a few exchanges with you, we
> decided to go ahead and accept your suggestion to get rid of
> KVM_S390_VM_CPU_FEAT and keep the VM device attributes to enable/disable
> apie.
>
> To that end, I responded to patches 03/26, 11/26 and 25/26 with fixup!
> patches that show the KVM/kernel changes that will be necessary to get
> rid of KVM_S390_VM_CPU_FEAT and use apie to control ECA.28. I did that
> to generate discussion in v10 rather than waiting until v11 for
> comments. I make no guarantees that those fixup! patches will
> successfully apply should you have a v10 branch generated from this
> patch series you want to update.
>

Will you also fixup this patch to expose KVM_S390_VM_CRYPTO_ENABLE_APIE
only if supported by HW? (ap_instructions_available)

--

Thanks,

David / dhildenb