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Subject: Re: [PATCH v10 24/26] KVM: s390: device attrs to enable/disable AP
 interpretation
To:     David Hildenbrand <david@redhat.com>,
        Tony Krowiak <akrowiak@linux.vnet.ibm.com>,
        linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Cc:     freude@de.ibm.com, schwidefsky@de.ibm.com,
        heiko.carstens@de.ibm.com, borntraeger@de.ibm.com,
        cohuck@redhat.com, kwankhede@nvidia.com,
        bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com,
        alex.williamson@redhat.com, pmorel@linux.vnet.ibm.com,
        alifm@linux.vnet.ibm.com, mjrosato@linux.vnet.ibm.com,
        jjherne@linux.vnet.ibm.com, thuth@redhat.com,
        pasic@linux.vnet.ibm.com, berrange@redhat.com,
        fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com,
        frankja@linux.ibm.com
References: <1536781396-13601-1-git-send-email-akrowiak@linux.vnet.ibm.com>
 <1536781396-13601-25-git-send-email-akrowiak@linux.vnet.ibm.com>
 <9263b698-1827-1b7f-28bf-75b44657dea2@redhat.com>
From:   Tony Krowiak <akrowiak@linux.ibm.com>
Date:   Fri, 21 Sep 2018 19:40:36 -0400
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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.

>