Messages in this thread | | | Subject | Re: [PATCH v10 24/26] KVM: s390: device attrs to enable/disable AP interpretation | From | Tony Krowiak <> | Date | Mon, 24 Sep 2018 12:25:12 -0400 |
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On 09/24/2018 07:23 AM, David Hildenbrand wrote: > 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)
Given that this patch DOES expose KVM_S390_VM_CRYPTO_ENABLE_APIE only if supported by HW, I assume you are talking about KVM_S390_VM_CRYPTO_DISABLE_APIE. I didn't check ap_instructions_available() for disabling APIE because I didn't think it necessary given that ECA.28 will be set to 0 (intercept) by default, whether AP instructions are installed or not; so why not allow disabling apie. I suppose from the perspective of consistency, since the kvm_s390_vm_has_attr() function checks ap_instructions_available() for both attributes, then it probably makes sense to add that check to KVM_S390_VM_CRYPTO_DISABLE_APIE here. Then again, we could make a change in ap_instructions_available() to allow KVM_S390_VM_CRYPTO_DISABLE_APIE regardless of whether AP instructions are available. It boils down to whether APIE needs to be dynamically disabled at some point when it has been enabled. The only case I can think of where that may be necessary is if a guest is migrated to a system without AP instructions. I don't think that can happen and may even be protected against precisely because the VM attributes won't be available on the target system due to no AP instructions. What say you?
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