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

Tony Krowiak
2018-09-24T18:42:48Z

On 09/24/2018 12:25 PM, Tony Krowiak wrote:
> On 09/24/2018 07:23 AM, David Hildenbrand wrote:

(...)

>> 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?
>
David,

I'm sorry, I misinterpreted what you were asking for. Check out the
fixup! patch below and let me know if that is what you are looking for.
If so, I will integrate that change and post v11 tomorrow (Tuesday 9/24).

-----------------------------------8<-----------------------------------

From: Tony Krowiak <akrowiak@linux.ibm.com>
Date: Mon, 24 Sep 2018 14:18:37 -0400
Subject: [FIXUP v10] fixup! KVM: s390: device attrs to enable/disable AP
interpretation

---
arch/s390/kvm/kvm-s390.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 6654bb1fc26a..a528558baa78 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -901,6 +901,10 @@ static int kvm_s390_vm_set_crypto(struct kvm *kvm,
struct kvm_device_attr *attr)
kvm->arch.crypto.apie = 1;
break;
case KVM_S390_VM_CRYPTO_DISABLE_APIE:
+ if (!ap_instructions_available()) {
+ mutex_unlock(&kvm->lock);
+ return -EOPNOTSUPP;
+ }
kvm->arch.crypto.apie = 0;
break;
default:
@@ -1509,9 +1513,11 @@ 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:
+ ret = 0;
+ break;
case KVM_S390_VM_CRYPTO_ENABLE_APIE:
case KVM_S390_VM_CRYPTO_DISABLE_APIE:
- ret = 0;
+ ret = ap_instructions_available();
break;
default:
ret = -ENXIO;
@@ -2620,6 +2626,7 @@ 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->ecb3 &= ~(ECB3_AES | ECB3_DEA);
+ vcpu->kvm->arch.crypto.apie &= ~ECA_APIE;

if (vcpu->kvm->arch.crypto.apie)
vcpu->arch.sie_block->eca |= ECA_APIE;
--
2.19.0.221.g150f307

>>
>