s390x/kvm: enable AP instruction interpretation for guest

Let's use the KVM_SET_DEVICE_ATTR ioctl to enable hardware
interpretation of AP instructions executed on the guest.
If the S390_FEAT_AP feature is switched on for the guest,
AP instructions must be interpreted by default; otherwise,
they will be intercepted.

This attribute setting may be overridden by a device. For example,
a device may want to provide AP instructions to the guest (i.e.,
S390_FEAT_AP turned on), but it may want to emulate them. In this
case, the AP instructions executed on the guest must be
intercepted; so when the device is realized, it must disable
interpretation.

Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Tested-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Halil Pasic <pasic@linux.ibm.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <20181010170309.12045-4-akrowiak@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

target/s390x/kvm.c

@@ -2299,11 +2299,26 @@ void kvm_s390_get_host_cpu_model(S390CPUModel *model, Error **errp)
         error_setg(errp, "KVM: host CPU model could not be identified");
         return;
     }
+    /* for now, we can only provide the AP feature with HW support */
+    if (kvm_vm_check_attr(kvm_state, KVM_S390_VM_CRYPTO,
+        KVM_S390_VM_CRYPTO_ENABLE_APIE)) {
+        set_bit(S390_FEAT_AP, model->features);
+    }
     /* strip of features that are not part of the maximum model */
     bitmap_and(model->features, model->features, model->def->full_feat,
                S390_FEAT_MAX);
 }
 
+static void kvm_s390_configure_apie(bool interpret)
+{
+    uint64_t attr = interpret ? KVM_S390_VM_CRYPTO_ENABLE_APIE :
+                                KVM_S390_VM_CRYPTO_DISABLE_APIE;
+
+    if (kvm_vm_check_attr(kvm_state, KVM_S390_VM_CRYPTO, attr)) {
+        kvm_s390_set_attr(attr);
+    }
+}
+
 void kvm_s390_apply_cpu_model(const S390CPUModel *model, Error **errp)
 {
     struct kvm_s390_vm_cpu_processor prop  = {
@@ -2353,6 +2368,10 @@ void kvm_s390_apply_cpu_model(const S390CPUModel *model, Error **errp)
     if (test_bit(S390_FEAT_CMM, model->features)) {
         kvm_s390_enable_cmma();
     }
+
+    if (test_bit(S390_FEAT_AP, model->features)) {
+        kvm_s390_configure_apie(true);
+    }
 }
 
 void kvm_s390_restart_interrupt(S390CPU *cpu)