KVM: s390: introduce AIS capability

Introduce a cap to enable AIS facility bit, and add documentation
for this capability.

Signed-off-by: Yi Min Zhao <zyimin@linux.vnet.ibm.com>
Signed-off-by: Fei Li <sherrylf@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

Documentation/virtual/kvm/api.txt

@@ -4110,6 +4110,14 @@ Returns: 0 on success; -EINVAL if the machine does not support
 
 Allows use of guarded storage for the KVM guest.
 
+7.10 KVM_CAP_S390_AIS
+
+Architectures: s390
+Parameters: none
+
+Allow use of adapter-interruption suppression.
+Returns: 0 on success; -EBUSY if a VCPU has already been created.
+
 8. Other capabilities.
 ----------------------
 

arch/s390/kvm/kvm-s390.c

@@ -380,6 +380,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_S390_SKEYS:
 	case KVM_CAP_S390_IRQ_STATE:
 	case KVM_CAP_S390_USER_INSTR0:
+	case KVM_CAP_S390_AIS:
 		r = 1;
 		break;
 	case KVM_CAP_S390_MEM_OP:
@@ -544,6 +545,20 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
 		VM_EVENT(kvm, 3, "ENABLE: CAP_S390_RI %s",
 			 r ? "(not available)" : "(success)");
 		break;
+	case KVM_CAP_S390_AIS:
+		mutex_lock(&kvm->lock);
+		if (kvm->created_vcpus) {
+			r = -EBUSY;
+		} else {
+			set_kvm_facility(kvm->arch.model.fac_mask, 72);
+			set_kvm_facility(kvm->arch.model.fac_list, 72);
+			kvm->arch.float_int.ais_enabled = 1;
+			r = 0;
+		}
+		mutex_unlock(&kvm->lock);
+		VM_EVENT(kvm, 3, "ENABLE: AIS %s",
+			 r ? "(not available)" : "(success)");
+		break;
 	case KVM_CAP_S390_GS:
 		r = -EINVAL;
 		mutex_lock(&kvm->lock);

include/uapi/linux/kvm.h

@@ -884,6 +884,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_PPC_MMU_HASH_V3 135
 #define KVM_CAP_IMMEDIATE_EXIT 136
 #define KVM_CAP_S390_GS 137
+#define KVM_CAP_S390_AIS 138
 
 #ifdef KVM_CAP_IRQ_ROUTING