KVM: s390: vsie: support shared IPTE-interlock facility

As we forward the whole SCA provided by guest 2, we can directly forward
SIIF if available.

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index e0c5a57..d735612 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -267,6 +267,8 @@
 	allow_cpu_feat(KVM_S390_VM_CPU_FEAT_SIEF2);
 	if (sclp.has_64bscao)
 		allow_cpu_feat(KVM_S390_VM_CPU_FEAT_64BSCAO);
+	if (sclp.has_siif)
+		allow_cpu_feat(KVM_S390_VM_CPU_FEAT_SIIF);
 }
 
 int kvm_arch_init(void *opaque)