diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 278ee00..c6366cf 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -236,8 +236,7 @@
 		VCPU_EVENT(vcpu, 4, "interrupt: set prefix to %x",
 			   inti->prefix.address);
 		vcpu->stat.deliver_prefix_signal++;
-		vcpu->arch.sie_block->prefix = inti->prefix.address;
-		vcpu->arch.sie_block->ihcpu = 0xffff;
+		kvm_s390_set_prefix(vcpu, inti->prefix.address);
 		break;
 
 	case KVM_S390_RESTART:
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index a33b444..1868b89 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -322,8 +322,7 @@
 	/* this equals initial cpu reset in pop, but we don't switch to ESA */
 	vcpu->arch.sie_block->gpsw.mask = 0UL;
 	vcpu->arch.sie_block->gpsw.addr = 0UL;
-	vcpu->arch.sie_block->prefix    = 0UL;
-	vcpu->arch.sie_block->ihcpu     = 0xffff;
+	kvm_s390_set_prefix(vcpu, 0);
 	vcpu->arch.sie_block->cputm     = 0UL;
 	vcpu->arch.sie_block->ckc       = 0UL;
 	vcpu->arch.sie_block->todpr     = 0;
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 62aa5f1..ff28f9d 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -58,6 +58,13 @@
 	return 0;
 #endif
 }
+
+static inline void kvm_s390_set_prefix(struct kvm_vcpu *vcpu, u32 prefix)
+{
+	vcpu->arch.sie_block->prefix = prefix & 0x7fffe000u;
+	vcpu->arch.sie_block->ihcpu  = 0xffff;
+}
+
 int kvm_s390_handle_wait(struct kvm_vcpu *vcpu);
 enum hrtimer_restart kvm_s390_idle_wakeup(struct hrtimer *timer);
 void kvm_s390_tasklet(unsigned long parm);
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index d026389..9c83b8a 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -56,8 +56,7 @@
 		goto out;
 	}
 
-	vcpu->arch.sie_block->prefix = address;
-	vcpu->arch.sie_block->ihcpu = 0xffff;
+	kvm_s390_set_prefix(vcpu, address);
 
 	VCPU_EVENT(vcpu, 5, "setting prefix to %x", address);
 out: