KVM: s390: fast path for sca_ext_call_pending

If CPUSTAT_ECALL_PEND isn't set, we can't have an external call pending,
so we can directly avoid taking the lock.
Acked-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>

arch/s390/kvm/interrupt.c

@@ -39,6 +39,9 @@ static int sca_ext_call_pending(struct kvm_vcpu *vcpu, int *src_id)
 {
 	int c, scn;
 
+	if (!(atomic_read(&vcpu->arch.sie_block->cpuflags) & CPUSTAT_ECALL_PEND))
+		return 0;
+
 	read_lock(&vcpu->kvm->arch.sca_lock);
 	if (vcpu->kvm->arch.use_esca) {
 		struct esca_block *sca = vcpu->kvm->arch.sca;
@@ -60,8 +63,7 @@ static int sca_ext_call_pending(struct kvm_vcpu *vcpu, int *src_id)
 	if (src_id)
 		*src_id = scn;
 
-	return c && atomic_read(&vcpu->arch.sie_block->cpuflags) &
-			CPUSTAT_ECALL_PEND;
+	return c;
 }
 
 static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id)