KVM: s390: enable host-protection-interruption only with ESOP

host-protection-interruption control was introduced with ESOP. So let's
enable it only if we have ESOP and add an explanatory comment why
we can live without it.

Reviewed-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>

arch/s390/kvm/kvm-s390.c

@@ -1837,7 +1837,9 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
 
 	kvm_s390_vcpu_setup_model(vcpu);
 
-	vcpu->arch.sie_block->ecb = 0x02;
+	/* pgste_set_pte has special handling for !MACHINE_HAS_ESOP */
+	if (MACHINE_HAS_ESOP)
+		vcpu->arch.sie_block->ecb |= 0x02;
 	if (test_kvm_facility(vcpu->kvm, 9))
 		vcpu->arch.sie_block->ecb |= 0x04;
 	if (test_kvm_facility(vcpu->kvm, 50) && test_kvm_facility(vcpu->kvm, 73))