KVM: s390: Verify memory in kvm run

This check verifies that the guest we're trying to run in KVM_RUN
has some memory assigned to it. It enters an endless exception
loop if this is not the case.
Reported-by: Mijo Safradin <mijo@linux.vnet.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Christian Ehrhardt <ehrhardt@de.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/s390/kvm/kvm-s390.c

@@ -487,6 +487,12 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 
 	vcpu_load(vcpu);
 
+	/* verify, that memory has been registered */
+	if (!vcpu->kvm->arch.guest_memsize) {
+		vcpu_put(vcpu);
+		return -EINVAL;
+	}
+
 	if (vcpu->sigset_active)
 		sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved);