KVM: s390: Use kvm_get_vcpu() instead of open-coded access

As we are about to change the way vcpus are allocated, mandate
the use of kvm_get_vcpu() instead of open-coding the access.
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Message-Id: <20211116160403.4074052-4-maz@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/s390/kvm/kvm-s390.c

@@ -4574,7 +4574,7 @@ int kvm_s390_vcpu_start(struct kvm_vcpu *vcpu)
 	}
 
 	for (i = 0; i < online_vcpus; i++) {
-		if (!is_vcpu_stopped(vcpu->kvm->vcpus[i]))
+		if (!is_vcpu_stopped(kvm_get_vcpu(vcpu->kvm, i)))
 			started_vcpus++;
 	}
 
@@ -4636,9 +4636,11 @@ int kvm_s390_vcpu_stop(struct kvm_vcpu *vcpu)
 	__disable_ibs_on_vcpu(vcpu);
 
 	for (i = 0; i < online_vcpus; i++) {
-		if (!is_vcpu_stopped(vcpu->kvm->vcpus[i])) {
+		struct kvm_vcpu *tmp = kvm_get_vcpu(vcpu->kvm, i);
+
+		if (!is_vcpu_stopped(tmp)) {
 			started_vcpus++;
-			started_vcpu = vcpu->kvm->vcpus[i];
+			started_vcpu = tmp;
 		}
 	}