The KVM capability, KVM_CAP_S390_CPU_TOPOLOGY is used to
activate the S390_FEAT_CONFIGURATION_TOPOLOGY feature and
the topology facility for the guest in the case the topology
is available in QEMU and in KVM.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
---
 target/s390x/kvm/kvm.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index 49a99931a4..1c4e24c9a7 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -2464,6 +2464,22 @@ void kvm_s390_get_host_cpu_model(S390CPUModel *model, Error **errp)
         set_bit(S390_FEAT_UNPACK, model->features);
     }
 
+    /*
+     * If we have the CPU Topology allowed in QEMU and
+     * implemented in KVM, activate the CPU TOPOLOGY feature.
+     */
+    if (s390_has_topology()) {
+        if (!kvm_check_extension(kvm_state, KVM_CAP_S390_CPU_TOPOLOGY)) {
+            error_setg(errp, "KVM: S390 topology not present in kernel");
+            return;
+        }
+        if (kvm_vm_enable_cap(kvm_state, KVM_CAP_S390_CPU_TOPOLOGY, 0) < 0) {
+            error_setg(errp, "KVM: Error enabling KVM_CAP_S390_CPU_TOPOLOGY");
+            return;
+        }
+        set_bit(S390_FEAT_CONFIGURATION_TOPOLOGY, model->features);
+    }
+
     /* We emulate a zPCI bus and AEN, therefore we don't need HW support */
     set_bit(S390_FEAT_ZPCI, model->features);
     set_bit(S390_FEAT_ADAPTER_EVENT_NOTIFICATION, model->features);
-- 
2.31.1