From: Pierre Morel <pmorel@linux.ibm.com>

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

The feature is disabled by default and fenced for SE
(secure execution).

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20231016183925.2384704-9-nsg@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 hw/s390x/cpu-topology.c   | 2 +-
 target/s390x/cpu_models.c | 1 +
 target/s390x/kvm/kvm.c    | 9 +++++++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
index a00a4ce4df..4e4c35f6da 100644
--- a/hw/s390x/cpu-topology.c
+++ b/hw/s390x/cpu-topology.c
@@ -69,7 +69,7 @@ static int s390_socket_nb(S390CPU *cpu)
  */
 bool s390_has_topology(void)
 {
-    return false;
+    return s390_has_feat(S390_FEAT_CONFIGURATION_TOPOLOGY);
 }
 
 /**
diff --git a/target/s390x/cpu_models.c b/target/s390x/cpu_models.c
index 98f14c09c2..4dead48650 100644
--- a/target/s390x/cpu_models.c
+++ b/target/s390x/cpu_models.c
@@ -255,6 +255,7 @@ bool s390_has_feat(S390Feat feat)
         case S390_FEAT_SIE_CMMA:
         case S390_FEAT_SIE_PFMFI:
         case S390_FEAT_SIE_IBS:
+        case S390_FEAT_CONFIGURATION_TOPOLOGY:
             return false;
             break;
         default:
diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index 4d84dcc018..2e43dc746f 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -366,6 +366,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
     kvm_vm_enable_cap(s, KVM_CAP_S390_USER_SIGP, 0);
     kvm_vm_enable_cap(s, KVM_CAP_S390_VECTOR_REGISTERS, 0);
     kvm_vm_enable_cap(s, KVM_CAP_S390_USER_STSI, 0);
+    kvm_vm_enable_cap(s, KVM_CAP_S390_CPU_TOPOLOGY, 0);
     if (ri_allowed()) {
         if (kvm_vm_enable_cap(s, KVM_CAP_S390_RI, 0) == 0) {
             cap_ri = 1;
@@ -2509,6 +2510,14 @@ void kvm_s390_get_host_cpu_model(S390CPUModel *model, Error **errp)
         set_bit(S390_FEAT_UNPACK, model->features);
     }
 
+    /*
+     * If we have kernel support for CPU Topology indicate the
+     * configuration-topology facility.
+     */
+    if (kvm_check_extension(kvm_state, KVM_CAP_S390_CPU_TOPOLOGY)) {
+        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);
-- 
2.41.0