When the guest asks to change the polarization this change
is forwarded to the upper layer using QAPI.
The upper layer is supposed to take according decisions concerning
CPU provisioning.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
---
 qapi/machine-target.json | 33 +++++++++++++++++++++++++++++++++
 hw/s390x/cpu-topology.c  |  2 ++
 2 files changed, 35 insertions(+)

diff --git a/qapi/machine-target.json b/qapi/machine-target.json
index 3b7a0b77f4..ffde2e9cbd 100644
--- a/qapi/machine-target.json
+++ b/qapi/machine-target.json
@@ -391,3 +391,36 @@
   'features': [ 'unstable' ],
   'if': { 'all': [ 'TARGET_S390X' , 'CONFIG_KVM' ] }
 }
+
+##
+# @CPU_POLARIZATION_CHANGE:
+#
+# Emitted when the guest asks to change the polarization.
+#
+# @polarization: polarization specified by the guest
+#
+# Features:
+# @unstable: This command may still be modified.
+#
+# The guest can tell the host (via the PTF instruction) whether the
+# CPUs should be provisioned using horizontal or vertical polarization.
+#
+# On horizontal polarization the host is expected to provision all vCPUs
+# equally.
+# On vertical polarization the host can provision each vCPU differently.
+# The guest will get information on the details of the provisioning
+# the next time it uses the STSI(15) instruction.
+#
+# Since: 8.1
+#
+# Example:
+#
+# <- { "event": "CPU_POLARIZATION_CHANGE",
+#      "data": { "polarization": 0 },
+#      "timestamp": { "seconds": 1401385907, "microseconds": 422329 } }
+##
+{ 'event': 'CPU_POLARIZATION_CHANGE',
+  'data': { 'polarization': 'CpuS390Polarization' },
+  'features': [ 'unstable' ],
+  'if': { 'all': [ 'TARGET_S390X', 'CONFIG_KVM' ] }
+}
diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
index 1cf3adec31..39c6d262e3 100644
--- a/hw/s390x/cpu-topology.c
+++ b/hw/s390x/cpu-topology.c
@@ -19,6 +19,7 @@
 #include "hw/s390x/s390-virtio-ccw.h"
 #include "hw/s390x/cpu-topology.h"
 #include "qapi/qapi-commands-machine-target.h"
+#include "qapi/qapi-events-machine-target.h"
 
 /*
  * s390_topology is used to keep the topology information.
@@ -160,6 +161,7 @@ void s390_handle_ptf(S390CPU *cpu, uint8_t r1, uintptr_t ra)
             s390_topology.polarization = fc;
             s390_topology_set_cpus_entitlement();
             s390_cpu_topology_set_changed(true);
+            qapi_event_send_cpu_polarization_change(fc);
             setcc(cpu, 0);
         }
         break;
-- 
2.31.1