qapi/s390x/cpu topology: CPU_POLARIZATION_CHANGE QAPI event

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>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Co-developed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Message-ID: <20231016183925.2384704-13-nsg@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

hw/s390x/cpu-topology.c

@@ -24,6 +24,7 @@
 #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.
@@ -136,6 +137,7 @@ void s390_handle_ptf(S390CPU *cpu, uint8_t r1, uintptr_t ra)
         } else {
             s390_topology.polarization = polarization;
             s390_cpu_topology_set_changed(true);
+            qapi_event_send_cpu_polarization_change(polarization);
             setcc(cpu, 0);
         }
         break;

qapi/machine-target.json

@@ -417,3 +417,38 @@
   'features': [ 'unstable' ],
   'if': { 'all': [ 'TARGET_S390X' , 'CONFIG_KVM' ] }
 }
+
+##
+# @CPU_POLARIZATION_CHANGE:
+#
+# Emitted when the guest asks to change the polarization.
+#
+# 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.
+#
+# @polarization: polarization specified by the guest
+#
+# Features:
+#
+# @unstable: This event is experimental.
+#
+# Since: 8.2
+#
+# Example:
+#
+# <- { "event": "CPU_POLARIZATION_CHANGE",
+#      "data": { "polarization": "horizontal" },
+#      "timestamp": { "seconds": 1401385907, "microseconds": 422329 } }
+##
+{ 'event': 'CPU_POLARIZATION_CHANGE',
+  'data': { 'polarization': 'CpuS390Polarization' },
+  'features': [ 'unstable' ],
+  'if': { 'all': [ 'TARGET_S390X', 'CONFIG_KVM' ] }
+}