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 bff4d50f0e..1362e43983 100644
--- a/qapi/machine-target.json
+++ b/qapi/machine-target.json
@@ -412,3 +412,36 @@
   '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": "horizontal" },
+#      "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 dfc4cb42a4..69f31db4af 100644
--- a/hw/s390x/cpu-topology.c
+++ b/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.
@@ -137,6 +138,7 @@ 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;
-- 
2.31.1

On Fri, 2023-06-30 at 11:17 +0200, Pierre Morel wrote:
> 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: Nina Schoetterl-Glausch <nsg@linux.ibm.com>

On 7/18/23 09:59, Nina Schoetterl-Glausch wrote:
> On Fri, 2023-06-30 at 11:17 +0200, Pierre Morel wrote:
>> 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: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
>
Thanks,

Pierre

On 30/06/2023 11.17, Pierre Morel wrote:
> 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(+)

Reviewed-by: Thomas Huth <thuth@redhat.com>

On 7/4/23 15:04, Thomas Huth wrote:
> On 30/06/2023 11.17, Pierre Morel wrote:
>> 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(+)
>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
>
Thanks,

Pierre