[PATCH v4 0/4] Add SCLP event type CPI

[PATCH v4 0/4] Add SCLP event type CPI

[Shalini Chellathurai Saroja]

Implement the Service-Call Logical Processor (SCLP) event
type Control-Program Identification (CPI) in QEMU.

Changed since v3:
- Add QOM object sclpcpi from ccw_init()
- Add SCLPEventCPI state to store the CPI data in the sclpcpi device
- Other minor changes

Changed since v2:
- Add SPDX license tag in the new file hw/s390x/sclpcpi.c
- Store the control-program Identification data in the sclpcpi device
- Update the description of CPI attributes
- Use ldq_be_p() intead of be64_to_cpu()
- Return the CPI attribute system-level as an integer in QMP
- Add compat handling for backward migration
- Other minor changes

Shalini Chellathurai Saroja (4):
  hw/s390x: add SCLP event type CPI
  hw/s390x: add Control-Program Identification to QOM
  hw/s390x: support migration of CPI data
  hw/s390x: compat handling for backward migration

 hw/s390x/event-facility.c          |   2 +
 hw/s390x/meson.build               |   1 +
 hw/s390x/s390-virtio-ccw.c         |  22 ++++
 hw/s390x/sclpcpi.c                 | 156 +++++++++++++++++++++++++++++
 include/hw/s390x/event-facility.h  |  22 ++++
 include/hw/s390x/s390-virtio-ccw.h |   1 +
 qapi/machine.json                  |  58 +++++++++++
 7 files changed, 262 insertions(+)
 create mode 100644 hw/s390x/sclpcpi.c

-- 
2.49.0

[PATCH v4 1/4] hw/s390x: add SCLP event type CPI

[Shalini Chellathurai Saroja]

Implement the Service-Call Logical Processor (SCLP) event
type Control-Program Identification (CPI) in QEMU. This
event is used to send CPI identifiers from the guest to the
host. The CPI identifiers are: system type, system name,
system level and sysplex name.

System type: operating system of the guest (e.g. "LINUX").
System name: user configurable name of the guest (e.g. "TESTVM").
System level: distribution and kernel version, if the system type is Linux
(e.g. 0x50e00).
Sysplex name: name of the cluster which the guest belongs to (if any)
(e.g. "PLEX").

Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
---
 hw/s390x/event-facility.c         |  2 +
 hw/s390x/meson.build              |  1 +
 hw/s390x/s390-virtio-ccw.c        | 14 +++++
 hw/s390x/sclpcpi.c                | 92 +++++++++++++++++++++++++++++++
 include/hw/s390x/event-facility.h | 13 +++++
 5 files changed, 122 insertions(+)
 create mode 100644 hw/s390x/sclpcpi.c

diff --git a/hw/s390x/event-facility.c b/hw/s390x/event-facility.c
index 2b0332c20e..60237b8581 100644
--- a/hw/s390x/event-facility.c
+++ b/hw/s390x/event-facility.c
@@ -4,6 +4,7 @@
  *       handles SCLP event types
  *          - Signal Quiesce - system power down
  *          - ASCII Console Data - VT220 read and write
+ *          - Control-Program Identification - Send OS data from guest to host
  *
  * Copyright IBM, Corp. 2012
  *
@@ -40,6 +41,7 @@ struct SCLPEventFacility {
     SysBusDevice parent_obj;
     SCLPEventsBus sbus;
     SCLPEvent quiesce, cpu_hotplug;
+    SCLPEventCPI cpi;
     /* guest's receive mask */
     union {
         uint32_t receive_mask_pieces[2];
diff --git a/hw/s390x/meson.build b/hw/s390x/meson.build
index 3bbebfd817..eb7950489c 100644
--- a/hw/s390x/meson.build
+++ b/hw/s390x/meson.build
@@ -13,6 +13,7 @@ s390x_ss.add(files(
   's390-skeys.c',
   's390-stattrib.c',
   'sclp.c',
+  'sclpcpi.c',
   'sclpcpu.c',
   'sclpquiesce.c',
   'tod.c',
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 75b32182eb..7f28cbd1de 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -260,6 +260,17 @@ static void s390_create_sclpconsole(SCLPDevice *sclp,
     qdev_realize_and_unref(dev, ev_fac_bus, &error_fatal);
 }
 
+static void s390_create_sclpcpi(SCLPDevice *sclp)
+{
+    SCLPEventFacility *ef = sclp->event_facility;
+    BusState *ev_fac_bus = sclp_get_event_facility_bus(ef);
+    DeviceState *dev;
+
+    dev = qdev_new(TYPE_SCLP_EVENT_CPI);
+    object_property_add_child(OBJECT(ef), "sclpcpi", OBJECT(dev));
+    qdev_realize_and_unref(dev, ev_fac_bus, &error_fatal);
+}
+
 static void ccw_init(MachineState *machine)
 {
     MachineClass *mc = MACHINE_GET_CLASS(machine);
@@ -323,6 +334,9 @@ static void ccw_init(MachineState *machine)
 
     /* init the TOD clock */
     s390_init_tod();
+
+    /* init SCLP event Control-Program Identification */
+    s390_create_sclpcpi(ms->sclp);
 }
 
 static void s390_cpu_plug(HotplugHandler *hotplug_dev,
diff --git a/hw/s390x/sclpcpi.c b/hw/s390x/sclpcpi.c
new file mode 100644
index 0000000000..13589459b1
--- /dev/null
+++ b/hw/s390x/sclpcpi.c
@@ -0,0 +1,92 @@
+ /*
+  * SPDX-License-Identifier: GPL-2.0-or-later
+  *
+  * SCLP event type 11 - Control-Program Identification (CPI):
+  *    CPI is used to send program identifiers from the guest to the
+  *    Service-Call Logical Processor (SCLP). It is not sent by the SCLP.
+  *    Please refer S390ControlProgramId QOM-type description for details
+  *    on the contents of the CPI.
+  *
+  * Copyright IBM, Corp. 2024
+  *
+  * Authors:
+  *  Shalini Chellathurai Saroja <shalini@linux.ibm.com>
+  *
+  * This work is licensed under the terms of the GNU GPL, version 2 or (at your
+  * option) any later version.  See the COPYING file in the top-level directory.
+  *
+  */
+
+#include "qemu/osdep.h"
+#include "hw/s390x/event-facility.h"
+
+typedef struct Data {
+    uint8_t id_format;
+    uint8_t reserved0;
+    uint8_t system_type[8];
+    uint64_t reserved1;
+    uint8_t system_name[8];
+    uint64_t reserved2;
+    uint64_t system_level;
+    uint64_t reserved3;
+    uint8_t sysplex_name[8];
+    uint8_t reserved4[16];
+} QEMU_PACKED Data;
+
+typedef struct ControlProgramIdMsg {
+    EventBufferHeader ebh;
+    Data data;
+} QEMU_PACKED ControlProgramIdMsg;
+
+static bool can_handle_event(uint8_t type)
+{
+    return type == SCLP_EVENT_CTRL_PGM_ID;
+}
+
+static sccb_mask_t send_mask(void)
+{
+    return 0;
+}
+
+/* Enable SCLP to accept buffers of event type CPI from the control-program. */
+static sccb_mask_t receive_mask(void)
+{
+    return SCLP_EVENT_MASK_CTRL_PGM_ID;
+}
+
+static int write_event_data(SCLPEvent *event, EventBufferHeader *evt_buf_hdr)
+{
+    ControlProgramIdMsg *cpim = container_of(evt_buf_hdr, ControlProgramIdMsg,
+                                             ebh);
+
+    cpim->ebh.flags = SCLP_EVENT_BUFFER_ACCEPTED;
+    return SCLP_RC_NORMAL_COMPLETION;
+}
+
+static void cpi_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    SCLPEventClass *k = SCLP_EVENT_CLASS(klass);
+
+    dc->user_creatable = false;
+
+    k->can_handle_event = can_handle_event;
+    k->get_send_mask = send_mask;
+    k->get_receive_mask = receive_mask;
+    k->write_event_data = write_event_data;
+}
+
+static const TypeInfo sclp_cpi_info = {
+    .name          = TYPE_SCLP_EVENT_CPI,
+    .parent        = TYPE_SCLP_EVENT,
+    .instance_size = sizeof(SCLPEventCPI),
+    .class_init    = cpi_class_init,
+};
+
+static void sclp_cpi_register_types(void)
+{
+    type_register_static(&sclp_cpi_info);
+}
+
+type_init(sclp_cpi_register_types)
+
diff --git a/include/hw/s390x/event-facility.h b/include/hw/s390x/event-facility.h
index ff874e792d..ef469e62ae 100644
--- a/include/hw/s390x/event-facility.h
+++ b/include/hw/s390x/event-facility.h
@@ -25,6 +25,7 @@
 #define SCLP_EVENT_MESSAGE                      0x02
 #define SCLP_EVENT_CONFIG_MGT_DATA              0x04
 #define SCLP_EVENT_PMSGCMD                      0x09
+#define SCLP_EVENT_CTRL_PGM_ID                  0x0b
 #define SCLP_EVENT_ASCII_CONSOLE_DATA           0x1a
 #define SCLP_EVENT_SIGNAL_QUIESCE               0x1d
 
@@ -35,6 +36,7 @@
 #define SCLP_EVENT_MASK_MSG             SCLP_EVMASK(SCLP_EVENT_MESSAGE)
 #define SCLP_EVENT_MASK_CONFIG_MGT_DATA SCLP_EVMASK(SCLP_EVENT_CONFIG_MGT_DATA)
 #define SCLP_EVENT_MASK_PMSGCMD         SCLP_EVMASK(SCLP_EVENT_PMSGCMD)
+#define SCLP_EVENT_MASK_CTRL_PGM_ID     SCLP_EVMASK(SCLP_EVENT_CTRL_PGM_ID)
 #define SCLP_EVENT_MASK_MSG_ASCII       SCLP_EVMASK(SCLP_EVENT_ASCII_CONSOLE_DATA)
 #define SCLP_EVENT_MASK_SIGNAL_QUIESCE  SCLP_EVMASK(SCLP_EVENT_SIGNAL_QUIESCE)
 
@@ -191,6 +193,17 @@ struct SCLPEventClass {
     bool (*can_handle_event)(uint8_t type);
 };
 
+#define TYPE_SCLP_EVENT_CPI "sclpcpi"
+typedef struct SCLPEventCPIClass SCLPEventCPIClass;
+typedef struct SCLPEventCPI SCLPEventCPI;
+OBJECT_DECLARE_TYPE(SCLPEventCPI, SCLPEventCPIClass,
+                    SCLP_EVENT_CPI)
+
+struct SCLPEventCPI {
+    DeviceState qdev;
+    SCLPEvent event;
+};
+
 #define TYPE_SCLP_EVENT_FACILITY "s390-sclp-event-facility"
 typedef struct SCLPEventFacility SCLPEventFacility;
 typedef struct SCLPEventFacilityClass SCLPEventFacilityClass;
-- 
2.49.0

Re: [PATCH v4 1/4] hw/s390x: add SCLP event type CPI

[Janis Schoetterl-Glausch]

On Thu, 2025-04-10 at 17:09 +0200, Shalini Chellathurai Saroja wrote:
> Implement the Service-Call Logical Processor (SCLP) event
> type Control-Program Identification (CPI) in QEMU. This
> event is used to send CPI identifiers from the guest to the
> host. The CPI identifiers are: system type, system name,
> system level and sysplex name.
> 
> System type: operating system of the guest (e.g. "LINUX").
> System name: user configurable name of the guest (e.g. "TESTVM").
> System level: distribution and kernel version, if the system type is Linux
> (e.g. 0x50e00).
> Sysplex name: name of the cluster which the guest belongs to (if any)
> (e.g. "PLEX").
> 
> Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> ---
>  hw/s390x/event-facility.c         |  2 +
>  hw/s390x/meson.build              |  1 +
>  hw/s390x/s390-virtio-ccw.c        | 14 +++++
>  hw/s390x/sclpcpi.c                | 92 +++++++++++++++++++++++++++++++
>  include/hw/s390x/event-facility.h | 13 +++++
>  5 files changed, 122 insertions(+)
>  create mode 100644 hw/s390x/sclpcpi.c
> 
> diff --git a/hw/s390x/event-facility.c b/hw/s390x/event-facility.c
> index 2b0332c20e..60237b8581 100644
> --- a/hw/s390x/event-facility.c
> +++ b/hw/s390x/event-facility.c
> @@ -4,6 +4,7 @@
>   *       handles SCLP event types
>   *          - Signal Quiesce - system power down
>   *          - ASCII Console Data - VT220 read and write
> + *          - Control-Program Identification - Send OS data from guest to host
>   *
>   * Copyright IBM, Corp. 2012
>   *
> @@ -40,6 +41,7 @@ struct SCLPEventFacility {
>      SysBusDevice parent_obj;
>      SCLPEventsBus sbus;
>      SCLPEvent quiesce, cpu_hotplug;
> +    SCLPEventCPI cpi;
>      /* guest's receive mask */
>      union {
>          uint32_t receive_mask_pieces[2];
> diff --git a/hw/s390x/meson.build b/hw/s390x/meson.build
> index 3bbebfd817..eb7950489c 100644
> --- a/hw/s390x/meson.build
> +++ b/hw/s390x/meson.build
> @@ -13,6 +13,7 @@ s390x_ss.add(files(
>    's390-skeys.c',
>    's390-stattrib.c',
>    'sclp.c',
> +  'sclpcpi.c',
>    'sclpcpu.c',
>    'sclpquiesce.c',
>    'tod.c',
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index 75b32182eb..7f28cbd1de 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -260,6 +260,17 @@ static void s390_create_sclpconsole(SCLPDevice *sclp,
>      qdev_realize_and_unref(dev, ev_fac_bus, &error_fatal);
>  }
>  
> +static void s390_create_sclpcpi(SCLPDevice *sclp)
> +{
> +    SCLPEventFacility *ef = sclp->event_facility;
> +    BusState *ev_fac_bus = sclp_get_event_facility_bus(ef);
> +    DeviceState *dev;
> +
> +    dev = qdev_new(TYPE_SCLP_EVENT_CPI);
> +    object_property_add_child(OBJECT(ef), "sclpcpi", OBJECT(dev));
> +    qdev_realize_and_unref(dev, ev_fac_bus, &error_fatal);

I wonder if we should drop this and add control-program-id directly
on the event facility. I don't see what purpose having the intermediate
level sclpcpi serves.

> +}

[...]

> diff --git a/include/hw/s390x/event-facility.h b/include/hw/s390x/event-facility.h
> index ff874e792d..ef469e62ae 100644
> --- a/include/hw/s390x/event-facility.h
> +++ b/include/hw/s390x/event-facility.h

[...]
   I. 
> +struct SCLPEventCPI {
> +    DeviceState qdev;
> +    SCLPEvent event;

I think you should just inherit from SCLPEvent, which in turn inherits from DeviceState.
So without the qdev.

> +};
> +
>  #define TYPE_SCLP_EVENT_FACILITY "s390-sclp-event-facility"
>  typedef struct SCLPEventFacility SCLPEventFacility;
>  typedef struct SCLPEventFacilityClass SCLPEventFacilityClass;

-- 
IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Wolfgang Wendt Geschäftsführung: David Faller Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB
243294

Re: [PATCH v4 1/4] hw/s390x: add SCLP event type CPI

[Nina Schoetterl-Glausch]

On Thu, 2025-04-10 at 17:09 +0200, Shalini Chellathurai Saroja wrote:
> Implement the Service-Call Logical Processor (SCLP) event
> type Control-Program Identification (CPI) in QEMU. This
> event is used to send CPI identifiers from the guest to the
> host. The CPI identifiers are: system type, system name,
> system level and sysplex name.
> 
> System type: operating system of the guest (e.g. "LINUX").
> System name: user configurable name of the guest (e.g. "TESTVM").
> System level: distribution and kernel version, if the system type is Linux
> (e.g. 0x50e00).
> Sysplex name: name of the cluster which the guest belongs to (if any)
> (e.g. "PLEX").
> 
> Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> ---
>  hw/s390x/event-facility.c         |  2 +
>  hw/s390x/meson.build              |  1 +
>  hw/s390x/s390-virtio-ccw.c        | 14 +++++
>  hw/s390x/sclpcpi.c                | 92 +++++++++++++++++++++++++++++++
>  include/hw/s390x/event-facility.h | 13 +++++
>  5 files changed, 122 insertions(+)
>  create mode 100644 hw/s390x/sclpcpi.c

[...]


>  static void s390_cpu_plug(HotplugHandler *hotplug_dev,
> diff --git a/hw/s390x/sclpcpi.c b/hw/s390x/sclpcpi.c
> new file mode 100644
> index 0000000000..13589459b1
> --- /dev/null
> +++ b/hw/s390x/sclpcpi.c

[...]

> +static void cpi_class_init(ObjectClass *klass, void *data)

Should be 'const void *data'.

> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    SCLPEventClass *k = SCLP_EVENT_CLASS(klass);
> +
> +    dc->user_creatable = false;
> +
> +    k->can_handle_event = can_handle_event;
> +    k->get_send_mask = send_mask;
> +    k->get_receive_mask = receive_mask;
> +    k->write_event_data = write_event_data;
> +}

[...]

-- 
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Wolfgang Wendt
Geschäftsführung: David Faller
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294

Re: [PATCH v4 1/4] hw/s390x: add SCLP event type CPI

[Shalini Chellathurai Saroja]

On 2025-04-29 11:20, Nina Schoetterl-Glausch wrote:
> On Thu, 2025-04-10 at 17:09 +0200, Shalini Chellathurai Saroja wrote:
>> Implement the Service-Call Logical Processor (SCLP) event
>> type Control-Program Identification (CPI) in QEMU. This
>> event is used to send CPI identifiers from the guest to the
>> host. The CPI identifiers are: system type, system name,
>> system level and sysplex name.
>> 
>> System type: operating system of the guest (e.g. "LINUX").
>> System name: user configurable name of the guest (e.g. "TESTVM").
>> System level: distribution and kernel version, if the system type is 
>> Linux
>> (e.g. 0x50e00).
>> Sysplex name: name of the cluster which the guest belongs to (if any)
>> (e.g. "PLEX").
>> 
>> Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
>> Reviewed-by: Thomas Huth <thuth@redhat.com>
>> ---
>>  hw/s390x/event-facility.c         |  2 +
>>  hw/s390x/meson.build              |  1 +
>>  hw/s390x/s390-virtio-ccw.c        | 14 +++++
>>  hw/s390x/sclpcpi.c                | 92 
>> +++++++++++++++++++++++++++++++
>>  include/hw/s390x/event-facility.h | 13 +++++
>>  5 files changed, 122 insertions(+)
>>  create mode 100644 hw/s390x/sclpcpi.c
> 
> [...]
> 
> 
>>  static void s390_cpu_plug(HotplugHandler *hotplug_dev,
>> diff --git a/hw/s390x/sclpcpi.c b/hw/s390x/sclpcpi.c
>> new file mode 100644
>> index 0000000000..13589459b1
>> --- /dev/null
>> +++ b/hw/s390x/sclpcpi.c
> 
> [...]
> 
>> +static void cpi_class_init(ObjectClass *klass, void *data)
> 
> Should be 'const void *data'.
> 

Ok, thank you.

>> +{
>> +    DeviceClass *dc = DEVICE_CLASS(klass);
>> +    SCLPEventClass *k = SCLP_EVENT_CLASS(klass);
>> +
>> +    dc->user_creatable = false;
>> +
>> +    k->can_handle_event = can_handle_event;
>> +    k->get_send_mask = send_mask;
>> +    k->get_receive_mask = receive_mask;
>> +    k->write_event_data = write_event_data;
>> +}
> 
> [...]

-- 
Mit freundlichen Grüßen / Kind regards
Shalini Chellathurai Saroja
Software Developer
Linux on IBM Z & KVM Development
IBM Deutschland Research & Development GmbH
Dept 1419, Schoenaicher Str. 220, 71032 Boeblingen
Vorsitzender des Aufsichtsrats: Wolfgang Wendt
Geschäftsführung: David Faller
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht 
Stuttgart, HRB 243294

[PATCH v4 2/4] hw/s390x: add Control-Program Identification to QOM

[Shalini Chellathurai Saroja]

Add Control-Program Identification data to the QEMU Object
Model (QOM), along with the timestamp in which the data was received.

Example:
virsh # qemu-monitor-command vm --pretty '{
"execute": "qom-get",
"arguments": {
"path": "/machine/sclp/s390-sclp-event-facility/sclpcpi",
"property": "control-program-id" }}'
{
  "return": {
    "timestamp": 1742390410685762000,
    "system-level": 74872343805430528,
    "sysplex-name": "PLEX ",
    "system-name": "TESTVM  ",
    "system-type": "LINUX   "
  },
  "id": "libvirt-15"
}

Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
---
 hw/s390x/sclpcpi.c                | 39 +++++++++++++++++++++
 include/hw/s390x/event-facility.h |  9 +++++
 qapi/machine.json                 | 58 +++++++++++++++++++++++++++++++
 3 files changed, 106 insertions(+)

diff --git a/hw/s390x/sclpcpi.c b/hw/s390x/sclpcpi.c
index 13589459b1..dcc8bd3245 100644
--- a/hw/s390x/sclpcpi.c
+++ b/hw/s390x/sclpcpi.c
@@ -18,7 +18,10 @@
   */
 
 #include "qemu/osdep.h"
+#include "qemu/timer.h"
 #include "hw/s390x/event-facility.h"
+#include "hw/s390x/ebcdic.h"
+#include "qapi/qapi-visit-machine.h"
 
 typedef struct Data {
     uint8_t id_format;
@@ -58,11 +61,39 @@ static int write_event_data(SCLPEvent *event, EventBufferHeader *evt_buf_hdr)
 {
     ControlProgramIdMsg *cpim = container_of(evt_buf_hdr, ControlProgramIdMsg,
                                              ebh);
+    SCLPEventCPI *e = SCLP_EVENT_CPI(event);
+
+    ascii_put(e->cpi.system_type, (char *)cpim->data.system_type, 8);
+    ascii_put(e->cpi.system_name, (char *)cpim->data.system_name, 8);
+    ascii_put(e->cpi.sysplex_name, (char *)cpim->data.sysplex_name, 8);
+    e->cpi.system_level = ldq_be_p(&cpim->data.system_level);
+    e->cpi.timestamp = qemu_clock_get_ns(QEMU_CLOCK_HOST);
 
     cpim->ebh.flags = SCLP_EVENT_BUFFER_ACCEPTED;
     return SCLP_RC_NORMAL_COMPLETION;
 }
 
+static void get_control_program_id(Object *obj, Visitor *v,
+                                   const char *name, void *opaque,
+                                   Error **errp)
+{
+    SCLPEventCPI *e = SCLP_EVENT_CPI(obj);
+    S390ControlProgramId *cpi;
+
+    cpi = &(S390ControlProgramId){
+        .system_type = g_strndup((char *) e->cpi.system_type,
+                                 sizeof(e->cpi.system_type)),
+        .system_name = g_strndup((char *) e->cpi.system_name,
+                                 sizeof(e->cpi.system_name)),
+        .system_level = e->cpi.system_level,
+        .sysplex_name = g_strndup((char *) e->cpi.sysplex_name,
+                                  sizeof(e->cpi.sysplex_name)),
+        .timestamp = e->cpi.timestamp
+    };
+
+    visit_type_S390ControlProgramId(v, name, &cpi, errp);
+}
+
 static void cpi_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
@@ -74,6 +105,14 @@ static void cpi_class_init(ObjectClass *klass, void *data)
     k->get_send_mask = send_mask;
     k->get_receive_mask = receive_mask;
     k->write_event_data = write_event_data;
+
+    object_class_property_add(klass, "control-program-id",
+                              "S390ControlProgramId",
+                              get_control_program_id,
+                              NULL, NULL, NULL);
+    object_class_property_set_description(klass, "control-program-id",
+        "Control-program identifiers provide data about the guest "
+        "operating system");
 }
 
 static const TypeInfo sclp_cpi_info = {
diff --git a/include/hw/s390x/event-facility.h b/include/hw/s390x/event-facility.h
index ef469e62ae..123c4ac49c 100644
--- a/include/hw/s390x/event-facility.h
+++ b/include/hw/s390x/event-facility.h
@@ -199,9 +199,18 @@ typedef struct SCLPEventCPI SCLPEventCPI;
 OBJECT_DECLARE_TYPE(SCLPEventCPI, SCLPEventCPIClass,
                     SCLP_EVENT_CPI)
 
+typedef struct ControlProgramId {
+    uint8_t system_type[8];
+    uint8_t system_name[8];
+    uint64_t system_level;
+    uint8_t sysplex_name[8];
+    uint64_t timestamp;
+} ControlProgramId;
+
 struct SCLPEventCPI {
     DeviceState qdev;
     SCLPEvent event;
+    ControlProgramId cpi;
 };
 
 #define TYPE_SCLP_EVENT_FACILITY "s390-sclp-event-facility"
diff --git a/qapi/machine.json b/qapi/machine.json
index a6b8795b09..cd2bcd2d13 100644
--- a/qapi/machine.json
+++ b/qapi/machine.json
@@ -1898,3 +1898,61 @@
 { 'command': 'x-query-interrupt-controllers',
   'returns': 'HumanReadableText',
   'features': [ 'unstable' ]}
+
+##
+# @S390ControlProgramId:
+#
+# Control-program identifiers provide data about the guest operating system.
+# The control-program identifiers are: system type, system name, system level
+# and sysplex name.
+#
+# In Linux, all the control-program identifiers are user configurable. The
+# system type, system name, and sysplex name use EBCDIC characters from
+# this set: capital A-Z, 0-9, $, @, #, and blank.  In Linux, the system type,
+# system name and sysplex name are arbitrary free-form texts.
+#
+# In Linux, the 8-byte hexadecimal system-level has the format
+# 0x<a><b><cc><dd><eeee><ff><gg><hh>, where:
+# <a>: is one hexadecimal byte, its most significant bit indicates hypervisor
+# use
+# <b>: is one digit that represents Linux distributions as follows
+# 0: generic Linux
+# 1: Red Hat Enterprise Linux
+# 2: SUSE Linux Enterprise Server
+# 3: Canonical Ubuntu
+# 4: Fedora
+# 5: openSUSE Leap
+# 6: Debian GNU/Linux
+# 7: Red Hat Enterprise Linux CoreOS
+# <cc>: are two digits for a distribution-specific encoding of the major version
+# of the distribution
+# <dd>: are two digits for a distribution-specific encoding of the minor version
+# of the distribution
+# <eeee>: are four digits for the patch level of the distribution
+# <ff>: are two digits for the major version of the kernel
+# <gg>: are two digits for the minor version of the kernel
+# <hh>: are two digits for the stable version of the kernel
+# (e.g. 74872343805430528, when converted to hex is 0x010a000000060b00). On
+# machines prior to z16, some of the values are not available to display.
+#
+# Sysplex refers to a cluster of logical partitions that communicates and
+# co-operates with each other.
+#
+# @system-type: operating system (e.g. "LINUX   ")
+#
+# @system-name: user configurable name of the VM (e.g. "TESTVM  ")
+#
+# @system-level: distribution and kernel version in Linux
+#
+# @sysplex-name: sysplex which the VM belongs to, if any (e.g. "PLEX ")
+#
+# @timestamp: latest update of CPI data in nanoseconds since the UNIX EPOCH
+#
+# Since: 10.0
+##
+{ 'struct': 'S390ControlProgramId', 'data': {
+     'system-type': 'str',
+     'system-name': 'str',
+     'system-level': 'uint64',
+     'sysplex-name': 'str',
+     'timestamp': 'uint64' } }
-- 
2.49.0

Re: [PATCH v4 2/4] hw/s390x: add Control-Program Identification to QOM

[Nina Schoetterl-Glausch]

On Thu, 2025-04-10 at 17:09 +0200, Shalini Chellathurai Saroja wrote:
> Add Control-Program Identification data to the QEMU Object
> Model (QOM), along with the timestamp in which the data was received.
> 
> Example:
> virsh # qemu-monitor-command vm --pretty '{
> "execute": "qom-get",
> "arguments": {
> "path": "/machine/sclp/s390-sclp-event-facility/sclpcpi",
> "property": "control-program-id" }}'
> {
>   "return": {
>     "timestamp": 1742390410685762000,
>     "system-level": 74872343805430528,
>     "sysplex-name": "PLEX ",
>     "system-name": "TESTVM  ",
>     "system-type": "LINUX   "
>   },
>   "id": "libvirt-15"
> }
> 
> Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
> ---
>  hw/s390x/sclpcpi.c                | 39 +++++++++++++++++++++
>  include/hw/s390x/event-facility.h |  9 +++++
>  qapi/machine.json                 | 58 +++++++++++++++++++++++++++++++
>  3 files changed, 106 insertions(+)

[...]

> --- a/include/hw/s390x/event-facility.h
> +++ b/include/hw/s390x/event-facility.h
> @@ -199,9 +199,18 @@ typedef struct SCLPEventCPI SCLPEventCPI;
>  OBJECT_DECLARE_TYPE(SCLPEventCPI, SCLPEventCPIClass,
>                      SCLP_EVENT_CPI)
>  
> +typedef struct ControlProgramId {
> +    uint8_t system_type[8];
> +    uint8_t system_name[8];
> +    uint64_t system_level;
> +    uint8_t sysplex_name[8];
> +    uint64_t timestamp;
> +} ControlProgramId;
> +
>  struct SCLPEventCPI {
>      DeviceState qdev;
>      SCLPEvent event;
> +    ControlProgramId cpi;

Now that this struct exists I would go ahead and inline ControlProgramId.

>  };
>  
>  #define TYPE_SCLP_EVENT_FACILITY "s390-sclp-event-facility"

[...]
-- 
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Wolfgang Wendt
Geschäftsführung: David Faller
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294

Re: [PATCH v4 2/4] hw/s390x: add Control-Program Identification to QOM

[Shalini Chellathurai Saroja]

On 2025-04-28 14:01, Nina Schoetterl-Glausch wrote:
> On Thu, 2025-04-10 at 17:09 +0200, Shalini Chellathurai Saroja wrote:
>> Add Control-Program Identification data to the QEMU Object
>> Model (QOM), along with the timestamp in which the data was received.
>> 
>> Example:
>> virsh # qemu-monitor-command vm --pretty '{
>> "execute": "qom-get",
>> "arguments": {
>> "path": "/machine/sclp/s390-sclp-event-facility/sclpcpi",
>> "property": "control-program-id" }}'
>> {
>>   "return": {
>>     "timestamp": 1742390410685762000,
>>     "system-level": 74872343805430528,
>>     "sysplex-name": "PLEX ",
>>     "system-name": "TESTVM  ",
>>     "system-type": "LINUX   "
>>   },
>>   "id": "libvirt-15"
>> }
>> 
>> Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
>> ---
>>  hw/s390x/sclpcpi.c                | 39 +++++++++++++++++++++
>>  include/hw/s390x/event-facility.h |  9 +++++
>>  qapi/machine.json                 | 58 
>> +++++++++++++++++++++++++++++++
>>  3 files changed, 106 insertions(+)
> 
> [...]
> 
>> --- a/include/hw/s390x/event-facility.h
>> +++ b/include/hw/s390x/event-facility.h
>> @@ -199,9 +199,18 @@ typedef struct SCLPEventCPI SCLPEventCPI;
>>  OBJECT_DECLARE_TYPE(SCLPEventCPI, SCLPEventCPIClass,
>>                      SCLP_EVENT_CPI)
>> 
>> +typedef struct ControlProgramId {
>> +    uint8_t system_type[8];
>> +    uint8_t system_name[8];
>> +    uint64_t system_level;
>> +    uint8_t sysplex_name[8];
>> +    uint64_t timestamp;
>> +} ControlProgramId;
>> +
>>  struct SCLPEventCPI {
>>      DeviceState qdev;
>>      SCLPEvent event;
>> +    ControlProgramId cpi;
> 
> Now that this struct exists I would go ahead and inline 
> ControlProgramId.

Ok, I will do so, thank you.
> 
>>  };
>> 
>>  #define TYPE_SCLP_EVENT_FACILITY "s390-sclp-event-facility"
> 
> [...]

-- 
Mit freundlichen Grüßen / Kind regards
Shalini Chellathurai Saroja
Software Developer
Linux on IBM Z & KVM Development
IBM Deutschland Research & Development GmbH
Dept 1419, Schoenaicher Str. 220, 71032 Boeblingen
Vorsitzender des Aufsichtsrats: Wolfgang Wendt
Geschäftsführung: David Faller
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht 
Stuttgart, HRB 243294

Re: [PATCH v4 2/4] hw/s390x: add Control-Program Identification to QOM

[Thomas Huth]

On 10/04/2025 17.09, Shalini Chellathurai Saroja wrote:
> Add Control-Program Identification data to the QEMU Object
> Model (QOM), along with the timestamp in which the data was received.
...
> diff --git a/hw/s390x/sclpcpi.c b/hw/s390x/sclpcpi.c
> index 13589459b1..dcc8bd3245 100644
> --- a/hw/s390x/sclpcpi.c
> +++ b/hw/s390x/sclpcpi.c
> @@ -18,7 +18,10 @@
>     */
>   
>   #include "qemu/osdep.h"
> +#include "qemu/timer.h"
>   #include "hw/s390x/event-facility.h"
> +#include "hw/s390x/ebcdic.h"
> +#include "qapi/qapi-visit-machine.h"
>   
>   typedef struct Data {
>       uint8_t id_format;
> @@ -58,11 +61,39 @@ static int write_event_data(SCLPEvent *event, EventBufferHeader *evt_buf_hdr)
>   {
>       ControlProgramIdMsg *cpim = container_of(evt_buf_hdr, ControlProgramIdMsg,
>                                                ebh);
> +    SCLPEventCPI *e = SCLP_EVENT_CPI(event);
> +
> +    ascii_put(e->cpi.system_type, (char *)cpim->data.system_type, 8);
> +    ascii_put(e->cpi.system_name, (char *)cpim->data.system_name, 8);
> +    ascii_put(e->cpi.sysplex_name, (char *)cpim->data.sysplex_name, 8);

Would it be possible to use sizeof() instead of hard-coding "8" here?

  Thanks,
   Thomas

Re: [PATCH v4 2/4] hw/s390x: add Control-Program Identification to QOM

[Shalini Chellathurai Saroja]

On 2025-04-30 12:34, Thomas Huth wrote:
> On 10/04/2025 17.09, Shalini Chellathurai Saroja wrote:
>> Add Control-Program Identification data to the QEMU Object
>> Model (QOM), along with the timestamp in which the data was received.
> ...
>> diff --git a/hw/s390x/sclpcpi.c b/hw/s390x/sclpcpi.c
>> index 13589459b1..dcc8bd3245 100644
>> --- a/hw/s390x/sclpcpi.c
>> +++ b/hw/s390x/sclpcpi.c
>> @@ -18,7 +18,10 @@
>>     */
>>     #include "qemu/osdep.h"
>> +#include "qemu/timer.h"
>>   #include "hw/s390x/event-facility.h"
>> +#include "hw/s390x/ebcdic.h"
>> +#include "qapi/qapi-visit-machine.h"
>>     typedef struct Data {
>>       uint8_t id_format;
>> @@ -58,11 +61,39 @@ static int write_event_data(SCLPEvent *event, 
>> EventBufferHeader *evt_buf_hdr)
>>   {
>>       ControlProgramIdMsg *cpim = container_of(evt_buf_hdr, 
>> ControlProgramIdMsg,
>>                                                ebh);
>> +    SCLPEventCPI *e = SCLP_EVENT_CPI(event);
>> +
>> +    ascii_put(e->cpi.system_type, (char *)cpim->data.system_type, 8);
>> +    ascii_put(e->cpi.system_name, (char *)cpim->data.system_name, 8);
>> +    ascii_put(e->cpi.sysplex_name, (char *)cpim->data.sysplex_name, 
>> 8);
> 
> Would it be possible to use sizeof() instead of hard-coding "8" here?

Hello Thomas,

Yes, it is. I will do so. Thank you very much for the review.

I will also move the property use_cpi to ccw_machine_10_0_class_options, 
as version 10.0 is already released.

> 
>  Thanks,
>   Thomas

-- 
Mit freundlichen Grüßen / Kind regards
Shalini Chellathurai Saroja
Software Developer
Linux on IBM Z & KVM Development
IBM Deutschland Research & Development GmbH
Dept 1419, Schoenaicher Str. 220, 71032 Boeblingen
Vorsitzender des Aufsichtsrats: Wolfgang Wendt
Geschäftsführung: David Faller
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht 
Stuttgart, HRB 243294

[PATCH v4 3/4] hw/s390x: support migration of CPI data

[Shalini Chellathurai Saroja]

Register Control-Program Identification data with the live
migration infrastructure.

Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
Reviewed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
---
 hw/s390x/sclpcpi.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/hw/s390x/sclpcpi.c b/hw/s390x/sclpcpi.c
index dcc8bd3245..40a74c16b5 100644
--- a/hw/s390x/sclpcpi.c
+++ b/hw/s390x/sclpcpi.c
@@ -22,6 +22,7 @@
 #include "hw/s390x/event-facility.h"
 #include "hw/s390x/ebcdic.h"
 #include "qapi/qapi-visit-machine.h"
+#include "migration/vmstate.h"
 
 typedef struct Data {
     uint8_t id_format;
@@ -94,12 +95,36 @@ static void get_control_program_id(Object *obj, Visitor *v,
     visit_type_S390ControlProgramId(v, name, &cpi, errp);
 }
 
+static const VMStateDescription vmstate_control_program_id = {
+    .name = "s390_control_program_id",
+    .version_id = 0,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT8_ARRAY(system_type, ControlProgramId, 8),
+        VMSTATE_UINT8_ARRAY(system_name, ControlProgramId, 8),
+        VMSTATE_UINT64(system_level, ControlProgramId),
+        VMSTATE_UINT8_ARRAY(sysplex_name, ControlProgramId, 8),
+        VMSTATE_UINT64(timestamp, ControlProgramId),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static const VMStateDescription vmstate_sclpcpi = {
+    .name = "s390_sclpcpi",
+    .version_id = 0,
+    .fields = (const VMStateField[]) {
+        VMSTATE_STRUCT(cpi, SCLPEventCPI, 0, vmstate_control_program_id,
+                       ControlProgramId),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static void cpi_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
     SCLPEventClass *k = SCLP_EVENT_CLASS(klass);
 
     dc->user_creatable = false;
+    dc->vmsd =  &vmstate_sclpcpi;
 
     k->can_handle_event = can_handle_event;
     k->get_send_mask = send_mask;
-- 
2.49.0

[PATCH v4 4/4] hw/s390x: compat handling for backward migration

[Shalini Chellathurai Saroja]

Add Control-Program Identification (CPI) device to QOM only when the virtual
machine supports CPI. CPI is supported from "s390-ccw-virtio-10.0" machine
and higher.

Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
---
 hw/s390x/s390-virtio-ccw.c         | 10 +++++++++-
 include/hw/s390x/s390-virtio-ccw.h |  1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 7f28cbd1de..81832ee638 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -274,6 +274,7 @@ static void s390_create_sclpcpi(SCLPDevice *sclp)
 static void ccw_init(MachineState *machine)
 {
     MachineClass *mc = MACHINE_GET_CLASS(machine);
+    S390CcwMachineClass *s390mc = S390_CCW_MACHINE_CLASS(mc);
     S390CcwMachineState *ms = S390_CCW_MACHINE(machine);
     int ret;
     VirtualCssBus *css_bus;
@@ -336,7 +337,10 @@ static void ccw_init(MachineState *machine)
     s390_init_tod();
 
     /* init SCLP event Control-Program Identification */
-    s390_create_sclpcpi(ms->sclp);
+    if (s390mc->use_cpi) {
+        s390_create_sclpcpi(ms->sclp);
+    }
+
 }
 
 static void s390_cpu_plug(HotplugHandler *hotplug_dev,
@@ -827,6 +831,7 @@ static void ccw_machine_class_init(ObjectClass *oc, void *data)
 
     s390mc->hpage_1m_allowed = true;
     s390mc->max_threads = 1;
+    s390mc->use_cpi = true;
     mc->reset = s390_machine_reset;
     mc->block_default_type = IF_VIRTIO;
     mc->no_cdrom = 1;
@@ -955,6 +960,9 @@ static void ccw_machine_9_2_class_options(MachineClass *mc)
         { TYPE_S390_PCI_DEVICE, "relaxed-translation", "off", },
     };
 
+    S390CcwMachineClass *s390mc = S390_CCW_MACHINE_CLASS(mc);
+    s390mc->use_cpi = false;
+
     ccw_machine_10_0_class_options(mc);
     compat_props_add(mc->compat_props, hw_compat_9_2, hw_compat_9_2_len);
     compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat));
diff --git a/include/hw/s390x/s390-virtio-ccw.h b/include/hw/s390x/s390-virtio-ccw.h
index 686d9497d2..fc4112fbf5 100644
--- a/include/hw/s390x/s390-virtio-ccw.h
+++ b/include/hw/s390x/s390-virtio-ccw.h
@@ -55,6 +55,7 @@ struct S390CcwMachineClass {
     /*< public >*/
     bool hpage_1m_allowed;
     int max_threads;
+    bool use_cpi;
 };
 
 /* 1M huge page mappings allowed by the machine */
-- 
2.49.0

Re: [PATCH v4 4/4] hw/s390x: compat handling for backward migration

[Nina Schoetterl-Glausch]

On Thu, 2025-04-10 at 17:09 +0200, Shalini Chellathurai Saroja wrote:
> Add Control-Program Identification (CPI) device to QOM only when the virtual
> machine supports CPI. CPI is supported from "s390-ccw-virtio-10.0" machine
> and higher.
> 
> Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
> ---
>  hw/s390x/s390-virtio-ccw.c         | 10 +++++++++-
>  include/hw/s390x/s390-virtio-ccw.h |  1 +
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index 7f28cbd1de..81832ee638 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -274,6 +274,7 @@ static void s390_create_sclpcpi(SCLPDevice *sclp)
>  static void ccw_init(MachineState *machine)
>  {
>      MachineClass *mc = MACHINE_GET_CLASS(machine);
> +    S390CcwMachineClass *s390mc = S390_CCW_MACHINE_CLASS(mc);
>      S390CcwMachineState *ms = S390_CCW_MACHINE(machine);
>      int ret;
>      VirtualCssBus *css_bus;
> @@ -336,7 +337,10 @@ static void ccw_init(MachineState *machine)
>      s390_init_tod();
>  
>      /* init SCLP event Control-Program Identification */
> -    s390_create_sclpcpi(ms->sclp);
> +    if (s390mc->use_cpi) {
> +        s390_create_sclpcpi(ms->sclp);
> +    }

Fixing this in a separate commit could be bad for bisecting.
You introduce use_cpi in an earlier commit set to false and
then flipping it in the migration patch for new machines.
This way there is no broken intermediate state.

I would also squash the compat migration changes into the previous
patch.

>  }
>  
>  static void s390_cpu_plug(HotplugHandler *hotplug_dev,
> @@ -827,6 +831,7 @@ static void ccw_machine_class_init(ObjectClass *oc, void *data)
>  
>      s390mc->hpage_1m_allowed = true;
>      s390mc->max_threads = 1;
> +    s390mc->use_cpi = true;
>      mc->reset = s390_machine_reset;
>      mc->block_default_type = IF_VIRTIO;
>      mc->no_cdrom = 1;
> @@ -955,6 +960,9 @@ static void ccw_machine_9_2_class_options(MachineClass *mc)
>          { TYPE_S390_PCI_DEVICE, "relaxed-translation", "off", },
>      };
>  
> +    S390CcwMachineClass *s390mc = S390_CCW_MACHINE_CLASS(mc);
> +    s390mc->use_cpi = false;
> +
>      ccw_machine_10_0_class_options(mc);
>      compat_props_add(mc->compat_props, hw_compat_9_2, hw_compat_9_2_len);
>      compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat));
> diff --git a/include/hw/s390x/s390-virtio-ccw.h b/include/hw/s390x/s390-virtio-ccw.h
> index 686d9497d2..fc4112fbf5 100644
> --- a/include/hw/s390x/s390-virtio-ccw.h
> +++ b/include/hw/s390x/s390-virtio-ccw.h
> @@ -55,6 +55,7 @@ struct S390CcwMachineClass {
>      /*< public >*/
>      bool hpage_1m_allowed;
>      int max_threads;
> +    bool use_cpi;
>  };
>  
>  /* 1M huge page mappings allowed by the machine */

-- 
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Wolfgang Wendt
Geschäftsführung: David Faller
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294

Re: [PATCH v4 4/4] hw/s390x: compat handling for backward migration

[Shalini Chellathurai Saroja]

On 2025-04-28 14:05, Nina Schoetterl-Glausch wrote:
> On Thu, 2025-04-10 at 17:09 +0200, Shalini Chellathurai Saroja wrote:
>> Add Control-Program Identification (CPI) device to QOM only when the 
>> virtual
>> machine supports CPI. CPI is supported from "s390-ccw-virtio-10.0" 
>> machine
>> and higher.
>> 
>> Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
>> ---
>>  hw/s390x/s390-virtio-ccw.c         | 10 +++++++++-
>>  include/hw/s390x/s390-virtio-ccw.h |  1 +
>>  2 files changed, 10 insertions(+), 1 deletion(-)
>> 
>> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
>> index 7f28cbd1de..81832ee638 100644
>> --- a/hw/s390x/s390-virtio-ccw.c
>> +++ b/hw/s390x/s390-virtio-ccw.c
>> @@ -274,6 +274,7 @@ static void s390_create_sclpcpi(SCLPDevice *sclp)
>>  static void ccw_init(MachineState *machine)
>>  {
>>      MachineClass *mc = MACHINE_GET_CLASS(machine);
>> +    S390CcwMachineClass *s390mc = S390_CCW_MACHINE_CLASS(mc);
>>      S390CcwMachineState *ms = S390_CCW_MACHINE(machine);
>>      int ret;
>>      VirtualCssBus *css_bus;
>> @@ -336,7 +337,10 @@ static void ccw_init(MachineState *machine)
>>      s390_init_tod();
>> 
>>      /* init SCLP event Control-Program Identification */
>> -    s390_create_sclpcpi(ms->sclp);
>> +    if (s390mc->use_cpi) {
>> +        s390_create_sclpcpi(ms->sclp);
>> +    }
> 
> Fixing this in a separate commit could be bad for bisecting.

Ok.

> You introduce use_cpi in an earlier commit set to false and
> then flipping it in the migration patch for new machines.
> This way there is no broken intermediate state.
> 
> I would also squash the compat migration changes into the previous
> patch.
> 

Hello Nina,

If use_cpi is set to false in patch 1, then the sclpcpi device will not 
be instantiated even for new machines at that point. The sclpcpi device 
will only be instantiated when the use_cpi is set to true in the 
migration patch.

I prefer to squash this entire patch to patch 1, then the sclpcpi device 
will only be instantiated for new machines with the code in patch 1 
itself and will not be dependent on the migration patch. I like this 
approach as the logic to add sclpcpi device is complete in patch 1.

What do you think?, thank you.

>>  }
>> 
>>  static void s390_cpu_plug(HotplugHandler *hotplug_dev,
>> @@ -827,6 +831,7 @@ static void ccw_machine_class_init(ObjectClass 
>> *oc, void *data)
>> 
>>      s390mc->hpage_1m_allowed = true;
>>      s390mc->max_threads = 1;
>> +    s390mc->use_cpi = true;
>>      mc->reset = s390_machine_reset;
>>      mc->block_default_type = IF_VIRTIO;
>>      mc->no_cdrom = 1;
>> @@ -955,6 +960,9 @@ static void 
>> ccw_machine_9_2_class_options(MachineClass *mc)
>>          { TYPE_S390_PCI_DEVICE, "relaxed-translation", "off", },
>>      };
>> 
>> +    S390CcwMachineClass *s390mc = S390_CCW_MACHINE_CLASS(mc);
>> +    s390mc->use_cpi = false;
>> +
>>      ccw_machine_10_0_class_options(mc);
>>      compat_props_add(mc->compat_props, hw_compat_9_2, 
>> hw_compat_9_2_len);
>>      compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat));
>> diff --git a/include/hw/s390x/s390-virtio-ccw.h 
>> b/include/hw/s390x/s390-virtio-ccw.h
>> index 686d9497d2..fc4112fbf5 100644
>> --- a/include/hw/s390x/s390-virtio-ccw.h
>> +++ b/include/hw/s390x/s390-virtio-ccw.h
>> @@ -55,6 +55,7 @@ struct S390CcwMachineClass {
>>      /*< public >*/
>>      bool hpage_1m_allowed;
>>      int max_threads;
>> +    bool use_cpi;
>>  };
>> 
>>  /* 1M huge page mappings allowed by the machine */

-- 
Mit freundlichen Grüßen / Kind regards
Shalini Chellathurai Saroja
Software Developer
Linux on IBM Z & KVM Development
IBM Deutschland Research & Development GmbH
Dept 1419, Schoenaicher Str. 220, 71032 Boeblingen
Vorsitzender des Aufsichtsrats: Wolfgang Wendt
Geschäftsführung: David Faller
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht 
Stuttgart, HRB 243294

Re: [PATCH v4 4/4] hw/s390x: compat handling for backward migration

[Nina Schoetterl-Glausch]

On Mon, 2025-05-05 at 10:54 +0200, Shalini Chellathurai Saroja wrote:
> On 2025-04-28 14:05, Nina Schoetterl-Glausch wrote:
> > On Thu, 2025-04-10 at 17:09 +0200, Shalini Chellathurai Saroja wrote:
> > > Add Control-Program Identification (CPI) device to QOM only when the 
> > > virtual
> > > machine supports CPI. CPI is supported from "s390-ccw-virtio-10.0" 
> > > machine
> > > and higher.
> > > 
> > > Signed-off-by: Shalini Chellathurai Saroja <shalini@linux.ibm.com>
> > > ---
> > >  hw/s390x/s390-virtio-ccw.c         | 10 +++++++++-
> > >  include/hw/s390x/s390-virtio-ccw.h |  1 +
> > >  2 files changed, 10 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> > > index 7f28cbd1de..81832ee638 100644
> > > --- a/hw/s390x/s390-virtio-ccw.c
> > > +++ b/hw/s390x/s390-virtio-ccw.c

[...]

> > Fixing this in a separate commit could be bad for bisecting.
> 
> Ok.
> 
> > You introduce use_cpi in an earlier commit set to false and
> > then flipping it in the migration patch for new machines.
> > This way there is no broken intermediate state.
> > 
> > I would also squash the compat migration changes into the previous
> > patch.
> > 
> 
> Hello Nina,
> 
> If use_cpi is set to false in patch 1, then the sclpcpi device will not 
> be instantiated even for new machines at that point. The sclpcpi device 
> will only be instantiated when the use_cpi is set to true in the 
> migration patch.
> 
> I prefer to squash this entire patch to patch 1, then the sclpcpi device 
> will only be instantiated for new machines with the code in patch 1 
> itself and will not be dependent on the migration patch. I like this 
> approach as the logic to add sclpcpi device is complete in patch 1.
> 
> What do you think?, thank you.

Sounds good!

[...]


-- 
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Wolfgang Wendt
Geschäftsführung: David Faller
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294