[RFC PATCH v2 0/5] Report vfio-ap configuration changes

[RFC PATCH v2 0/5] Report vfio-ap configuration changes

[Rorie Reyes]

Changelog:

v2:
- removed warnings that weren't needed
- added unregister function
- removed whitelines
- changed variable names for consistency
- removed rc variable and returning 1 or 0 outright
- reversed logics for if statements
- using g_free() instead of free()
- replaced hardcoded numeric values by defining them with #define
in the header 

--------------------------------------------------------------------------
This patch series creates and registers a handler that is called when
userspace is notified by the kernel that a guest's AP configuration has
changed. The handler in turn notifies the guest that its AP configuration
has changed. This allows the guest to immediately respond to AP
configuration changes rather than relying on polling or some other
inefficient mechanism for detecting config changes.

Rorie Reyes (5):
  linux-headers: NOTFORMERGE - placeholder uapi updates for AP config
    change
  hw/vfio/ap: notification handler for AP config changed event
  hw/vfio/ap: store object indicating AP config changed in a queue
  hw/vfio/ap: Storing event information for an AP configuration change
    event
  s390: implementing CHSC SEI for AP config change

 hw/vfio/ap.c                 | 79 ++++++++++++++++++++++++++++++++++++
 include/hw/s390x/ap-bridge.h | 22 ++++++++++
 linux-headers/linux/vfio.h   |  1 +
 target/s390x/ioinst.c        | 11 ++++-
 4 files changed, 111 insertions(+), 2 deletions(-)

-- 
2.39.5 (Apple Git-154)

[RFC PATCH v2 1/5] linux-headers: NOTFORMERGE - placeholder uapi updates for AP config change

[Rorie Reyes]

This patch adds enumeration constant VFIO_AP_CFG_CHG_IRQ_INDEX to specify
an IRQ index for signaling that a change has been made to the guest's AP
configuration. This is a placeholder for QEMU patches that use this value
since it is a linux-headers update which includes changes that aren't
merged into the kernel. Linux-headers patches should be generated using
scripts/update-linux-headers.sh.

Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
---
 linux-headers/linux/vfio.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
index 1b5e254d6a..d0426b5ec0 100644
--- a/linux-headers/linux/vfio.h
+++ b/linux-headers/linux/vfio.h
@@ -671,6 +671,7 @@ enum {
  */
 enum {
 	VFIO_AP_REQ_IRQ_INDEX,
+	VFIO_AP_CFG_CHG_IRQ_INDEX,
 	VFIO_AP_NUM_IRQS
 };
 
-- 
2.39.5 (Apple Git-154)

Re: [RFC PATCH v2 1/5] linux-headers: NOTFORMERGE - placeholder uapi updates for AP config change

[Cédric Le Goater]

Hello Rorie,

On 2/4/25 18:07, Rorie Reyes wrote:
> This patch adds enumeration constant VFIO_AP_CFG_CHG_IRQ_INDEX to specify
> an IRQ index for signaling that a change has been made to the guest's AP
> configuration. This is a placeholder for QEMU patches that use this value
> since it is a linux-headers update which includes changes that aren't
> merged into the kernel. Linux-headers patches should be generated using
> scripts/update-linux-headers.sh.
> 
> Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
> ---
>   linux-headers/linux/vfio.h | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
> index 1b5e254d6a..d0426b5ec0 100644
> --- a/linux-headers/linux/vfio.h
> +++ b/linux-headers/linux/vfio.h
> @@ -671,6 +671,7 @@ enum {
>    */
>   enum {
>   	VFIO_AP_REQ_IRQ_INDEX,
> +	VFIO_AP_CFG_CHG_IRQ_INDEX,
>   	VFIO_AP_NUM_IRQS
>   };
>   

Are the kernel changes planned for 6.14 ?

FYI, QEMU 10.0 hard freeze is scheduled for 2025-03-18 which is
approximately when 6.14-rc7 will be released.

Thanks,

C.

Re: [RFC PATCH v2 1/5] linux-headers: NOTFORMERGE - placeholder uapi updates for AP config change

[Rorie Reyes]

On 2/5/25 3:38 AM, Cédric Le Goater wrote:

>
> Are the kernel changes planned for 6.14 ?
>
> FYI, QEMU 10.0 hard freeze is scheduled for 2025-03-18 which is
> approximately when 6.14-rc7 will be released.
>
> Thanks,
>
> C. 

Vasily - Since you applied my kernel patches already ([RFC PATCH v2] 
s390/vfio-ap: Notify userspace that guest's AP config changed when mdev 
removed), would you be able to answer Cedric's

a question?

Cedric - I have some changes I need to make based on Tony's review 
comments from Friday, but I'll wait to post it once you get an answer 
for your question. Sorry I took a while to respond. I had to

make some changes for my kernel code this past month.

Re: [RFC PATCH v2 1/5] linux-headers: NOTFORMERGE - placeholder uapi updates for AP config change

[Cédric Le Goater]

Hello Rorie,



On 3/10/25 15:20, Rorie Reyes wrote:
> On 2/5/25 3:38 AM, Cédric Le Goater wrote:
> 
>>
>> Are the kernel changes planned for 6.14 ?
>>
>> FYI, QEMU 10.0 hard freeze is scheduled for 2025-03-18 which is
>> approximately when 6.14-rc7 will be released.
>>
>> Thanks,
>>
>> C. 
> 
> Vasily - Since you applied my kernel patches already ([RFC PATCH v2] s390/vfio-ap: Notify userspace that guest's AP config changed when mdev removed), would you be able to answer Cedric's
> 
> a question?
> 
> Cedric - I have some changes I need to make based on Tony's review comments from Friday, but I'll wait to post it once you get an answer for your question. Sorry I took a while to respond. I had to
> 
> make some changes for my kernel code this past month.
> 

AFAICT, the changes were merged in the s390 sub-maintainer tree,
07d89045bffea30ef08b902c2441a3329e44f29d, and they haven't reached
Linux master yet. Seems a bit late for the 6.14 cycle now.

linux-headers in QEMU are in sync with version 6.14-rc3 and that
should the last update before QEMU 10.0 soft-freeze tomorrow.

Most likely, this series should now target the next cycles:
Linux 6.15 and QEMU 10.1. We have time.


Thanks,

C.

Re: [RFC PATCH v2 1/5] linux-headers: NOTFORMERGE - placeholder uapi updates for AP config change

[Rorie Reyes]

On 3/10/25 10:38 AM, Cédric Le Goater wrote:
> Hello Rorie,
>
>
>
> On 3/10/25 15:20, Rorie Reyes wrote:
>> On 2/5/25 3:38 AM, Cédric Le Goater wrote:
>>
>>>
>>> Are the kernel changes planned for 6.14 ?
>>>
>>> FYI, QEMU 10.0 hard freeze is scheduled for 2025-03-18 which is
>>> approximately when 6.14-rc7 will be released.
>>>
>>> Thanks,
>>>
>>> C. 
>>
>> Vasily - Since you applied my kernel patches already ([RFC PATCH v2] 
>> s390/vfio-ap: Notify userspace that guest's AP config changed when 
>> mdev removed), would you be able to answer Cedric's
>>
>> a question?
>>
>> Cedric - I have some changes I need to make based on Tony's review 
>> comments from Friday, but I'll wait to post it once you get an answer 
>> for your question. Sorry I took a while to respond. I had to
>>
>> make some changes for my kernel code this past month.
>>
>
> AFAICT, the changes were merged in the s390 sub-maintainer tree,
> 07d89045bffea30ef08b902c2441a3329e44f29d, and they haven't reached
> Linux master yet. Seems a bit late for the 6.14 cycle now.
>
> linux-headers in QEMU are in sync with version 6.14-rc3 and that
> should the last update before QEMU 10.0 soft-freeze tomorrow.
>
> Most likely, this series should now target the next cycles:
> Linux 6.15 and QEMU 10.1. We have time.
>
>
> Thanks,
>
> C.
Thanks Cedric! I'll post the v3 patch from Tony's review

Re: [RFC PATCH v2 1/5] linux-headers: NOTFORMERGE - placeholder uapi updates for AP config change

[Vasily Gorbik]

On Mon, Mar 10, 2025 at 10:20:05AM -0400, Rorie Reyes wrote:
> On 2/5/25 3:38 AM, Cédric Le Goater wrote:
> 
> > 
> > Are the kernel changes planned for 6.14 ?
> >
> >
> > 
> > FYI, QEMU 10.0 hard freeze is scheduled for 2025-03-18 which is
> > approximately when 6.14-rc7 will be released.
> > 
> > Thanks,
> > 
> > C.
> 
> Vasily - Since you applied my kernel patches already ([RFC PATCH v2]
> s390/vfio-ap: Notify userspace that guest's AP config changed when mdev
> removed), would you be able to answer Cedric's

We are at v6.14-rc6. The changes are queued for the 6.15 merge window.

https://lore.kernel.org/r/20250107183645.90082-1-rreyes@linux.ibm.com
https://lore.kernel.org/r/20250304200812.54556-1-rreyes@linux.ibm.com

Re: [RFC PATCH v2 1/5] linux-headers: NOTFORMERGE - placeholder uapi updates for AP config change

[Rorie Reyes]

On 3/10/25 10:47 AM, Vasily Gorbik wrote:
> On Mon, Mar 10, 2025 at 10:20:05AM -0400, Rorie Reyes wrote:
>> On 2/5/25 3:38 AM, Cédric Le Goater wrote:
>>
>>> Are the kernel changes planned for 6.14 ?
>>>
>>>
>>>
>>> FYI, QEMU 10.0 hard freeze is scheduled for 2025-03-18 which is
>>> approximately when 6.14-rc7 will be released.
>>>
>>> Thanks,
>>>
>>> C.
>> Vasily - Since you applied my kernel patches already ([RFC PATCH v2]
>> s390/vfio-ap: Notify userspace that guest's AP config changed when mdev
>> removed), would you be able to answer Cedric's
> We are at v6.14-rc6. The changes are queued for the 6.15 merge window.
>
> https://lore.kernel.org/r/20250107183645.90082-1-rreyes@linux.ibm.com
> https://lore.kernel.org/r/20250304200812.54556-1-rreyes@linux.ibm.com
Thanks Vasily!

[RFC PATCH v2 2/5] hw/vfio/ap: notification handler for AP config changed event

[Rorie Reyes]

Register an event notifier handler to process AP configuration
change events by queuing the event and generating a CRW to let
the guest know its AP configuration has changed

Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
---
 hw/vfio/ap.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
index 30b08ad375..a2b3735349 100644
--- a/hw/vfio/ap.c
+++ b/hw/vfio/ap.c
@@ -18,6 +18,7 @@
 #include "hw/vfio/vfio-common.h"
 #include "system/iommufd.h"
 #include "hw/s390x/ap-device.h"
+#include "hw/s390x/css.h"
 #include "qemu/error-report.h"
 #include "qemu/event_notifier.h"
 #include "qemu/main-loop.h"
@@ -37,6 +38,7 @@ struct VFIOAPDevice {
     APDevice apdev;
     VFIODevice vdev;
     EventNotifier req_notifier;
+    EventNotifier cfg_notifier;
 };
 
 OBJECT_DECLARE_SIMPLE_TYPE(VFIOAPDevice, VFIO_AP_DEVICE)
@@ -70,6 +72,16 @@ static void vfio_ap_req_notifier_handler(void *opaque)
     }
 }
 
+static void vfio_ap_cfg_chg_notifier_handler(void *opaque)
+{
+    VFIOAPDevice *vapdev = opaque;
+
+    if (!event_notifier_test_and_clear(&vapdev->cfg_notifier)) {
+        css_generate_css_crws(0);
+    }
+
+}
+
 static bool vfio_ap_register_irq_notifier(VFIOAPDevice *vapdev,
                                           unsigned int irq, Error **errp)
 {
@@ -85,6 +97,10 @@ static bool vfio_ap_register_irq_notifier(VFIOAPDevice *vapdev,
         notifier = &vapdev->req_notifier;
         fd_read = vfio_ap_req_notifier_handler;
         break;
+    case VFIO_AP_CFG_CHG_IRQ_INDEX:
+        notifier = &vapdev->cfg_notifier;
+        fd_read = vfio_ap_cfg_chg_notifier_handler;
+        break;
     default:
         error_setg(errp, "vfio: Unsupported device irq(%d)", irq);
         return false;
@@ -136,6 +152,9 @@ static void vfio_ap_unregister_irq_notifier(VFIOAPDevice *vapdev,
     case VFIO_AP_REQ_IRQ_INDEX:
         notifier = &vapdev->req_notifier;
         break;
+    case VFIO_AP_CFG_CHG_IRQ_INDEX:
+        notifier = &vapdev->cfg_notifier;
+        break;
     default:
         error_report("vfio: Unsupported device irq(%d)", irq);
         return;
@@ -175,6 +194,15 @@ static void vfio_ap_realize(DeviceState *dev, Error **errp)
         warn_report_err(err);
     }
 
+    if (!vfio_ap_register_irq_notifier(vapdev, VFIO_AP_CFG_CHG_IRQ_INDEX, &err))
+    {
+        /*
+         * Report this error, but do not make it a failing condition.
+         * Lack of this IRQ in the host does not prevent normal operation.
+         */
+        warn_report_err(err);
+    }
+
     return;
 
 error:
@@ -187,6 +215,7 @@ static void vfio_ap_unrealize(DeviceState *dev)
     VFIOAPDevice *vapdev = VFIO_AP_DEVICE(dev);
 
     vfio_ap_unregister_irq_notifier(vapdev, VFIO_AP_REQ_IRQ_INDEX);
+    vfio_ap_unregister_irq_notifier(vapdev, VFIO_AP_CFG_CHG_IRQ_INDEX);
     vfio_detach_device(&vapdev->vdev);
     g_free(vapdev->vdev.name);
 }
-- 
2.39.5 (Apple Git-154)

Re: [RFC PATCH v2 2/5] hw/vfio/ap: notification handler for AP config changed event

[Anthony Krowiak]

On 2/4/25 12:07 PM, Rorie Reyes wrote:
> Register an event notifier handler to process AP configuration
> change events by queuing the event and generating a CRW to let
> the guest know its AP configuration has changed
>
> Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
> ---
>   hw/vfio/ap.c | 29 +++++++++++++++++++++++++++++
>   1 file changed, 29 insertions(+)
>
> diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
> index 30b08ad375..a2b3735349 100644
> --- a/hw/vfio/ap.c
> +++ b/hw/vfio/ap.c
> @@ -18,6 +18,7 @@
>   #include "hw/vfio/vfio-common.h"
>   #include "system/iommufd.h"
>   #include "hw/s390x/ap-device.h"
> +#include "hw/s390x/css.h"
>   #include "qemu/error-report.h"
>   #include "qemu/event_notifier.h"
>   #include "qemu/main-loop.h"
> @@ -37,6 +38,7 @@ struct VFIOAPDevice {
>       APDevice apdev;
>       VFIODevice vdev;
>       EventNotifier req_notifier;
> +    EventNotifier cfg_notifier;
>   };
>   
>   OBJECT_DECLARE_SIMPLE_TYPE(VFIOAPDevice, VFIO_AP_DEVICE)
> @@ -70,6 +72,16 @@ static void vfio_ap_req_notifier_handler(void *opaque)
>       }
>   }
>   
> +static void vfio_ap_cfg_chg_notifier_handler(void *opaque)
> +{
> +    VFIOAPDevice *vapdev = opaque;
> +
> +    if (!event_notifier_test_and_clear(&vapdev->cfg_notifier)) {
> +        css_generate_css_crws(0);

In patch 3/5, you move the css_generate_css_crws() function outside
of this if block and replace it with a return here. That is the right thing
to do, but you should do it here in this patch.

> +    }
> +
> +}
> +
>   static bool vfio_ap_register_irq_notifier(VFIOAPDevice *vapdev,
>                                             unsigned int irq, Error **errp)
>   {
> @@ -85,6 +97,10 @@ static bool vfio_ap_register_irq_notifier(VFIOAPDevice *vapdev,
>           notifier = &vapdev->req_notifier;
>           fd_read = vfio_ap_req_notifier_handler;
>           break;
> +    case VFIO_AP_CFG_CHG_IRQ_INDEX:
> +        notifier = &vapdev->cfg_notifier;
> +        fd_read = vfio_ap_cfg_chg_notifier_handler;
> +        break;
>       default:
>           error_setg(errp, "vfio: Unsupported device irq(%d)", irq);
>           return false;
> @@ -136,6 +152,9 @@ static void vfio_ap_unregister_irq_notifier(VFIOAPDevice *vapdev,
>       case VFIO_AP_REQ_IRQ_INDEX:
>           notifier = &vapdev->req_notifier;
>           break;
> +    case VFIO_AP_CFG_CHG_IRQ_INDEX:
> +        notifier = &vapdev->cfg_notifier;
> +        break;
>       default:
>           error_report("vfio: Unsupported device irq(%d)", irq);
>           return;
> @@ -175,6 +194,15 @@ static void vfio_ap_realize(DeviceState *dev, Error **errp)
>           warn_report_err(err);
>       }
>   
> +    if (!vfio_ap_register_irq_notifier(vapdev, VFIO_AP_CFG_CHG_IRQ_INDEX, &err))
> +    {
> +        /*
> +         * Report this error, but do not make it a failing condition.
> +         * Lack of this IRQ in the host does not prevent normal operation.
> +         */
> +        warn_report_err(err);
> +    }
> +
>       return;
>   
>   error:
> @@ -187,6 +215,7 @@ static void vfio_ap_unrealize(DeviceState *dev)
>       VFIOAPDevice *vapdev = VFIO_AP_DEVICE(dev);
>   
>       vfio_ap_unregister_irq_notifier(vapdev, VFIO_AP_REQ_IRQ_INDEX);
> +    vfio_ap_unregister_irq_notifier(vapdev, VFIO_AP_CFG_CHG_IRQ_INDEX);
>       vfio_detach_device(&vapdev->vdev);
>       g_free(vapdev->vdev.name);
>   }

[RFC PATCH v2 3/5] hw/vfio/ap: store object indicating AP config changed in a queue

[Rorie Reyes]

Creates an object indicating that an AP configuration change event
has been received and stores it in a queue. These objects will later
be used to store event information for an AP configuration change
when the CHSC instruction is intercepted.

Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
---
 hw/vfio/ap.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
index a2b3735349..396fcf87de 100644
--- a/hw/vfio/ap.c
+++ b/hw/vfio/ap.c
@@ -41,6 +41,13 @@ struct VFIOAPDevice {
     EventNotifier cfg_notifier;
 };
 
+typedef struct APConfigChgEvent {
+    QTAILQ_ENTRY(APConfigChgEvent) next;
+} APConfigChgEvent;
+
+QTAILQ_HEAD(, APConfigChgEvent) cfg_chg_events =
+    QTAILQ_HEAD_INITIALIZER(cfg_chg_events);
+
 OBJECT_DECLARE_SIMPLE_TYPE(VFIOAPDevice, VFIO_AP_DEVICE)
 
 static void vfio_ap_compute_needs_reset(VFIODevice *vdev)
@@ -75,11 +82,16 @@ static void vfio_ap_req_notifier_handler(void *opaque)
 static void vfio_ap_cfg_chg_notifier_handler(void *opaque)
 {
     VFIOAPDevice *vapdev = opaque;
+    APConfigChgEvent *cfg_chg_event = g_new0(APConfigChgEvent, 1);
 
     if (!event_notifier_test_and_clear(&vapdev->cfg_notifier)) {
-        css_generate_css_crws(0);
+        return;
     }
 
+    QTAILQ_INSERT_TAIL(&cfg_chg_events, cfg_chg_event, next);
+
+    css_generate_css_crws(0);
+
 }
 
 static bool vfio_ap_register_irq_notifier(VFIOAPDevice *vapdev,
-- 
2.39.5 (Apple Git-154)

Re: [RFC PATCH v2 3/5] hw/vfio/ap: store object indicating AP config changed in a queue

[Anthony Krowiak]

On 2/4/25 12:07 PM, Rorie Reyes wrote:
> Creates an object indicating that an AP configuration change event
> has been received and stores it in a queue. These objects will later
> be used to store event information for an AP configuration change
> when the CHSC instruction is intercepted.
>
> Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
> ---
>   hw/vfio/ap.c | 14 +++++++++++++-
>   1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
> index a2b3735349..396fcf87de 100644
> --- a/hw/vfio/ap.c
> +++ b/hw/vfio/ap.c
> @@ -41,6 +41,13 @@ struct VFIOAPDevice {
>       EventNotifier cfg_notifier;
>   };
>   
> +typedef struct APConfigChgEvent {
> +    QTAILQ_ENTRY(APConfigChgEvent) next;
> +} APConfigChgEvent;
> +
> +QTAILQ_HEAD(, APConfigChgEvent) cfg_chg_events =
> +    QTAILQ_HEAD_INITIALIZER(cfg_chg_events);
> +
>   OBJECT_DECLARE_SIMPLE_TYPE(VFIOAPDevice, VFIO_AP_DEVICE)
>   
>   static void vfio_ap_compute_needs_reset(VFIODevice *vdev)
> @@ -75,11 +82,16 @@ static void vfio_ap_req_notifier_handler(void *opaque)
>   static void vfio_ap_cfg_chg_notifier_handler(void *opaque)
>   {
>       VFIOAPDevice *vapdev = opaque;
> +    APConfigChgEvent *cfg_chg_event = g_new0(APConfigChgEvent, 1);
>   
>       if (!event_notifier_test_and_clear(&vapdev->cfg_notifier)) {
> -        css_generate_css_crws(0);
> +        return;

As I stated in my review of patch 2/5, the change above should have
been done there.

>       }
>   
> +    QTAILQ_INSERT_TAIL(&cfg_chg_events, cfg_chg_event, next);
> +
> +    css_generate_css_crws(0);

Ditto.

> +
>   }
>   
>   static bool vfio_ap_register_irq_notifier(VFIOAPDevice *vapdev,

[RFC PATCH v2 4/5] hw/vfio/ap: Storing event information for an AP configuration change event

[Rorie Reyes]

These functions can be invoked by the function that handles interception
of the CHSC SEI instruction for requests indicating the accessibility of
one or more adjunct processors has changed.

Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
---
 hw/vfio/ap.c                 | 38 ++++++++++++++++++++++++++++++++++++
 include/hw/s390x/ap-bridge.h | 22 +++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
index 396fcf87de..1ec5d1a64c 100644
--- a/hw/vfio/ap.c
+++ b/hw/vfio/ap.c
@@ -94,6 +94,44 @@ static void vfio_ap_cfg_chg_notifier_handler(void *opaque)
 
 }
 
+int ap_chsc_sei_nt0_get_event(void *res)
+{
+    APConfigChgEvent *cfg_chg_event = QTAILQ_FIRST(&cfg_chg_events);
+    ChscSeiNt0Res *nt0_res  = (ChscSeiNt0Res *)res;
+
+    memset(nt0_res, 0, sizeof(*nt0_res));
+
+    if (!cfg_chg_event) {
+        return 1;
+    }
+
+    QTAILQ_REMOVE(&cfg_chg_events, cfg_chg_event, next);
+    g_free(cfg_chg_event);
+
+    /*
+     * If there are any AP configuration change events in the queue,
+     * indicate to the caller that there is pending event info in
+     * the response block
+     */
+    if (ap_chsc_sei_nt0_have_event()) {
+        nt0_res->flags |= PENDING_EVENT_INFO_BITMASK;
+    }
+
+    nt0_res->length = sizeof(ChscSeiNt0Res);
+    nt0_res->code = NT0_RES_RESPONSE_CODE;
+    nt0_res->nt = NT0_RES_NT_DEFAULT;
+    nt0_res->rs = NT0_RES_RS_AP_CHANGE;
+    nt0_res->cc = NT0_RES_CC_AP_CHANGE;
+
+    return 0;
+
+}
+
+int ap_chsc_sei_nt0_have_event(void)
+{
+    return !QTAILQ_EMPTY(&cfg_chg_events);
+}
+
 static bool vfio_ap_register_irq_notifier(VFIOAPDevice *vapdev,
                                           unsigned int irq, Error **errp)
 {
diff --git a/include/hw/s390x/ap-bridge.h b/include/hw/s390x/ap-bridge.h
index 470e439a98..f4d838bf99 100644
--- a/include/hw/s390x/ap-bridge.h
+++ b/include/hw/s390x/ap-bridge.h
@@ -16,4 +16,26 @@
 
 void s390_init_ap(void);
 
+typedef struct ChscSeiNt0Res {
+    uint16_t length;
+    uint16_t code;
+    uint8_t reserved1;
+    uint16_t reserved2;
+    uint8_t nt;
+#define PENDING_EVENT_INFO_BITMASK 0x80;
+    uint8_t flags;
+    uint8_t reserved3;
+    uint8_t rs;
+    uint8_t cc;
+} QEMU_PACKED ChscSeiNt0Res;
+
+#define NT0_RES_RESPONSE_CODE 1;
+#define NT0_RES_NT_DEFAULT    0;
+#define NT0_RES_RS_AP_CHANGE  5;
+#define NT0_RES_CC_AP_CHANGE  3;
+
+int ap_chsc_sei_nt0_get_event(void *res);
+
+int ap_chsc_sei_nt0_have_event(void);
+
 #endif
-- 
2.39.5 (Apple Git-154)

[RFC PATCH v2 5/5] s390: implementing CHSC SEI for AP config change

[Rorie Reyes]

Handle interception of the CHSC SEI instruction for requests
indicating the guest's AP configuration has changed.

Signed-off-by: Rorie Reyes <rreyes@linux.ibm.com>
Reviewed-by: Anthony Krowiak <akrowiak@linux.ibm.com>
Tested-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 target/s390x/ioinst.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/target/s390x/ioinst.c b/target/s390x/ioinst.c
index a944f16c25..f061c6db14 100644
--- a/target/s390x/ioinst.c
+++ b/target/s390x/ioinst.c
@@ -17,6 +17,7 @@
 #include "trace.h"
 #include "hw/s390x/s390-pci-bus.h"
 #include "target/s390x/kvm/pv.h"
+#include "hw/s390x/ap-bridge.h"
 
 /* All I/O instructions but chsc use the s format */
 static uint64_t get_address_from_regs(CPUS390XState *env, uint32_t ipb,
@@ -573,13 +574,19 @@ out:
 
 static int chsc_sei_nt0_get_event(void *res)
 {
-    /* no events yet */
+    if (s390_has_feat(S390_FEAT_AP)) {
+        return ap_chsc_sei_nt0_get_event(res);
+    }
+
     return 1;
 }
 
 static int chsc_sei_nt0_have_event(void)
 {
-    /* no events yet */
+    if (s390_has_feat(S390_FEAT_AP)) {
+        return ap_chsc_sei_nt0_have_event();
+    }
+
     return 0;
 }
 
-- 
2.39.5 (Apple Git-154)