From e855a53f491f73e05e2b6542fb556ad80d45f89e Mon Sep 17 00:00:00 2001

From: Thomas Huth <thuth@redhat.com>

Date: Thu, 17 Oct 2019 08:43:01 +0100

Subject: [PATCH 21/21] s390x/vfio-ap: Implement hot plug/unplug of vfio-ap

 device

RH-Author: Thomas Huth <thuth@redhat.com>

Message-id: <20191017084301.8658-2-thuth@redhat.com>

Patchwork-id: 91819

O-Subject: [RHEL-8.2.0 qemu-kvm PATCH 1/1] s390x/vfio-ap: Implement hot plug/unplug of vfio-ap device

Bugzilla: 1660906

RH-Acked-by: David Hildenbrand <david@redhat.com>

RH-Acked-by: Cornelia Huck <cohuck@redhat.com>

RH-Acked-by: John Snow <jsnow@redhat.com>

From: Tony Krowiak <akrowiak@linux.ibm.com>

Introduces hot plug/unplug support for the vfio-ap device.

To hot plug a vfio-ap device using the QEMU device_add command:

	(qemu) device_add vfio-ap,sysfsdev=$path-to-mdev

	Where $path-to-mdev is the absolute path to the mediated matrix device

	to which AP resources to be used by the guest have been assigned.

A vfio-ap device can be hot plugged only if:

1. A vfio-ap device has not been attached to the virtual machine's ap-bus

   via the QEMU command line or a prior hot plug action.

2. The guest was started with the CPU model feature for AP enabled

   (e.g., -cpu host,ap=on)

To hot unplug a vfio-ap device using the QEMU device_del command:

	(qemu) device_del vfio-ap,sysfsdev=$path-to-mdev

	Where $path-to-mdev is the absolute path to the mediated matrix device

	specified when the vfio-ap device was attached to the virtual machine's

	ap-bus.

A vfio-ap device can be hot unplugged only if:

1. A vfio-ap device has been attached to the virtual machine's ap-bus

   via the QEMU command line or a prior hot plug action.

2. The guest was started with the CPU model feature for AP enabled

   (e.g., -cpu host,ap=on)

Please note that a hot plug handler is not necessary for the vfio-ap device

because the AP matrix configuration for the guest is performed by the

kernel device driver when the vfio-ap device is realized. The vfio-ap device

represents a VFIO mediated device created in the host sysfs for use by a guest.

The mdev device is configured with an AP matrix (i.e., adapters and domains) via

its sysfs attribute interfaces prior to starting the guest or plugging a vfio-ap

device in. When the device is realized, a file descriptor is opened on the mdev

device which results in a callback to the vfio_ap kernel device driver. The

device driver then configures the AP matrix in the guest's SIE state description

from the AP matrix assigned via the mdev device's sysfs interfaces. The AP

devices will be created for the guest when the AP bus running on the guest

subsequently performs its periodic scan for AP devices.

The qdev_simple_device_unplug_cb() callback function is used for the same

reaons; namely, the vfio_ap kernel device driver will perform the AP resource

de-configuration for the guest when the vfio-ap device is unplugged. When the

vfio-ap device is unrealized, the mdev device file descriptor is closed which

results in a callback to the vfio_ap kernel device driver. The device driver

then clears the AP matrix configuration in the guest's SIE state description

and resets all of the affected queues. The AP devices created for the guest

will be removed when the AP bus running on the guest subsequently performs

its periodic scan and finds there are no longer any AP resources assigned to the

guest.

Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>

Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>

Reviewed-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Halil Pasic <pasic@linux.ibm.com>

Tested-by: Pierre Morel <pmorel@linux.ibm.com>

Message-Id: <1550519397-25359-2-git-send-email-akrowiak@linux.ibm.com>

[CH: adapt to changed qbus_set_hotplug_handler() signature]

Signed-off-by: Cornelia Huck <cohuck@redhat.com>

(cherry picked from commit 374b78e37029b05f7ee2f40d0d0aabf5b5b03ce0)

Changed the qbus_set_hotplug_handler() line for RHEL: We do no have

commit 94d1cc5f03a in downstream, so no need for the OBJECT() cast here.

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

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 hw/s390x/ap-bridge.c | 12 +++++++++++-

 hw/vfio/ap.c         |  2 +-

 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/hw/s390x/ap-bridge.c b/hw/s390x/ap-bridge.c

index 3795d30..25a0341 100644

--- a/hw/s390x/ap-bridge.c

+++ b/hw/s390x/ap-bridge.c

@@ -39,6 +39,7 @@ static const TypeInfo ap_bus_info = {

 void s390_init_ap(void)

 {

     DeviceState *dev;

+    BusState *bus;

     /* If no AP instructions then no need for AP bridge */

     if (!s390_has_feat(S390_FEAT_AP)) {

@@ -52,13 +53,18 @@ void s390_init_ap(void)

     qdev_init_nofail(dev);

     /* Create bus on bridge device */

-    qbus_create(TYPE_AP_BUS, dev, TYPE_AP_BUS);

+    bus = qbus_create(TYPE_AP_BUS, dev, TYPE_AP_BUS);

+

+    /* Enable hotplugging */

+    qbus_set_hotplug_handler(bus, dev, &error_abort);

  }

 static void ap_bridge_class_init(ObjectClass *oc, void *data)

 {

     DeviceClass *dc = DEVICE_CLASS(oc);

+    HotplugHandlerClass *hc = HOTPLUG_HANDLER_CLASS(oc);

+    hc->unplug = qdev_simple_device_unplug_cb;

     set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);

 }

@@ -67,6 +73,10 @@ static const TypeInfo ap_bridge_info = {

     .parent        = TYPE_SYS_BUS_DEVICE,

     .instance_size = 0,

     .class_init    = ap_bridge_class_init,

+    .interfaces = (InterfaceInfo[]) {

+        { TYPE_HOTPLUG_HANDLER },

+        { }

+    }

 };

 static void ap_register(void)

diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c

index 3962bb7..a899f8e 100644

--- a/hw/vfio/ap.c

+++ b/hw/vfio/ap.c

@@ -161,7 +161,7 @@ static void vfio_ap_class_init(ObjectClass *klass, void *data)

     set_bit(DEVICE_CATEGORY_MISC, dc->categories);

     dc->realize = vfio_ap_realize;

     dc->unrealize = vfio_ap_unrealize;

-    dc->hotpluggable = false;

+    dc->hotpluggable = true;

     dc->reset = vfio_ap_reset;

     dc->bus_type = TYPE_AP_BUS;

 }

-- 

1.8.3.1