[Qemu-devel] [PATCHv2] qdev: DEVICE_DELETED event

["Michael S. Tsirkin" <mst@redhat.com>]

libvirt has a long-standing bug: when removing the device,
it can request removal but does not know when the
removal completes. Add an event so we can fix this in a robust way.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

Changes from v1:
    - move to device_unparent
    - address comments by Andreas and Eric

Andreas also suggested a more generic object-deleted event,
I'm not sure how useful that is so let's add what we already need, for
devices with an id and wait and see what's necessary for non-device
objects?

 QMP/qmp-events.txt        | 15 +++++++++++++++
 hw/qdev.c                 |  7 +++++++
 include/monitor/monitor.h |  1 +
 monitor.c                 |  1 +
 qapi-schema.json          |  4 +++-
 5 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/QMP/qmp-events.txt b/QMP/qmp-events.txt
index b2698e4..f2f115a 100644
--- a/QMP/qmp-events.txt
+++ b/QMP/qmp-events.txt
@@ -136,6 +136,21 @@ Example:
 Note: The "ready to complete" status is always reset by a BLOCK_JOB_ERROR
 event.
 
+DEVICE_DELETED
+-----------------
+
+Emitted whenever the device removal completion is acknowledged
+by the guest. At this point, it's safe to reuse the specified device ID.
+Device removal can be initiated by the guest or by HMP/QMP commands.
+
+Data:
+
+- "device": device name (json-string)
+
+{ "event": "DEVICE_DELETED",
+  "data": { "device": "virtio-net-pci-0" },
+  "timestamp": { "seconds": 1265044230, "microseconds": 450486 } }
+
 DEVICE_TRAY_MOVED
 -----------------
 
diff --git a/hw/qdev.c b/hw/qdev.c
index 689cd54..d603f4f 100644
--- a/hw/qdev.c
+++ b/hw/qdev.c
@@ -29,6 +29,7 @@
 #include "sysemu/sysemu.h"
 #include "qapi/error.h"
 #include "qapi/visitor.h"
+#include "qapi/qmp/qjson.h"
 
 int qdev_hotplug = 0;
 static bool qdev_hot_added = false;
@@ -761,6 +762,12 @@ static void device_unparent(Object *obj)
     DeviceClass *dc = DEVICE_GET_CLASS(dev);
     BusState *bus;
 
+    if (dev->id) {
+        QObject *data = qobject_from_jsonf("{ 'device': %s }", dev->id);
+        monitor_protocol_event(QEVENT_DEVICE_DELETED, data);
+        qobject_decref(data);
+    }
+
     while (dev->num_child_bus) {
         bus = QLIST_FIRST(&dev->child_bus);
         qbus_free(bus);
diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h
index 87fb49c..b868760 100644
--- a/include/monitor/monitor.h
+++ b/include/monitor/monitor.h
@@ -39,6 +39,7 @@ typedef enum MonitorEvent {
     QEVENT_BLOCK_JOB_CANCELLED,
     QEVENT_BLOCK_JOB_ERROR,
     QEVENT_BLOCK_JOB_READY,
+    QEVENT_DEVICE_DELETED,
     QEVENT_DEVICE_TRAY_MOVED,
     QEVENT_SUSPEND,
     QEVENT_SUSPEND_DISK,
diff --git a/monitor.c b/monitor.c
index 32a6e74..2a5e7b6 100644
--- a/monitor.c
+++ b/monitor.c
@@ -457,6 +457,7 @@ static const char *monitor_event_names[] = {
     [QEVENT_BLOCK_JOB_CANCELLED] = "BLOCK_JOB_CANCELLED",
     [QEVENT_BLOCK_JOB_ERROR] = "BLOCK_JOB_ERROR",
     [QEVENT_BLOCK_JOB_READY] = "BLOCK_JOB_READY",
+    [QEVENT_DEVICE_DELETED] = "DEVICE_DELETED",
     [QEVENT_DEVICE_TRAY_MOVED] = "DEVICE_TRAY_MOVED",
     [QEVENT_SUSPEND] = "SUSPEND",
     [QEVENT_SUSPEND_DISK] = "SUSPEND_DISK",
diff --git a/qapi-schema.json b/qapi-schema.json
index 28b070f..bb361e1 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2354,7 +2354,9 @@
 # Notes: When this command completes, the device may not be removed from the
 #        guest.  Hot removal is an operation that requires guest cooperation.
 #        This command merely requests that the guest begin the hot removal
-#        process.
+#        process.  Completion of the device removal process is signaled with a
+#        DEVICE_DELETED event. Guest reset will automatically complete removal
+#        for all devices.
 #
 # Since: 0.14.0
 ##
-- 
MST