Patchwork [PATCHv2] qdev: DEVICE_DELETED event

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Submitter Michael S. Tsirkin
Date March 6, 2013, 4:49 p.m.
Message ID <20130306164954.GA331@redhat.com>
Download mbox | patch
Permalink /patch/225550/
State New
Headers show

Comments

Michael S. Tsirkin - March 6, 2013, 4:49 p.m.
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(-)
Andreas Färber - March 6, 2013, 5:03 p.m.
Am 06.03.2013 17:55, schrieb Michael S. Tsirkin:
> On Wed, Mar 06, 2013 at 05:52:05PM +0100, Paolo Bonzini wrote:
>> Il 06/03/2013 17:49, Michael S. Tsirkin ha scritto:
>>> 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?

Fine with me, just wanted to bring that up for consideration since it
impacts not only where we call it but also what data we can provide.

>>> 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);
>>> +    }
>>
>> Do this at the end of device_unparent, so that parents are reported
>> after their children.
>>
>> Paolo
> 
> Hmm yes it seems cleaner, though we'd need to copy the
> id as the device can go away.
> 
> Doing this after
>     while (dev->num_child_bus) {
>         bus = QLIST_FIRST(&dev->child_bus);
>         qbus_free(bus); 
>     }
> would be enough, isn't it?

I had implicitly suggested after dev->realized and before
dev->parent_bus. The reason being that what is inside the if
(dev->realized) {} block actually still needs to be moved into an
unrealize function, and realized = false might still do device-specific
cleanups that could consume time. I'll try to cook something up tonight,
shouldn't collide with your change.

Andreas

Patch

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
 ##