Commit 973603a8 authored by Daniel P. Berrangé's avatar Daniel P. Berrangé Committed by Luiz Capitulino
Browse files

Add event notification for guest balloon changes 



After setting a balloon target value, applications have to
continually poll 'query-balloon' to determine whether the
guest has reacted to this request. The virtio-balloon backend
knows exactly when the guest has reacted though, and thus it
is possible to emit a JSON event to tell the mgmt application
whenever the guest balloon changes.

This introduces a new 'qemu_balloon_changed()' API which is
to be called by balloon driver backends, whenever they have
a change in balloon value. This takes the 'actual' balloon
value, as would be found in the BalloonInfo struct.

The qemu_balloon_change API emits a JSON monitor event which
looks like:

  {"timestamp": {"seconds": 1337162462, "microseconds": 814521},
   "event": "BALLOON_CHANGE", "data": {"actual": 944766976}}

* balloon.c, balloon.h: Introduce qemu_balloon_changed() for
  emitting balloon change events on the monitor
* hw/virtio-balloon.c: Invoke qemu_balloon_changed() whenever
  the guest changes the balloon actual value
* monitor.c, monitor.h: Define QEVENT_BALLOON_CHANGE

Signed-off-by: default avatarDaniel P. Berrange <berrange@redhat.com>
Acked-by: default avatarAmit Shah <amit.shah@redhat.com>
Signed-off-by: default avatarLuiz Capitulino <lcapitulino@redhat.com>
parent 395c3b80

QMP/qmp-events.txt

+18 −0
Original line number Diff line number Diff line
@@ -335,3 +335,21 @@ Example: 
               "len": 10737418240, "offset": 134217728,

               "speed": 0 },

     "timestamp": { "seconds": 1267061043, "microseconds": 959568 } }





BALLOON_CHANGE

----------



Emitted when the guest changes the actual BALLOON level. This

value is equivalent to the 'actual' field return by the

'query-balloon' command



Data:



- "actual": actual level of the guest memory balloon in bytes (json-number)



Example:



{ "event": "BALLOON_CHANGE",

    "data": { "actual": 944766976 },

    "timestamp": { "seconds": 1267020223, "microseconds": 435656 } }

balloon.c

+14 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ 
#include "balloon.h"

#include "trace.h"

#include "qmp-commands.h"

#include "qjson.h"



static QEMUBalloonEvent *balloon_event_fn;

static QEMUBalloonStatus *balloon_stat_fn;
@@ -80,6 +81,19 @@ static int qemu_balloon_status(BalloonInfo *info) 
    return 1;

}



void qemu_balloon_changed(int64_t actual)

{

    QObject *data;



    data = qobject_from_jsonf("{ 'actual': %" PRId64 " }",

                              actual);



    monitor_protocol_event(QEVENT_BALLOON_CHANGE, data);



    qobject_decref(data);

}





BalloonInfo *qmp_query_balloon(Error **errp)

{

    BalloonInfo *info;

balloon.h

+2 −0
Original line number Diff line number Diff line
@@ -24,4 +24,6 @@ int qemu_add_balloon_handler(QEMUBalloonEvent *event_func, 
			     QEMUBalloonStatus *stat_func, void *opaque);

void qemu_remove_balloon_handler(void *opaque);



void qemu_balloon_changed(int64_t actual);



#endif

hw/virtio-balloon.c

+5 −0
Original line number Diff line number Diff line
@@ -146,8 +146,13 @@ static void virtio_balloon_set_config(VirtIODevice *vdev, 
{

    VirtIOBalloon *dev = to_virtio_balloon(vdev);

    struct virtio_balloon_config config;

    uint32_t oldactual = dev->actual;

    memcpy(&config, config_data, 8);

    dev->actual = le32_to_cpu(config.actual);

    if (dev->actual != oldactual) {

        qemu_balloon_changed(ram_size -

                             (dev->actual << VIRTIO_BALLOON_PFN_SHIFT));

    }

}



static uint32_t virtio_balloon_get_features(VirtIODevice *vdev, uint32_t f)

monitor.c

+1 −0
Original line number Diff line number Diff line
@@ -443,6 +443,7 @@ static const char *monitor_event_names[] = { 
    [QEVENT_DEVICE_TRAY_MOVED] = "DEVICE_TRAY_MOVED",

    [QEVENT_SUSPEND] = "SUSPEND",

    [QEVENT_WAKEUP] = "WAKEUP",

    [QEVENT_BALLOON_CHANGE] = "BALLOON_CHANGE",

};

QEMU_BUILD_BUG_ON(ARRAY_SIZE(monitor_event_names) != QEVENT_MAX)