On Wed, 16 May 2012 11:10:47 +0100
"Daniel P. Berrange"<address@hidden> wrote:
From: "Daniel P. Berrange"<address@hidden>
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_change()' 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}}
It's missing an entry in QMP/qmp-events.txt and I have a comment below,
but in general looks good.
Amit, would be good to get your ack.
* balloon.c, balloon.h: Introduce qemu_balloon_change() for
emitting balloon change events on the monitor
* hw/virtio-balloon.c: Invoke qemu_balloon_change() whenever
the guest changes the balloon actual value
* monitor.c, monitor.h: Define QEVENT_BALLOON_CHANGE
Signed-off-by: Daniel P. Berrange<address@hidden>
---
balloon.c | 14 ++++++++++++++
balloon.h | 2 ++
hw/virtio-balloon.c | 5 +++++
monitor.c | 3 +++
monitor.h | 1 +
5 files changed, 25 insertions(+), 0 deletions(-)
diff --git a/balloon.c b/balloon.c
index aa354f7..913862b 100644
--- a/balloon.c
+++ b/balloon.c
@@ -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_change(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;
diff --git a/balloon.h b/balloon.h
index b60fd5d..2ebac0d 100644
--- a/balloon.h
+++ b/balloon.h
@@ -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_change(int64_t actual);
+
#endif
diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
index ce9d2c9..9137573 100644
--- a/hw/virtio-balloon.c
+++ b/hw/virtio-balloon.c
@@ -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_change(ram_size -
+ (dev->actual<< VIRTIO_BALLOON_PFN_SHIFT));
+ }
This can cause several events to be emitted until the memory is adjusted
to the value asked by the user. I'm undecided if this is a feature, but
if I were a client issuing the balloon command I'd expect to get the event
only when the memory is fully adjusted to the value I asked.
Not sure if this possible to implement though, or if we really want it.
}
static uint32_t virtio_balloon_get_features(VirtIODevice *vdev, uint32_t f)
diff --git a/monitor.c b/monitor.c
index 12a6fe2..ef59cd9 100644
--- a/monitor.c
+++ b/monitor.c
@@ -493,6 +493,9 @@ void monitor_protocol_event(MonitorEvent event, QObject
*data)
case QEVENT_WAKEUP:
event_name = "WAKEUP";
break;
+ case QEVENT_BALLOON_CHANGE:
+ event_name = "BALLOON_CHANGE";
+ break;
default:
abort();
break;
diff --git a/monitor.h b/monitor.h
index 0d49800..8de0160 100644
--- a/monitor.h
+++ b/monitor.h
@@ -41,6 +41,7 @@ typedef enum MonitorEvent {
QEVENT_DEVICE_TRAY_MOVED,
QEVENT_SUSPEND,
QEVENT_WAKEUP,
+ QEVENT_BALLOON_CHANGE,
QEVENT_MAX,
} MonitorEvent;