[Qemu-devel] [PATCH v3 3/3] balloon: Don't try fetching info if machine is stopped

[Amit Shah <amit.shah@redhat.com>]

If the machine is stopped and 'info balloon' is invoked, instead of
querying the guest and waiting for a timeout, just display the most
recent stats available in this case and log an error report.

See https://bugzilla.redhat.com/show_bug.cgi?id=623903

Reported-by: <lihuang@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 balloon.c           |   11 +++++++----
 balloon.h           |    6 ++++--
 hw/virtio-balloon.c |    9 +++++++--
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/balloon.c b/balloon.c
index 8e0b7f1..8b05d20 100644
--- a/balloon.c
+++ b/balloon.c
@@ -43,17 +43,20 @@ void qemu_add_balloon_handler(QEMUBalloonEvent *func, void *opaque)
 int qemu_balloon(ram_addr_t target, MonitorCompletion cb, void *opaque)
 {
     if (qemu_balloon_event) {
-        qemu_balloon_event(qemu_balloon_event_opaque, target, cb, opaque);
+        qemu_balloon_event(qemu_balloon_event_opaque, target, cb, opaque,
+                           false);
         return 1;
     } else {
         return 0;
     }
 }
 
-int qemu_balloon_status(MonitorCompletion cb, void *opaque)
+int qemu_balloon_status(MonitorCompletion cb, void *opaque,
+                        bool get_cached_data)
 {
     if (qemu_balloon_event) {
-        qemu_balloon_event(qemu_balloon_event_opaque, 0, cb, opaque);
+        qemu_balloon_event(qemu_balloon_event_opaque, 0, cb, opaque,
+                           get_cached_data);
         return 1;
     } else {
         return 0;
@@ -113,7 +116,7 @@ int do_info_balloon(Monitor *mon, MonitorCompletion cb, void *opaque)
         return -1;
     }
 
-    ret = qemu_balloon_status(cb, opaque);
+    ret = qemu_balloon_status(cb, opaque, !vm_running);
     if (!ret) {
         qerror_report(QERR_DEVICE_NOT_ACTIVE, "balloon");
         return -1;
diff --git a/balloon.h b/balloon.h
index d478e28..729631c 100644
--- a/balloon.h
+++ b/balloon.h
@@ -17,13 +17,15 @@
 #include "monitor.h"
 
 typedef void (QEMUBalloonEvent)(void *opaque, ram_addr_t target,
-                                MonitorCompletion cb, void *cb_data);
+                                MonitorCompletion cb, void *cb_data,
+                                bool get_cached_data);
 
 void qemu_add_balloon_handler(QEMUBalloonEvent *func, void *opaque);
 
 int qemu_balloon(ram_addr_t target, MonitorCompletion cb, void *opaque);
 
-int qemu_balloon_status(MonitorCompletion cb, void *opaque);
+int qemu_balloon_status(MonitorCompletion cb, void *opaque,
+                        bool get_cached_data);
 
 void monitor_print_balloon(Monitor *mon, const QObject *data);
 int do_info_balloon(Monitor *mon, MonitorCompletion cb, void *opaque);
diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
index 309c343..50a1a34 100644
--- a/hw/virtio-balloon.c
+++ b/hw/virtio-balloon.c
@@ -204,7 +204,8 @@ static uint32_t virtio_balloon_get_features(VirtIODevice *vdev, uint32_t f)
 }
 
 static void virtio_balloon_to_target(void *opaque, ram_addr_t target,
-                                     MonitorCompletion cb, void *cb_data)
+                                     MonitorCompletion cb, void *cb_data,
+                                     bool get_cached_data)
 {
     VirtIOBalloon *dev = opaque;
 
@@ -222,8 +223,12 @@ static void virtio_balloon_to_target(void *opaque, ram_addr_t target,
             return;
         }
         dev->stats_callback = cb;
-        dev->stats_opaque_callback_data = cb_data; 
+        dev->stats_opaque_callback_data = cb_data;
         if (dev->vdev.guest_features & (1 << VIRTIO_BALLOON_F_STATS_VQ)) {
+            if (get_cached_data) {
+                show_old_stats(dev);
+                return;
+            }
             qemu_mod_timer(dev->timer, qemu_get_clock(rt_clock) + 5000);
             virtqueue_push(dev->svq, &dev->stats_vq_elem, dev->stats_vq_offset);
             virtio_notify(&dev->vdev, dev->svq);
-- 
1.7.2.2