Re: [Qemu-devel] [PATCH V2] balloon: Don't try fetching info if machine is stopped

[Anthony Liguori]

On 08/19/2010 07:48 PM, Amit Shah wrote:
> If the machine is stopped and 'info balloon' is invoked, the monitor
> process just hangs waiting for info from the guest. Return the most
> recent balloon data in that case.
>
> See https://bugzilla.redhat.com/show_bug.cgi?id=623903
>
> Reported-by:<address@hidden>
> Signed-off-by: Amit Shah<address@hidden>
>    

!vm_running is just a special case of an unresponsive guest.  Even if 
the guest was running, if it was oops'd and the administrator didn't 
know, you would have the same issue.

I'd suggest using a timeout based on rt_clock.  If the stats request 
times out, print an appropriate message to the user.

Regards,

Anthony Liguori

> ---
> v2: simplify call to qemu_balloon_status - Paulo
>
>   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 9fe3886..68df891 100644
> --- a/hw/virtio-balloon.c
> +++ b/hw/virtio-balloon.c
> @@ -195,7 +195,8 @@ 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;
>
> @@ -213,8 +214,12 @@ 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) {
> +                complete_stats_request(dev);
> +                return;
> +            }
>               virtqueue_push(dev->svq,&dev->stats_vq_elem, 
> dev->stats_vq_offset);
>               virtio_notify(&dev->vdev, dev->svq);
>           } else {
>