Re: [PATCH 2/2] virtio-balloon: Reject qmp_balloon during hot-unplug

[David Hildenbrand <david@redhat.com>]

On 15.01.20 23:40, Julia Suvorova wrote:
> Hot-unplug takes some time due to communication with the guest.
> Do not change the device while freeing up resources.
> 
> Signed-off-by: Julia Suvorova <jusual@redhat.com>
> ---
>  balloon.c                  | 2 +-
>  hw/virtio/virtio-balloon.c | 9 ++++++++-
>  include/sysemu/balloon.h   | 2 +-
>  3 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/balloon.c b/balloon.c
> index f104b42961..998ec53a0f 100644
> --- a/balloon.c
> +++ b/balloon.c
> @@ -119,5 +119,5 @@ void qmp_balloon(int64_t target, Error **errp)
>      }
>  
>      trace_balloon_event(balloon_opaque, target);
> -    balloon_event_fn(balloon_opaque, target);
> +    balloon_event_fn(balloon_opaque, target, errp);
>  }
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index 57f3b9f22d..0fa4e4454b 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -717,12 +717,19 @@ static void virtio_balloon_stat(void *opaque, BalloonInfo *info)
>                                               VIRTIO_BALLOON_PFN_SHIFT);
>  }
>  
> -static void virtio_balloon_to_target(void *opaque, ram_addr_t target)
> +static void virtio_balloon_to_target(void *opaque, ram_addr_t target,
> +                                     Error **errp)
>  {
> +    DeviceState *bus_dev = qdev_get_bus_device(DEVICE(opaque));
>      VirtIOBalloon *dev = VIRTIO_BALLOON(opaque);
>      VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>      ram_addr_t vm_ram_size = get_current_ram_size();
>  
> +    if (bus_dev && bus_dev->pending_deleted_event) {
> +        error_setg(errp, "Hot-unplug of %s is in progress", vdev->name);
> +        return;
> +    }
> +

How exactly does this help? The guest is free to inflate/deflate
whenever it wants.


-- 
Thanks,

David / dhildenb