Re: [Qemu-devel] [PATCH] balloon: Do not save VM state wrt asynchronous virtio operations

[Anthony Liguori <aliguori@linux.vnet.ibm.com>]

On 03/09/2010 12:54 PM, Adam Litke wrote:
> When working with the VM state (for loadvm/savevm and migration), it is not
> valid to load and store pointers since the validity of those pointers cannot be
> assured in the new qemu address space.  Therefore, virtio_balloon_save() and
> virtio_balloon_load() must not handle the stats-related fields in struct
> VirtIOBalloon.
>
> If a memory stats request is in-flight at the time of a migration or savevm,
> the request will not complete and should be resubmitted once migration or
> loadvm completes.  Note that this extremely small race window can only be
> triggered using QMP so it is not possible to hang the user monitor.
>
> Signed-off-by: Adam Litke<agl@us.ibm.com>
>    
Applied.  Thanks.

Regards,

Anthony Liguori
> diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
> index 086d9d1..6d12024 100644
> --- a/hw/virtio-balloon.c
> +++ b/hw/virtio-balloon.c
> @@ -261,10 +261,6 @@ static void virtio_balloon_save(QEMUFile *f, void *opaque)
>
>       qemu_put_be32(f, s->num_pages);
>       qemu_put_be32(f, s->actual);
> -    qemu_put_buffer(f, (uint8_t *)&s->stats_vq_elem, sizeof(VirtQueueElement));
> -    qemu_put_buffer(f, (uint8_t *)&s->stats_vq_offset, sizeof(size_t));
> -    qemu_put_buffer(f, (uint8_t *)&s->stats_callback, sizeof(MonitorCompletion));
> -    qemu_put_buffer(f, (uint8_t *)&s->stats_opaque_callback_data, sizeof(void));
>   }
>
>   static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id)
> @@ -278,11 +274,6 @@ static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id)
>
>       s->num_pages = qemu_get_be32(f);
>       s->actual = qemu_get_be32(f);
> -    qemu_get_buffer(f, (uint8_t *)&s->stats_vq_elem, sizeof(VirtQueueElement));
> -    qemu_get_buffer(f, (uint8_t *)&s->stats_vq_offset, sizeof(size_t));
> -    qemu_get_buffer(f, (uint8_t *)&s->stats_callback, sizeof(MonitorCompletion));
> -    qemu_get_buffer(f, (uint8_t *)&s->stats_opaque_callback_data, sizeof(void));
> -
>       return 0;
>   }
>
>
>
>