Re: [Qemu-devel] [PATCH 2/5] virtio: Migrate the "start_on_kick" flag

[Greg Kurz <groug@kaod.org>]

On Wed, 29 May 2019 15:09:52 +0800
elohimes@gmail.com wrote:

> From: Xie Yongji <xieyongji@baidu.com>
> 
> We should migrate the "start_on_kick" flag so that we
> would not miss starting device on kicking at startup
> after migration.
> 

Hmm... IIUC "start_on_kick" means "virtio 1.0 transitional device that has
not been started yet", ie:

!vdev->started &&
(virtio_host_has_feature(vdev, VIRTIO_F_VERSION_1) &&
 !virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1))

If so, not sure why you need this extra field in the first place, but
you probably don't need to migrate it. Just recalculate in a post load
callback.

> Signed-off-by: Xie Yongji <xieyongji@baidu.com>
> ---
>  hw/virtio/virtio.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index fc8fca81ad..4d4ff67791 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -1802,6 +1802,13 @@ static bool virtio_started_needed(void *opaque)
>      return vdev->started;
>  }
>  
> +static bool virtio_start_on_kick_needed(void *opaque)
> +{
> +    VirtIODevice *vdev = opaque;
> +
> +    return vdev->start_on_kick;
> +}
> +
>  static const VMStateDescription vmstate_virtqueue = {
>      .name = "virtqueue_state",
>      .version_id = 1,
> @@ -1941,6 +1948,17 @@ static const VMStateDescription vmstate_virtio_started = {
>      }
>  };
>  
> +static const VMStateDescription vmstate_virtio_start_on_kick = {
> +    .name = "virtio/start_on_kick",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .needed = &virtio_start_on_kick_needed,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_BOOL(start_on_kick, VirtIODevice),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  static const VMStateDescription vmstate_virtio = {
>      .name = "virtio",
>      .version_id = 1,
> @@ -1957,6 +1975,7 @@ static const VMStateDescription vmstate_virtio = {
>          &vmstate_virtio_broken,
>          &vmstate_virtio_extra_state,
>          &vmstate_virtio_started,
> +        &vmstate_virtio_start_on_kick,
>          NULL
>      }
>  };