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

[Greg Kurz]

On Mon, 3 Jun 2019 17:03:06 -0400
"Michael S. Tsirkin" <address@hidden> wrote:

> On Mon, Jun 03, 2019 at 10:16:39PM +0200, Greg Kurz wrote:
> > On Wed, 29 May 2019 15:09:52 +0800
> > address@hidden wrote:
> >   
> > > From: Xie Yongji <address@hidden>
> > > 
> > > 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))  
> 
> Or a legacy device I guess?
> 

Do you mean "start_on_kick" should be set for both legacy
and virtio 1.0 transitional devices ?

> > 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 <address@hidden>
> > > ---
> > >  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
> > >      }
> > >  };