Re: [Qemu-devel] [PATCH] virtio-serial-bus: replay guest_open on migration

[Alon Levy <alevy@redhat.com>]

On Wed, Jul 27, 2011 at 07:45:25AM +0200, Markus Armbruster wrote:
> Alon Levy <alevy@redhat.com> writes:
> 
> > Signed-off-by: Alon Levy <alevy@redhat.com>
> > ---
> >  hw/virtio-serial-bus.c |    8 +++++++-
> >  1 files changed, 7 insertions(+), 1 deletions(-)
> >
> > diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
> > index c5eb931..7a652ff 100644
> > --- a/hw/virtio-serial-bus.c
> > +++ b/hw/virtio-serial-bus.c
> > @@ -618,14 +618,20 @@ static int virtio_serial_load(QEMUFile *f, void *opaque, int version_id)
> >      for (i = 0; i < nr_active_ports; i++) {
> >          uint32_t id;
> >          bool host_connected;
> > +        VirtIOSerialPortInfo *info;
> >  
> >          id = qemu_get_be32(f);
> >          port = find_port_by_id(s, id);
> >          if (!port) {
> >              return -EINVAL;
> >          }
> > -
> >          port->guest_connected = qemu_get_byte(f);
> > +        info = DO_UPCAST(VirtIOSerialPortInfo, qdev, port->dev.info);
> > +        if (port->guest_connected && info->guest_open) {
> > +            /* replay guest open */
> > +            info->guest_open(port);
> > +
> > +        }
> >          host_connected = qemu_get_byte(f);
> >          if (host_connected != port->host_connected) {
> >              /*
> 
> The patch makes enough sense to me, but the commit message is
> insufficient.  Why do you have to replay?  And what's being fixed?

When migrating a host with with a spice agent running the mouse becomes
non operational after the migration. This is rhbz #718463, currently on
spice-server but it seems this is a qemu-kvm issue. The problem is that
after migration spice doesn't know the guest agent is open. Spice is just
a char dev here. And a chardev cannot query it's device, the device has
to let the chardev know when it is open. Right now after migration the
chardev which is recreated is in it's default state, which assumes the
guest is disconnected. Char devices carry no information across migration,
but the virtio-serial does already carry the guest_connected state. This
patch passes that bit to the chardev.