Re: [Qemu-devel] [PATCH 1/1] virtio-serial-bus: fix guest_connected init before driver init

[Michael S. Tsirkin]

On Tue, Apr 24, 2012 at 03:56:44PM +0530, Amit Shah wrote:
> On (Tue) 24 Apr 2012 [13:17:16], Michael S. Tsirkin wrote:
> > On Tue, Apr 24, 2012 at 02:55:26PM +0530, Amit Shah wrote:
> > > From: Alon Levy <address@hidden>
> > > 
> > > guest_connected should be false before guest driver initialization, and
> > > true after, both for multiport aware and non multiport aware drivers.
> > > 
> > > Don't set it before the guest_features are available; instead use
> > > set_status which is called by io to VIRTIO_PCI_STATUS with
> > > VIRTIO_CONFIG_S_DRIVER_OK by even older non multiport drivers.
> > > 
> > > [Amit: Add comment, tweak summary]
> > 
> > Logic also changed fron Alon's patch. Why?
> 
> Yes, forgot to mention that here.
> 
> > > Signed-off-by: Alon Levy <address@hidden>
> > > Acked-by: Michael S. Tsirkin <address@hidden>
> > > Signed-off-by: Amit Shah <address@hidden>
> > > ---
> > >  hw/virtio-serial-bus.c |   29 +++++++++++++++++++++--------
> > >  1 files changed, 21 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
> > > index e22940e..796224b 100644
> > > --- a/hw/virtio-serial-bus.c
> > > +++ b/hw/virtio-serial-bus.c
> > > @@ -528,6 +528,26 @@ static void set_config(VirtIODevice *vdev, const 
> > > uint8_t *config_data)
> > >      memcpy(&config, config_data, sizeof(config));
> > >  }
> > >  
> > > +static void set_status(VirtIODevice *vdev, uint8_t status)
> > > +{
> > > +    VirtIOSerial *vser;
> > > +    VirtIOSerialPort *port;
> > > +
> > > +    vser = DO_UPCAST(VirtIOSerial, vdev, vdev);
> > > +    port = find_port_by_id(vser, 0);
> > > +
> > > +    if (port && !use_multiport(port->vser)
> > > +        && (status & VIRTIO_CONFIG_S_DRIVER_OK)) {
> > > +        /*
> > > +         * Non-multiport guests won't be able to tell us guest
> > > +         * open/close status.  Such guests can only have a port at id
> > > +         * 0, so set guest_connected for such ports as soon as guest
> > > +         * is up.
> > > +         */
> > > +        port->guest_connected = true;
> > > +    }
> > > +}
> > > +
> > 
> > Weird.  Don't you want to set guest_connected = false when driver
> > is unloaded?
> > This is what Alon's patch did:
> >         port->guest_connected = status & VIRTIO_CONFIG_S_DRIVER_OK;
> 
> Setting guest_connected to false when driver is unloaded is something
> that's not done before this patch (and not noted in the commit log
> too).
> 
> And that case isn't specific to just port 0 (in the !multiport case);
> all ports will have to be updated for such a change.
> 
> Is that something we should do?  It's obviously correct to do that.
> Will it affect anything?  I doubt it.  But needs a separate patch and
> discussion for that change.
> 
>               Amit

Let's not add code to preserve a bug so we can have a discussion.  Let's
have a discussion right here and fix it properly.
BTW guest_connected is not cleared on reset either - a bug too?

-- 
MST