Re: [Qemu-devel] [PATCH v2 1/2] virtio: Add function to check whether backend supports VIRTIO_1

[Maxime Coquelin]

On 09/09/2016 07:47 PM, Michael S. Tsirkin wrote:
> On Fri, Sep 09, 2016 at 08:00:31PM +0300, Marcel Apfelbaum wrote:
> > On 09/09/2016 04:10 PM, Maxime Coquelin wrote:
> > > This patch adds virtio_test_backend_virtio_1() function to
> > > check whether backend supports VIRTIO_F_VERSION_1 before the
> > > negociation takes place.
> > >
> > > Cc: Cornelia Huck <address@hidden>
> > > Cc: Marcel Apfelbaum <address@hidden>
> > > Cc: Michael S. Tsirkin <address@hidden>
> > > Cc: address@hidden
> > > Signed-off-by: Maxime Coquelin <address@hidden>
> > > ---
> > >  hw/virtio/virtio.c         | 13 +++++++++++++
> > >  include/hw/virtio/virtio.h |  1 +
> > >  2 files changed, 14 insertions(+)
> > >
> > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > > index 74c085c..8b30b69 100644
> > > --- a/hw/virtio/virtio.c
> > > +++ b/hw/virtio/virtio.c
> > > @@ -1481,6 +1481,19 @@ void virtio_vmstate_save(QEMUFile *f, void *opaque, 
> > > size_t size)
> > >      virtio_save(VIRTIO_DEVICE(opaque), f);
> > >  }
> > >
> > > +bool virtio_test_backend_virtio_1(VirtIODevice *vdev, Error **errp)
> > > +{
> > > +    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> > > +    uint64_t feature;
> > > +
> >
> > I would set "feature = 0" even if doesn't really matter.
> > Anyway:
> >
> > Reviewed-by: Marcel Apfelbaum <address@hidden>
> >
> > Thanks,
> > Marcel
>
> why wouldn't it matter? Looks like an uninitialized variable to me.
Oh yes, you are right, it should be initialized.
Just wait confirmation from Michael on the RFC before sending a v3.

Thanks,
Maxime
> > > +    virtio_add_feature(&feature, VIRTIO_F_VERSION_1);
> > > +
> > > +    assert(k->get_features != NULL);
> > > +    feature = k->get_features(vdev, feature, errp);
> > > +
> > > +    return virtio_has_feature(feature, VIRTIO_F_VERSION_1);
> > > +}
> > > +
> > >  static int virtio_set_features_nocheck(VirtIODevice *vdev, uint64_t val)
> > >  {
> > >      VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> > > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > > index d2490c1..3a31754 100644
> > > --- a/include/hw/virtio/virtio.h
> > > +++ b/include/hw/virtio/virtio.h
> > > @@ -235,6 +235,7 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val);
> > >  void virtio_reset(void *opaque);
> > >  void virtio_update_irq(VirtIODevice *vdev);
> > >  int virtio_set_features(VirtIODevice *vdev, uint64_t val);
> > > +bool virtio_test_backend_virtio_1(VirtIODevice *vdev, Error **errp);
> > >
> > >  /* Base devices.  */
> > >  typedef struct VirtIOBlkConf VirtIOBlkConf;