Re: [Qemu-devel] [PATCH v2 1/2] hw/net/virtio-net: Move DEFINE_VIRTIO_NET_FEATURES to virtio-net

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Mon, 20 Apr 2015 16:20:00 +0800
shannon.zhao@linaro.org wrote:

> From: Shannon Zhao <shannon.zhao@linaro.org>
> 
> Move DEFINE_VIRTIO_NET_FEATURES to the backend virtio-net.
> The transports just sync the host features from backend.
> 
> Signed-off-by: Shannon Zhao <zhaoshenglong@huawei.com>
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> ---
>  hw/net/virtio-net.c            | 4 ++++
>  hw/s390x/s390-virtio-bus.c     | 1 -
>  hw/s390x/virtio-ccw.c          | 1 -
>  hw/virtio/virtio-pci.c         | 1 -
>  include/hw/virtio/virtio-net.h | 1 +
>  5 files changed, 5 insertions(+), 3 deletions(-)

I need the following change to make this work for virtio-ccw:

diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
index 2252789..7a2bdff 100644
--- a/hw/s390x/virtio-ccw.c
+++ b/hw/s390x/virtio-ccw.c
@@ -779,7 +779,6 @@ static void virtio_ccw_net_realize(VirtioCcwDevice *ccw_dev, Error **errp)
     DeviceState *vdev = DEVICE(&dev->vdev);
     Error *err = NULL;
 
-    virtio_net_set_config_size(&dev->vdev, ccw_dev->host_features[0]);
     virtio_net_set_netclient_name(&dev->vdev, qdev->id,
                                   object_get_typename(OBJECT(qdev)));
     qdev_set_parent_bus(vdev, BUS(&ccw_dev->bus));
@@ -790,6 +789,7 @@ static void virtio_ccw_net_realize(VirtioCcwDevice *ccw_dev, Error **errp)
     }
 
     virtio_ccw_device_realize(ccw_dev, VIRTIO_DEVICE(vdev), errp);
+    virtio_net_set_config_size(&dev->vdev, ccw_dev->host_features[0]);
 }
 
 static void virtio_ccw_net_instance_init(Object *obj)

host_features used to be statically populated, so
virtio_net_set_config_size() was able to use the various feature bits
for its decisions.

It does not seem quite right, however, since the set of feature bits
had not been through virtio-net's ->get_features() routine (or the
feature bit manipulations in virtio-ccw's realize() routine) - it was
just good enough.

Maybe the right place for calling set_config_size() would be in a
virtio-net specific ->plugged() callback?

I'm not sure why virtio-pci works, but they have a different topology
with pci device and virtio-pci device separate, so it might work out
there.