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

[Shannon Zhao]

On 2015/4/20 19:32, Cornelia Huck wrote:
On Mon, 20 Apr 2015 16:20:00 +0800
shannon.z...@linaro.org wrote:

From: Shannon Zhao <shannon.z...@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 <zhaoshengl...@huawei.com>
Signed-off-by: Shannon Zhao <shannon.z...@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.


The virtio-pci works because it calls device_plugged hook to get the 
features and this hook is called before realized function. When calling 
virtio_net_set_config_size the features are already synced, so it works.

I think maybe we should call device_plugged hook to get the features in 
virtio-ccw other than get them in realized function. So the virtio-ccw, 
virtio-pci and virtio-mmio use same ways.

Thanks,
Shannon