virtio: add support for negotiating extended features

The virtio specifications allows for a device features space up
to 128 bits and more. Soon we are going to use some of the 'extended'
bits features for the virtio net driver.

Add support to allow extended features negotiation on a per
devices basis. Devices willing to negotiated extended features
need to implemented a new pair of features getter/setter, the
core will conditionally use them instead of the basic one.

Note that 'bad_features' don't need to be extended, as they are
bound to the 64 bits limit.

Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <9bb29d70adc3f2b8c7756d4e3cd076cffee87826.1758549625.git.pabeni@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
index 11adfbf3ab..cef944e015 100644
--- a/hw/virtio/virtio-bus.c
+++ b/hw/virtio/virtio-bus.c
@@ -62,9 +62,14 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp)
     }
 
     /* Get the features of the plugged device. */
-    assert(vdc->get_features != NULL);
-    vdev->host_features = vdc->get_features(vdev, vdev->host_features,
-                                            &local_err);
+    if (vdc->get_features_ex) {
+        vdc->get_features_ex(vdev, vdev->host_features_ex, &local_err);
+    } else {
+        assert(vdc->get_features != NULL);
+        virtio_features_from_u64(vdev->host_features_ex,
+                                 vdc->get_features(vdev, vdev->host_features,
+                                                   &local_err));
+    }
     if (local_err) {
         error_propagate(errp, local_err);
         return;