vhost-user: Fix the virtio features negotiation flaw

This patch aims to fix unexpected negotiation features for
vhost-user netdev interface.

When openvswitch reconnect Qemu after an unexpected disconnection
and Qemu therefore start the vhost_dev, acked_features field in
vhost_dev is initialized with value fetched from acked_features
field in NetVhostUserState, which should be up-to-date at that
moment but Qemu could not make it actually during the time window
of virtio features negotiation.

So we save the acked_features right after being configured by
guest virtio driver so it can be used to restore acked_features
field in vhost_dev correctly.

Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
Signed-off-by: Guoyi Tu <tugy@chinatelecom.cn>
Signed-off-by: Liuxiangdong <liuxiangdong5@huawei.com>
Message-Id: <b9f8cf5561a79ea65ea38960e5a5e6d3707eef0a.1671627406.git.huangy81@chinatelecom.cn>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/net/vhost_net-stub.c

@@ -113,3 +113,8 @@ int vhost_net_virtqueue_restart(VirtIODevice *vdev, NetClientState *nc,
 {
     return 0;
 }
+
+void vhost_net_save_acked_features(NetClientState *nc)
+{
+
+}

hw/net/vhost_net.c

@@ -144,6 +144,15 @@ uint64_t vhost_net_get_acked_features(VHostNetState *net)
     return net->dev.acked_features;
 }
 
+void vhost_net_save_acked_features(NetClientState *nc)
+{
+#ifdef CONFIG_VHOST_NET_USER
+    if (nc->info->type == NET_CLIENT_DRIVER_VHOST_USER) {
+        vhost_user_save_acked_features(nc);
+    }
+#endif
+}
+
 static int vhost_net_get_fd(NetClientState *backend)
 {
     switch (backend->info->type) {

hw/net/virtio-net.c

@@ -984,6 +984,12 @@ static void virtio_net_set_features(VirtIODevice *vdev, uint64_t features)
             continue;
         }
         vhost_net_ack_features(get_vhost_net(nc->peer), features);
+
+        /*
+         * keep acked_features in NetVhostUserState up-to-date so it
+         * can't miss any features configured by guest virtio driver.
+         */
+        vhost_net_save_acked_features(nc->peer);
     }
 
     if (virtio_has_feature(features, VIRTIO_NET_F_CTRL_VLAN)) {

include/net/vhost_net.h

@@ -52,4 +52,6 @@ void vhost_net_virtqueue_reset(VirtIODevice *vdev, NetClientState *nc,
                                int vq_index);
 int vhost_net_virtqueue_restart(VirtIODevice *vdev, NetClientState *nc,
                                 int vq_index);
+
+void vhost_net_save_acked_features(NetClientState *nc);
 #endif