On 4/9/2018 1:07 AM, Jiri Pirko wrote:
Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudr...@intel.com wrote:
On 4/6/2018 5:48 AM, Jiri Pirko wrote:
Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudr...@intel.com wrote:
[...]

+static int virtnet_bypass_join_child(struct net_device *bypass_netdev,
+                                    struct net_device *child_netdev)
+{
+       struct virtnet_bypass_info *vbi;
+       bool backup;
+
+       vbi = netdev_priv(bypass_netdev);
+       backup = (child_netdev->dev.parent == bypass_netdev->dev.parent);
+       if (backup ? rtnl_dereference(vbi->backup_netdev) :
+                       rtnl_dereference(vbi->active_netdev)) {
+               netdev_info(bypass_netdev,
+                           "%s attempting to join bypass dev when %s already 
present\n",
+                           child_netdev->name, backup ? "backup" : "active");
Bypass module should check if there is already some other netdev
enslaved and refuse right there.
This will work for virtio-net with 3 netdev model, but this check has to be 
done by netvsc
as its bypass_netdev is same as the backup_netdev.
Will add a flag while registering with the bypass module to indicate if the 
driver is doing
a 2 netdev or 3 netdev model and based on that flag this check can be done in 
bypass module
for 3 netdev scenario.
Just let me undestand it clearly. What I expect the difference would be
between 2netdev and3 netdev model is this:
2netdev:
   bypass_master
      /
     /
VF_slave

3netdev:
   bypass_master
      /     \
     /       \
VF_slave   backup_slave

Is that correct? If not, how does it look like?


Looks correct.
VF_slave and backup_slave are the original netdevs and are present in both the 
models.
In the 3 netdev model, bypass_master netdev is created and VF_slave and 
backup_slave are
marked as the 2 slaves of this new netdev.

In the 2 netdev model, backup_slave acts as bypass_master and the bypass module 
doesn't
have access to netdev_priv of the backup_slave.

Once i moved all the ndo_ops of the master netdev to bypass module, i realized 
that we can
move the create/destroy of the upper netdev also to bypass.c.
That way the changes to virtio_net become very minimal.

With these updates, bypass module now supports both the models by exporting 2 
sets of
functions.
3 netdev:
   int bypass_master_create(struct net_device *backup_netdev,
                            struct bypass_master **pbypass_master);
   void bypass_master_destroy(struct bypass_master *bypass_master);


2 netdev:
   int bypass_master_register(struct net_device *backup_netdev, struct 
bypass_ops *ops,
                              struct bypass_master **pbypass_master);
   void bypass_master_unregister(struct bypass_master *bypass_master);

Will send the next revision in a day or two.

Thanks
Sridhar


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