Linux Virtualization - Apr 2018 - [RFC PATCH net-next v5 3/4] virtio_net: Extend virtio to use VF datapath when available

Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala at intel.com
wrote:
>On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>> Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala at 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?

Thanks!

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

Mon, Apr 09, 2018 at 08:47:06PM CEST, sridhar.samudrala at intel.com
wrote:
>On 4/9/2018 1:07 AM, Jiri Pirko wrote:
>> Sat, Apr 07, 2018 at 12:59:14AM CEST, sridhar.samudrala at intel.com
wrote:
>> > On 4/6/2018 5:48 AM, Jiri Pirko wrote:
>> > > Thu, Apr 05, 2018 at 11:08:22PM CEST, sridhar.samudrala at
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.
You say it looks correct and in another sentence you provide completely
different description. Could you please look again?

[...]