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

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?

[...]

On 4/10/2018 3:55 AM, Jiri Pirko wrote:
> 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?
>
To be exact, 2 netdev model with netvsc looks like this.

     netvsc_netdev
       /
      /
  VF_slave

With virtio_net, 3 netdev model

   bypass_netdev
       /     \
      /       \
VF_slave   virtio_net netdev

Tue, Apr 10, 2018 at 05:13:40PM CEST, sridhar.samudrala at intel.com
wrote:
>On 4/10/2018 3:55 AM, Jiri Pirko wrote:
>> 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?
>> 
>To be exact, 2 netdev model with netvsc looks like this.
>
>    netvsc_netdev
>      /
>     /
> VF_slave
>
>With virtio_net, 3 netdev model
>
>  bypass_netdev
>      /     \
>     /       \
>VF_slave   virtio_net netdev
Could you also mark the original netdev which is there now? is it
bypass_netdev or virtio_net_netdev ?