Linux Virtualization - Dec 2017 - [RFC PATCH] virtio_net: Extend virtio to use VF datapath when available

On 12/19/2017 10:41 AM, Stephen Hemminger wrote:
> On Tue, 19 Dec 2017 13:21:17 -0500 (EST)
> David Miller <davem at davemloft.net> wrote:
>
>> From: Stephen Hemminger <stephen at networkplumber.org>
>> Date: Tue, 19 Dec 2017 09:55:48 -0800
>>
>>> could be 10ms, just enough to let udev do its renaming
>> Please, move to some kind of notification or event based handling of
>> this problem.
>>
>> No delay is safe, what if userspace gets swapped out or whatever
>> else might make userspace stall unexpectedly?
>>
> The plan is to remove the delay and do the naming in the kernel.
> This was suggested by Lennart since udev is only doing naming policy
> because kernel names were not repeatable.
>
> This makes the VF show up as "ethN_vf" on Hyper-V which is user
friendly.
>
> Patch is pending.
Do we really need to delay the setup until the name is changed?
Can't we call dev_set_mtu() and dev_open() until dev_change_name() is done?

Thanks
Sridhar

On Tue, 19 Dec 2017 11:42:33 -0800
"Samudrala, Sridhar" <sridhar.samudrala at intel.com> wrote:
> On 12/19/2017 10:41 AM, Stephen Hemminger wrote:
> > On Tue, 19 Dec 2017 13:21:17 -0500 (EST)
> > David Miller <davem at davemloft.net> wrote:
> >  
> >> From: Stephen Hemminger <stephen at networkplumber.org>
> >> Date: Tue, 19 Dec 2017 09:55:48 -0800
> >>  
> >>> could be 10ms, just enough to let udev do its renaming  
> >> Please, move to some kind of notification or event based handling
of
> >> this problem.
> >>
> >> No delay is safe, what if userspace gets swapped out or whatever
> >> else might make userspace stall unexpectedly?
> >>  
> > The plan is to remove the delay and do the naming in the kernel.
> > This was suggested by Lennart since udev is only doing naming policy
> > because kernel names were not repeatable.
> >
> > This makes the VF show up as "ethN_vf" on Hyper-V which is
user friendly.
> >
> > Patch is pending.  
> Do we really need to delay the setup until the name is changed?
> Can't we call dev_set_mtu() and dev_open() until dev_change_name() is
done?
> 
> Thanks
> Sridhar
You can call dev_set_mtu, but when dev_open is done the device name
can not be changed by userspace.

On 12/19/2017 11:46 AM, Stephen Hemminger wrote:
> On Tue, 19 Dec 2017 11:42:33 -0800
> "Samudrala, Sridhar" <sridhar.samudrala at intel.com>
wrote:
>
>> On 12/19/2017 10:41 AM, Stephen Hemminger wrote:
>>> On Tue, 19 Dec 2017 13:21:17 -0500 (EST)
>>> David Miller <davem at davemloft.net> wrote:
>>>   
>>>> From: Stephen Hemminger <stephen at networkplumber.org>
>>>> Date: Tue, 19 Dec 2017 09:55:48 -0800
>>>>   
>>>>> could be 10ms, just enough to let udev do its renaming
>>>> Please, move to some kind of notification or event based
handling of
>>>> this problem.
>>>>
>>>> No delay is safe, what if userspace gets swapped out or
whatever
>>>> else might make userspace stall unexpectedly?
>>>>   
>>> The plan is to remove the delay and do the naming in the kernel.
>>> This was suggested by Lennart since udev is only doing naming
policy
>>> because kernel names were not repeatable.
>>>
>>> This makes the VF show up as "ethN_vf" on Hyper-V which
is user friendly.
>>>
>>> Patch is pending.
>> Do we really need to delay the setup until the name is changed?
>> Can't we call dev_set_mtu() and dev_open() until dev_change_name()
is done?
>>
>> Thanks
>> Sridhar
> You can call dev_set_mtu, but when dev_open is done the device name
> can not be changed by userspace.
I did a quick test to remove the delay and also the dev_open() call and 
i don't see
any issues with virtio taking over the VF datapath.
Only the netdev_info() messages may show old device name.

Any specific scenario where we need to explicitly call? VF's dev_open() 
in the VF setup process?
I tried i40evf driver loaded after virtio_net? AND? virtio_net loading 
after i40evf.

Thanks
Sridhar