[ovirt-users] feedback and questions about SR-IOV feature

[Michael Burman]

Hello Nathanael

VFs are regular NICs and can be used as regular NICs.
We are allowing to create bond from them and allowing to attach logical
networks to them, because as long as they are not used by any VM, they can
be used just as any other interfaces on the host.

When creating bond from 2 VFs you should see the pencil icon, because you
want to able to edit the bond.
Vf is an interface and you can use it just as you use regular interface on
the host.

* When you create bond from 2 VFs, this VFs are no longer free and you
can't use them to run VM
* The same for attaching a network to VF, this VF is no longer considered
as free VF.

There is no problem about it, this is exactly how it was designed ) , you
have to remember that as long as the VFs are not used by VM, they can be
used as regular NICs and you can do with them everything you want.

http://www.ovirt.org/develop/release-management/features/engine/sr-iov/

Regards,


On Tue, Dec 6, 2016 at 4:23 PM, Nathanaël Blanchet <blanchet at abes.fr> wrote:

>
>
> Le 06/12/2016 à 13:19, Martin Polednik a écrit :
>
>> On 06/12/16 12:14 +0100, Nathanaël Blanchet wrote:
>>
>>> Hello,
>>>
>>> My new 10G NICS support now SR-IOV, and I've played with this new
>>> feature as passthrough device, so as to reduce my host CPU consumption.
>>>
>>> At the origin, I set up a bond on both 10G PF nics.
>>>
>>> After many configurations, the only way I manage to use a VF into a VM,
>>> is to get out of the bond one nic.
>>>
>>> So does it mean that it is impossible to run a VM with VF with PF
>>> attached to a bond?
>>>
>>
>> As far as I know, it's not possible to do that. The reason is that the
>> bond normally creates new (logical) interface, what you are doing is
>> assigning "part" of the bond directly to a VM and the driver within VM
>> isn't aware of the bond.
>>
> This is what I supposed, UI should prevent us to create VFfrom when nic is
> attached to a bond. Pencil icon should'nt appear in this case.
>
>>
>> Moreover, something strange happens : during the boot of the VM, the
>>> passthrough device gets an dhcp IP on the native vlan of the bond, and once
>>> finally up, the real vlan used by this device is on the different
>>> predifined vlan. It implies to me to reconfigure the network to ping
>>> something on the wanted vlan. Really crazy.
>>>
>>
>> This could be explained by previous statement: bonding PFs at
>> hypervisor level and then assigning VFs to a VM can most likely cause
>> undefined behavior.
>>
> The issue is the same when the PF is not attached to a bond, so in an
> expected working situation.
>
>>
>> Other question is : In which case can it be useful to be able to bond 2
>>> VF? UI let us to do so, but it is impossible to add any bridge on that
>>> virtual bond.
>>>
>>
>> At hypervisor level? I believe it doesn't make sense.
>>
> I wonder this because UI allows to do it. The same as above, user
> shouldn't be allowed to bond two VFs, and not allowed to add virtual
> network to a VF
>
>
>> If you require bond between 2 PFs, you can assign 2 VFs each from
>> different PF to a VM and bond them within the guest.
>>
>> Comparing to a large number of restrictions (migration and others), my
>>> opinion is that this feature seems to be very difficult to use in
>>> production...
>>>
>>
>> The use case for SR-IOV is maximum performance at the cost of
>> convenience while still (somewhat) allowing you to scale.
>>
>> --
>>> Nathanaël Blanchet
>>>
>>> Supervision réseau
>>> Pôle Infrastrutures Informatiques
>>> 227 avenue Professeur-Jean-Louis-Viala
>>> 34193 MONTPELLIER CEDEX 5
>>> Tél. 33 (0)4 67 54 84 55
>>> Fax  33 (0)4 67 54 84 14
>>> blanchet at abes.fr
>>>
>>>
>> _______________________________________________
>>> Users mailing list
>>> Users at ovirt.org
>>> http://lists.ovirt.org/mailman/listinfo/users
>>>
>>
>>
> --
> Nathanaël Blanchet
>
> Supervision réseau
> Pôle Infrastrutures Informatiques
> 227 avenue Professeur-Jean-Louis-Viala
> 34193 MONTPELLIER CEDEX 5
> Tél. 33 (0)4 67 54 84 55
> Fax  33 (0)4 67 54 84 14
> blanchet at abes.fr
>
> _______________________________________________
> Users mailing list
> Users at ovirt.org
> http://lists.ovirt.org/mailman/listinfo/users
>



-- 
Michael Burman
RedHat Israel, RHV-M Network QE

Mobile: 054-5355725
IRC: mburman
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