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.
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.
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. 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@abes.fr
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