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

On 06/12/16 16:58 +0200, Michael Burman wrote: > 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. > That doesn't mean we have the right design: there is no problem in bonding 2 VFs belonging to 2 different PFs; but every sane software warns you if you try to bond 2 VFs from the same PF together (what do you get by such bond?) -- this applies to both host and guest. > http://www.ovirt.org/develop/release-management/features/engine/sr-iov/ > > Regards, > > > On Tue, Dec 6, 2016 at 4:23 PM, Nathanaël Blanchet <blanchet(a)abes.fr&gt; > 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(a)abes.fr >>>> >>>> >>>> _______________________________________________ >>> >>>> Users mailing list >>>> Users(a)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(a)abes.fr >> >> _______________________________________________ >> Users mailing list >> Users(a)ovirt.org >> http://lists.ovirt.org/mailman/listinfo/users >> >> > > > -- > Michael Burman > RedHat Israel, RHV-M Network QE > > Mobile: 054-5355725 > IRC: mburman >