[libvirt] Re: Supporting vhost-net and macvtap in libvirt for QEMU

Anthony Liguori aliguori at linux.vnet.ibm.com
Thu Dec 17 19:43:35 UTC 2009

Arnd Bergmann wrote:
> On Thursday 17 December 2009, Daniel P. Berrange wrote:
>> On Wed, Dec 16, 2009 at 07:48:08PM -0600, Anthony Liguori wrote:
>>> The more interesting invocation of vhost-net though is one where the 
>>> vhost-net device backs directly to a physical network card.  In this 
>>> mode, vhost should get considerably better performance than the current 
>>> implementation.  I don't know the syntax yet, but I think it's 
>>> reasonable to assume that it will look something like -net 
>>> tap,dev=eth0.   The effect will be that eth0 is dedicated to the guest.
>> Ok, so in this model you have to create a dedicated ethXX device for
>> every guest, no sharing ?
> I think so, but it could be any of
> * a physical NIC dedicated to the guest, e.g. if you want to run a firewall
>   on that guest and provide connectivity to all other guests to that, or if
>   you have lots of real NICs
> * an IOV adapter with separate physical or virtual functions
> * a VMDq adapter that shows multiple queues on the same PCI function
>   as separate network interfaces
> * a macvlan device in VEPA or bridge mode

I don't think a macvlan device is quite the same thing (mainly because 
there is not finite number of them).  I think <source vepa="on" 
dev="eth0"/> probably would make more sense as a UI.

But then libvirt needs to be able to create/destroy macvlan devices on 


Anthony Liguori

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