Re: [Qemu-devel] [PATCH 00/16] Add a -netdev option

[Anthony Liguori <anthony@codemonkey.ws>]

Hi Mark,

Mark McLoughlin wrote:
> Hi,
>         Here's a series of patches which gets the ball rolling on adding
> a -netdev option.
>
>         The idea is to de-emphasise the vlan support, and instead make
> a nic directly connected to a host backend the default and recommended
> configuration. We want this because it is only with this configuration
> that we feasibly add optimizations like GSO support or vhost-net.
>   

I think this series is a good first step.  I've looked through the 
patches and they all look pretty good.  I plan on pushing after some 
testing assuming noone objects in the interim.

With respect to moving forward, I wanted to bring up a couple of topics.

To eliminate VLANs, I think the reasonable approach is to implemented an 
emulated hub.  I'd suggest treating the hub like a device.  Instantiate 
it through qdev, support it via -device, etc.  I think it would even be 
reasonable to have it support a fixed number of ports.  I doubt there 
would be any compatibility issues emulating a 32-bit port hub, for instance.

The current syntax would become just a convenient short cut for the 
-netdev syntax along with creating a hub device for each vlan that gets 
instantiated.

I think merging vhost_net support will depend on finishing out the 
netdev work.  Logically, I think vhost_net is a netdev backend and we 
extend the netdev API to support async submission of packets (basically 
mirroring the virtio-net ABI).  In the case of a virtio-net front-end to 
a vhost_net backend, I think we special case that assuming we're running 
kvm.

Regards,

Anthony Liguori