Re: [Qemu-devel] [PATCH V4 00/22] Multiqueue virtio-net

[Jason Wang <jasowang@redhat.com>]

On 01/31/2013 02:29 AM, Eric Blake wrote:
> On 01/30/2013 04:12 AM, Jason Wang wrote:
>
>> With this changes, user could start a multiqueue virtio-net device through
>>
>> ./qemu -netdev tap,id=hn0,queues=2,vhost=on -device virtio-net-pci,netdev=hn0
>>
>> Management tools such as libvirt can pass multiple pre-created fds/vhostfds through
>>
>> ./qemu -netdev tap,id=hn0,fds=X:Y,vhostfds=M:N -device virtio-net-pci,netdev=hn0
> Do we really need specific fds= parsing, or can we reuse the existing
> -add-fd command line option to our advantage?  I guess what I'm asking
> is how hotplug will work; and if hotplug takes a file name, shouldn't
> the command line also take a name; and if the command line takes a name,
> what's wrong with:
>
> ./qemu -add-fd fdset=1,fd=X -add-fd fdset=2,fd=Y -add-fd fdset=3,fd=M
> -add-fd fdset=4,fd=N -netdev
> tap,id=hn0,fds=/dev/fdset/1:/dev/fdset/2,vhostfds=/dev/fdset/3:/dev/fdset/4
> -device virtio-net-pci,netdev=hn0
>

AFAIK, tap does not support fdset now, so this requirement is beyond the
scope of multiqueue itself. We can do this in the future. Btw does
libvirt support add-fd now?

For hotplug, it just work if you pass multiple file descriptors one by
one through getfd and then use fds=X:Y,vhostfds=M:N.