On Wed, Mar 26, 2014 at 08:59:04AM +0000, Wangrui (K) wrote:
> Hi,
>
> I use ethernet vif for VM (libvirt 1.1.0 qemu 1.5.1). xml as such
>
> <interface type='ethernet'>
> <script path='' />
> <target dev='tap_mq'/>
> <mac address='52:54:00:19:9e:4e'/>
> <model type='virtio' />
> <driver name='vhost' queues='2'/>
> </interface>
>
> tap_mq is a tap device with multi_queue property which was created on
> host by ip command, such as follows
> #ip tuntap add tap_mq mode tap multi_queue
>
> I want to use multiple queue feature for this vif so I set queues='2' in
> xml.
>
> When start VM , an error occurs
> "error: unsupported configuration: Multiqueue network is not supported
> for: ethernet".
> This error is reported from function qemuBuildInterfaceCommandLine
>
> /* Currently nothing besides TAP devices supports multiqueue. */
> if (net->driver.virtio.queues > 0 &&
> !(actualType == VIR_DOMAIN_NET_TYPE_NETWORK ||
> actualType == VIR_DOMAIN_NET_TYPE_BRIDGE)) {
> virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> _("Multiqueue network is not supported for: %s"),
> virDomainNetTypeToString(actualType));
> return -1;
> }
>
> The comment specifies that only TAP device supports multiqueue. But
> VIR_DOMAIN_NET_TYPE_ETHERNET is also TAP device I think.
No, libvirt can't assume that - it just knows it is something that /looks/
like a tap device but it might not be. This is just an example of one of
the many problems with type=ethernet and why we recommend people never
to use this & why its taints any domain using it.
Regards,
Daniel
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