For qemu, the default vhost drive file is “/dev/vhost-net”, when you configured vhost on.

Give the command “modprobe vhost-net” to add host kernel support for vhost.

This is cannot controlled by libvirt I think.

Wangkai

From: libvirt-users-bounces@redhat.com [mailto:libvirt-users-bounces@redhat.com] On Behalf Of Asadullah Hussain
Sent: Thursday, July 24, 2014 12:43 AM
To: libvirt-users@redhat.com
Subject: [libvirt-users] vhost-net requested but could not be initialized

I am using a custom qemu to launch a vhost enabled VM. The qemu doesn't use the default "/dev/vhost-net" directory as character device. Due to this I am getting the error:

qemu-system-x86_64: -netdev type=tap,id=net1,script=no,downscript=no,ifname=port3,vhost=on: vhost-net requested but could not be initialized

Is there a way to tell libvirt to avoid using the default /dev/vhost-net file?

I have tried using the pass-through arguments but libvirt still processes the command and throws the error.

PS: I can successfully create a vhost VM using qemu command-line, so this is a libvirt issue.

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Cheers, 

Asadullah Hussain