libvirt users - Jul 2014 - Re: 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.

-- 
Cheers,

Asadullah Hussain

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.

--
Cheers,

Asadullah Hussain

Thanks Wangkai but libvirt infact pre-configures network tap devices and
pre-opens /dev/vhost-net file and passes these to qemu as open, ready to
use file descriptors.

My issue is that my qemu requires that /dev/vhost-net directory is removed
and it's kernel module be unloaded. Then it creates a vhost -net device
using its own configuration.


On 24 July 2014 07:35, Wangkai (Kevin,C) <wangkai86@huawei.com> wrote:
>  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.
>
>
>
> --
>
> Cheers,
>
>
>
> Asadullah Hussain
>


-- 
Cheers,

Asadullah Hussain