[libvirt-users] failure when trying to add a channel device via virsh attach-device

[Peter Krempa]

On Mon, Sep 21, 2015 at 08:16:17 +0000, Jean-Pierre Ribeauville wrote:
> Hi,
> On a KVM host installed with following packages versions  :
> 
> [root at rhel6-roadster test_channels_OK]# rpm -qa | grep libvirt
> libvirt-devel-0.10.2-29.el6.x86_64
> libvirt-0.10.2-29.el6.x86_64
> libvirt-client-0.10.2-29.el6.x86_64
> libvirt-java-0.4.9-1.el6.noarch
> libvirt-java-devel-0.4.9-1.el6.noarch
> libvirt-python-0.10.2-29.el6.x86_64
> [root at rhel6-roadster test_channels_OK]# rpm -qa | grep qemu
> qemu-kvm-0.12.1.2-2.415.el6.x86_64
> gpxe-roms-qemu-0.9.7-6.10.el6.noarch
> qemu-img-0.12.1.2-2.415.el6.x86_64
> [root at rhel6-roadster test_channels_OK]# virsh --version
> 0.10.2
> [root at rhel6-roadster test_channels_OK]#
> 
> 
> When trying to add a channel device via virsh attach-device , I got following errors :
> 
> <channel type='unix'>
>       <source mode='bind' path='//var/lib/libvirt/qemu/omnivision_123456.agent'/>
>       <target type='virtio' name='omnivision_123456.agent' state='disconnected'/>
>       <alias name='channel_OmniVision'/>
>       <address type='virtio-serial' controller='0' bus='0' port='30'/>
> </channel>
> 
> 
> Guest is off :
> 
> 
> [root at rhel6-roadster test_channels_OK]# virsh attach-device Linux_2  add_channel_device.xml
> error: Failed to attach device from add_channel_device.xml
> error: Requested operation is not valid: cannot do live update a device on inactive domain

This was a bug in older versions. In case when the VM is offline you'll
need to explicitly use the '--config' flag so that only the
configuration is updated.

> [root at rhel6-roadster test_channels_OK]#
> 
> 
> Guest is running :
> 
> [root at rhel6-roadster test_channels_OK]# virsh attach-device Linux_2  add_channel_device.xml
> error: Failed to update device from add_channel_device.xml
> error: XML error: unknown device type

The libvirt version you are using does not support character device
hotplug, so you'll not be able to hotplug a channel at this point.

You'll need to use at least libvirt-1.1.1 or a version that backported
commit:

commit 24b0821926ead364a625210940773d7da43f1577
Author: Michal Privoznik <mprivozn at redhat.com>
Date:   Wed Mar 13 11:08:55 2013 +0100

    qemu: Implement chardev hotplug on live level
        
    Since previous patches has prepared everything for us, we
    may now implement live hotplug of a character device.

and the preliminary fixes.

Peter
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