Re: [Libvirt] Attach qemu commands to an running xml domain

On 3/30/21 11:35 AM, Waleed Musa wrote: > Hi all, > > I see in libvirt you are supporting attach/detach devices to existing > xml domain using *attachDeviceFlags *and *detachDeviceFlags *APIs. > Now we are adding some qemu command to the xml domain related to some > interfaces using alias names before starting the VM, but we will face an > issue with hot plug such devices, so I have two question here: > > 1. Is it applicable to set the alias names for interfaces because I saw > it's ignored when I add it to xml domain before starting the VM? > 2. Is there a way or API to attach qemu commands to running domain as > you are doing in attaching the device using *attachDeviceFlags?* > > *Example of my xml* > *<domain type='kvm' id='5' > xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'> > * > *  <devices> > * >     <interface type='vhostuser'> >       <mac address='fa:16:3e:ac:12:4c'/> >       <source type='unix' > path='/var/lib/vhost_sockets/sockbbb6bbe9-eb5' mode='server'/> >       <target dev='tapbbb6bbe9-eb'/> >       <model type='virtio'/> >       <driver queues='4' rx_queue_size='512' tx_queue_size='512'/> >       <alias name='net0'/> >       <address type='pci' domain='0x0000' bus='0x00' slot='0x03' > function='0x0'/> >     </interface> > *  </devices> > * > *  <qemu:commandline>* >     <qemu:arg value='-set'/> >     <qemu:arg value='device.net0.page-per-vq=on'/> >     <qemu:arg value='-set'/> >     <qemu:arg value='device.net0.host_mtu=8942'/> > *  </qemu:commandline>* > *</domain>* Is this perhaps related to the following bug? "interface type='vhostuser' libvirtError: Cannot set interface MTU" https://bugzilla.redhat.com/show_bug.cgi?id=1940559 Are you trying to work around it? I am discussing with Moshe how libvirt can help, but honestly, I don't like the solution I proposed. Long story short, the interface is in different container (among with OVS bridge) and thus when we query ovs-vsctl it connects to the system one and doesn't find that interface. What I proposed was to allow specifying path to ovs db.socket but this would need to be done o per domain basis.