On Wed, Mar 31, 2021 at 02:11:40PM +0200, Michal Privoznik wrote:
On 3/31/21 1:36 PM, Daniel P. Berrangé wrote:
On Wed, Mar 31, 2021 at 01:09:32PM +0200, Michal Privoznik wrote:
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.
If it is possible to specify a ovs db.socket path in the XML, then why can't this path simply be bind mounted to the right location in the first place.
Because then you'd override the path for system wide OVS. I mean, by default the socket is under /var/run/openvswitch/db.sock and if you have another OVS running inside a container you can expose it under /prefix/var/run/openvswitch/db.sock. ovs-vsctl allows this by --db=$path argument.
Oh, right I was mis-understanding the scenario. I've always thought if we wanted to support use of resources from other namespaces, then that would involve use of a namespace="$PID" attribute to identify the namespace. <source type='unix' namespace="523532" path='/var/lib/vhost_sockets/sock7f9a971a-cf3' mode='server'/> IOW, libvirt could enter the namespace, and then talk to the OVS db.sock at its normal location. It would be bit strange having namespace refer to a different NS for the OVS, but using the path=/var/lib/..... from the current namespace, but as long as we define the semantics clearly its not the end of the world. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|