[nova] iothread support with Libvirt

Eric K. Miller emiller at genesishosting.com
Thu Jan 6 22:41:37 UTC 2022

> > no there is no way to enable them out of band of nova today.
> > you technially could wrap the qemu binary wiht a script that inject
> parmaters
> > but that obviously would not be supported upstream.
> > but that would be a workaround if you really needed it
> >
> > https://review.opendev.org/c/openstack/devstack/+/817075 is an
> exmaple
> > of such a script

I created a modified version of your script to wrap the qemu-kvm executable, but when OpenStack starts the VM, Nova returns:

2022-01-06 16:15:24.758 6 ERROR nova.compute.manager libvirtError: internal error: Failed to probe QEMU binary with QMP: qemu-kvm.orig: -object iothread,id=iothread0: invalid option

"-object iothread,id=iothread0" is the first argument.

Our Libvirt/QEMU versions are:
Compiled against library: libvirt 4.5.0
Using library: libvirt 4.5.0
Using API: QEMU 4.5.0
Running hypervisor: QEMU 2.12.0

I'm pretty sure these versions includes support for iothreads (for both QEMU as well as Libvirt).

Is Libvirt doing some form of cross-check on the XML parameters with the running QEMU parameters that is incompatible with the wrapper perhaps?


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