Multiqueue should be off by default, but its ON. It always matches the number of vCPUs.


This knob does nothing by default

$ oc explain vm.spec.template.spec.domain.devices.blockMultiQueue
GROUP:      kubevirt.io
KIND:       VirtualMachine
VERSION:    v1


FIELD: blockMultiQueue <boolean>

DESCRIPTION:
    Whether or not to enable virtio multi-queue for block devices.
    Defaults to false.    <-----------------

4.20.3

100%

On a VM with >=2 vCPUs (example below has 10 vCPUs):

# oc get vm windows-2022-postgres -o yaml | yq '.spec.template.spec.domain.devices.blockMultiQueue'
false

# oc rsh virt-launcher-windows-2022-postgres-6s257
$ virsh qemu-monitor-command 1 --hmp "info qtree" | grep queues
                num-queues = 10 (0xa).   <--- virtio-blk
                num_queues = 10 (0xa)    <--- virtio-scsi

multiqueue is always enabled, unable to disable it in VM spec.

multiqueue is disabled if blockMultiQueue: false

In the XML add queues='1' on the driver to disable multiqueue, the default on RHEL side is to enable it and match the vCPUs. Doing nothing on the XML doesn't disable it.