Description

If K8S + kubevirt is installed on Flatcar 3850.0.0+, the allocatable vhost-net devices are 0.

Impact

This issue impacts creating k8s kubevirt vms (no vms can be created if there are no allocatable vhost-net devices).

Environment and steps to reproduce

My environment was a k8s created on baremetal ARM64 using Flatcar 3850.0.0 stock image and automation from https://github.com/cloudbase/BMK/tree/flatcar_sysext.

Expected behavior

$: kubect get node -A -o yaml | grep -i vhost-net
allocatable: devices.kubevirt.io/vhost-net: 1k

Additional information

If the node is rebooted, the vhost-net allocatable devices are back to the expected size.
Sometimes, the issue cannot be reproduced, which means it is a race condition.
The issue is not present on the current stable or beta releases.

When trying to debug this issue, saw that the kubevirt implementation tries to open the /dev/vhost-net device file in order for the vhost-net kernel module to be autoloaded. I have created a small golang test script and I can confirm that opening the device file does not autoload the kernel module. More debug is needed to see if the 6.6 Linux kernel has module autoload disabled?