Description of problem:

When using SecureBoot tuned reports the following error as debugfs access is restricted:

tuned.utils.commands: Writing to file '/sys/kernel/debug/sched/migration_cost_ns' error: '[Errno 1] Operation not permitted: '/sys/kernel/debug/sched/migration_cost_ns''
tuned.plugins.plugin_scheduler: Error writing value '5000000' to 'migration_cost_ns'

This issue has been reported with the following tickets:

• https://issues.redhat.com/browse/OCPBUGS-19750
• https://issues.redhat.com/browse/OCPBUGS-19768
• https://issues.redhat.com/browse/RHEL-9525

As this is a confirmed limitation of the NTO due to the TuneD component, we should document this as a limitation in the OpenShift Docs:
https://docs.openshift.com/container-platform/4.16/nodes/nodes/nodes-node-tuning-operator.html

Expected Outcome:

• Document that the NTO cannot leverage some of the Tuned features when secureboot is enabled.