Ubuntu 22.04 LTS – KVM nested virtualization unavailable on Intel hosts – Fix & Prevention

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Nested guest workloads fail to initialize virtualization features, limiting test and CI capabilities.

Environment & Reproduction

Observed on hosts where nested parameter remains disabled in module defaults.

Root Cause Analysis

kvm_intel loads with nested=0 or BIOS virtualization flags are disabled.

Quick Triage

Verify BIOS VT-x settings and current kernel module parameters.

Step-by-Step Diagnosis

Inspect module options and boot logs for virtualization warnings.

Solution – Primary Fix

Enable nested virtualization in module config and reload KVM modules.

Solution – Alternative Approaches

Use bare-metal CI runners for nested-heavy workloads when host policy disallows nested mode.

Verification & Acceptance Criteria

Nested flag reports Y and nested guest virtualization checks pass.

Rollback Plan

Remove module option file and reload modules to revert nested behavior.

Prevention & Hardening

Bake virtualization parameters into host baseline and validate after kernel updates.

Related Errors & Cross-Refs

Related to libvirt CPU mode incompatibilities and missing hardware virtualization in firmware.

Related tutorial: View the step-by-step tutorial for Ubuntu 22.04 LTS.

View all Ubuntu 22.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

KVM and Ubuntu virtualization documentation for nested scenarios.