🟡 Medium   ⏱ 5–30 min  Last verified: 20 May 2026
Affected versions: SUSE Linux Enterprise Server 15

📖 ~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

`virsh start` aborts with unsupported CPU model after a hypervisor migration.

Environment & Reproduction

Observed when moving VMs between SLES 15 hypervisors with different CPU generations.

Root Cause Analysis

Guest XML pins a CPU model not present on the destination host.

Quick Triage

Inspect host CPU capabilities with `virsh capabilities` and compare to guest XML.

Step-by-Step Diagnosis

Open the guest definition with `virsh edit` and review “ settings.

Illustrative mockup for sles-15 — kvm_libvirt-cpu-mode_terminal
Terminal diagnostics for KVM guest fails to start with CPU model error — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Switch CPU mode to `host-model` or `host-passthrough` for portability, then start guest.

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Illustrative mockup for sles-15 — kvm_libvirt-cpu-mode_logs
Logs and evidence for KVM guest fails to start with CPU model error — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Pin guests to compatible hypervisors via Salt grain or labels.

Verification & Acceptance Criteria

Guest starts cleanly and `virsh list –all` reports it running.

Rollback Plan

Restore the prior XML if the new mode triggers application-level CPU feature errors.

Prevention & Hardening

Standardise CPU model strategy across the cluster and document migrations.

Pairs with libvirt `qemu unsupported configuration` errors.

Related tutorial: View the step-by-step tutorial for sles-15.

View all sles-15 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

SUSE Virtualization Guide and libvirt CPU model documentation.

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