LGL-NAX: Rapid Triage for Post-Update GPU Passthrough Failure

Client background

• In 2025Q1, a technology company in Hsinchu Science Park used a PVE setup with NVIDIA consumer GPU passthrough delivered by LGL and operated it internally.
• After update-related failure, LGL engaged WalksCloud for rapid joint triage and evidence-driven diagnosis.

Incident and constraints

• After OS and package updates, passthrough devices could no longer attach and critical VMs failed at boot.
• The site was network-isolated, so no online driver download or package synchronization was possible.
• Timeline pressure required immediate findings for next-step planning.

WalksCloud triage workflow

1. System log analysis

   • Compared pre/post-update dmesg behavior and confirmed GPU enumeration remained visible while passthrough initialization failed.

2. vfio and BIOS verification

   • Revalidated IOMMU grouping, device binding states, and vfio-pci policy application.
   • Cross-checked GPU and PCIe BIOS settings, including secure-boot-related controls, to rule out accidental reset.

3. Rollback-state replay

   • Reapplied known-good configuration and blacklist policies from prior backups.
   • VM boot still failed, confirming issue persistence beyond simple config rollback.

Collaboration model with LGL

• WalksCloud synchronized every triage step in real time with both LGL and the customer.
• Diagnostic evidence (dmesg traces, vfio binding outcomes, and environment constraints) was shared continuously for downstream ownership.
• When further validation became impossible offline, we documented likely driver-version incompatibility and provided a structured continuation path.

Outcome and practical note

• In a fully isolated environment, immediate remediation could not be completed because new driver validation was not available.
• WalksCloud delivered a full triage package and decision-ready hypotheses so LGL could continue with controlled follow-up validation.
• Key lesson: in closed environments, reproducible troubleshooting records are essential to avoid repeated investigative rework.