How to enable UEFI firmware storage I/O tracing and logging for VMware virtual machines

Products

• VMware vSphere ESXi

Issue/Introduction

VMware virtual machines utilizing UEFI firmware may encounter boot failures due to I/O path issues. Diagnostic messages such as "No Media Found" or "Operating System Not Found" are frequently observed, but a lack of visibility into the underlying I/O operations makes root cause analysis difficult. Common causes include inaccessible boot media, corrupted partitions, slow I/O response times leading to timeouts, and virtual disk controller failures.

Environment

 

ESXi Version: 9.X

Virtual Hardware Version: 19, 20, or 22

Firmware Type: UEFI

 

Cause

Diagnostic difficulty in boot failure scenarios is caused by a lack of visibility into I/O submissions and completions during the firmware initialization and Boot Device Selection (BDS) phases

Resolution

Enable the I/O tracing mechanism by applying a bitmask to the virtual machine configuration (VMX). This allows the EFI debug logging library to pass storage driver messages into the vmware.log file.

 

1 Power off the virtual machine.

2 Navigate to Edit Settings > VM Options > Advanced > Edit Configuration.

3 Add or modify the following configuration parameter:

         Parameter: efi.fwTrcLogMask

         Value: "0x0017001F"

4 Power on the virtual machine.

5 Review the vmware.log file in the VM directory for entries prefixed with Guest: relating to scsi, nvme, or BDS

6  power off the virtual machine , change the eif.fwTrcLogMask = 0xFFFFFFFF will disable the EFI debug logging trace . 

 

Additional Information

Tracing for Network Boot (PXE) is currently not supported under this mechanism.