Guest OS reports incorrect PCIe Link Speed (5.0 GT/s) for NVMe Passthrough

Products

• VMware vSphere ESXi

Issue/Introduction

If PCIe Gen4 NVMe drives are configured for passthrough to a Virtual Machine running on ESX 9.1, the Guest Operating System incorrectly reports the PCIe link speed as Gen2 (5.0 GT/s).

The following behaviors may be observed within the Guest OS:

• Linux (RHEL): Running the lspci command displays the link status as LnkSta: Speed 5GT/s (ok), Width x32 (ok).

• Windows: Device Manager displays the PCIe speed as Gen2.

Environment

• VMware Cloud Foundation (VCF) 9.x
• ESX 9.x 

Cause

ESX virtualizes the PCIe interface for the guest operating system. The system is designed to present a fixed link speed of 5.0 GT/s to the guest OS regardless of the underlying physical hardware capabilities.

Resolution

• There is no impact on system performance; this anomaly does not throttle or reduce the actual bandwidth or speed of the underlying physical device.
  
  
• Broadcom engineering team has acknowledged this issue and will address it in a future release.
  
  
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