VM PCI Slot and Network Interface Changes on upgrade to Virtual Hardware Version 20 or Later
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VM PCI Slot and Network Interface Changes on upgrade to Virtual Hardware Version 20 or Later

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Article ID: 407595

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Updated On:

Products

VMware vSphere ESXi

Issue/Introduction

When a Virtual Machine (VM) is upgraded to Hardware Version 20 or later, the device pci slot number allocation may differ from assignments used in version 20 and earlier.

  • The Guest Operating System (Guest OS) detects "new" hardware, such as network adapters (e.g., ethernet0) or hard drives, on different PCI slots, for example:
    The device “ethernet0” typically assigned at slot ens192(versions 19 and earlier) may change to a different value(eg ens33) as per design.
  • This may impact certain hardcoded configuration via templates regarding virtual devices being assigned to specific PCI slots.

  • The VM may require manual reconfiguration of network settings or disk mount points within the Guest OS.

Environment

VMware vSphere Esxi 8.x
VCF 9.x

Cause

For VMs using EFI firmware with Hardware Version 20 and later, new virtual ACPI motherboard layout is implemented by design when the setting chipset.motherboardLayout='acpi' setting is defined in the VM .vmx file.
This layout supports the vSphere 8.x Virtual NUMA Topology feature but alters the VM’s PCI topology.

Note: Using legacy PCI topology will disable the vNUMA feature and will prevent the physical NUMA topology from being exposed to the guest OS, which might induce performance reductions.


Resolution

The updated ACPI motherboard layout is automatically applied to HWv20 and later EFI VMs without user control. 

Validate the motherboardLayout setting in the VM .vmx file

  • chipset.motherboardLayout='acpi' setting defined in .vmx results in PCI slot changes. 
  • When the setting is not defined in the .vmx file there are no PCI slot changes observed upon upgrade to vHW version 20 or later.

Workaround:

It is recommended to avoid power-on of VM or installing any operating system during the initial VM setup. 

  1. Create a VM with the latest hardware version using BIOS firmware
  2. While the VM is powered off, reconfigure to EFI firmware to retain the legacy PCI topology. (Note that this disables the vNUMA Topology feature)
  3. Removing the chipset.motherboardLayout='acpi' setting from the .vmx file maintains the existing PCI slot configuration, preventing network disconnection on boot.

Note: Hardware versions 20 and earlier is available to support legacy workloads.

Additional Information

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