Reboot of a Virtual Machine that using PCI passthrough in a PMem configuration takes long time

Products

• VMware vSphere ESXi

Issue/Introduction

If a virtual machine is using PCI pass-through in a PMem (Persistent Memory) configuration, it will take longer than usual to boot.

This issue occurs during boot-up, regardless of whether a virtual machine is powered off/powered on or restarted.

Environment

VMware ESXi 8.0.x

Cause

In a PMem configuration, multiple WBINVD (Write Back and Invalidate Cache) instructions are executed when OS restarts, which causes the boot process to take longer. Normally, this can be avoided by powering a virtual machine off and on again.

However, when using PCI pass-through, resources are pinned, so this cannot be resolved by powering the virtual machine off and on.

Therefore, when using PCI pass-through in a PMem configuration, the virtual machine will take long time to boot.

Resolution

When using PCI pass-through in a PMEM configuration, it is expected behavior that the virtual machine will take some time to boot.

To reduce the boot time, consider one of the following workarounds:

• Change the PMEM configuration.
• Instead of using PCI passthrough, power the virtual machine off and on again when restarting it.

Additional Information

Japanese Version:
PMem 構成で PCI パススルーを使用する仮想マシンの起動に時間を要する