Windows Virtual Machine fails to boot on Sapphire Rapids CPUs

Environment

• Red Hat Enterprise Linux 9
• Red Hat OpenShift Container Platform 4.x
  • OpenShift Virtualization 4.x
• Intel Sapphire Rapids CPUs
• Microsoft Windows

Issue

• Windows Virtual Machines will not boot after being migrated from VMware
• Windows Virtual Machines will BSOD if set with more than 1 core
• Windows Virtual Machines will BSOD if using Sapphire Rapids, host-model or host-passthrough CPUs.
• Windows Virtual Machines stop booting when enabling WSL/Hyper-V/VBS

Resolution

• Red Hat has found the issue is not present in the latest versions of Windows updates released after January 2025.
  • In Windows 2022, it appears solved by Content from support.microsoft.com is not included.KB5049983.
• As a workaround, set the Virtual Machine with a lower CPU model.

Root Cause

• This is documented in the RHEL 9.6 release notes under Windows VM running on Sapphire Rapids CPU with hypervisor launch type set to auto might fail to boot when restarted, but it not specific to RHEL 9.6.
• Issue is was tracked in This content is not included.RHEL-67699.
• Only Windows Guests using nested virtualization are affected.

Diagnostic Steps

• The Windows Virtual Machine has WSL or VBS enabled.
• The BCD setting hypervisorlaunchtype is set to on or auto.
• The physical node has a Sapphire Rapids CPU
• The VM is using host-model, host-passthrough or named Sappire Rapids CPU model.

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