Windows Server 2025 will not boot in ESXi 8.x Intel Hosts with cluster wide EVC mode enabled.

Products

• VMware vSphere ESXi

Issue/Introduction

• Windows Server 2025 VM powers up on ESXi 8.x host, however it gets stuck in the boot loop.
• This happens in a multi-node cluster with EVC mode enabled. The EVC mode is set to "Intel Merom" specifically.
• The same VM boots normally when migrated to a different cluster without EVC or after disabling EVC in the cluster.
• In the vmware.log of the VM, you see that the guest OS issues a hard reset which is followed by a CPU triple fault "A fault has occurred causing a virtual CPU to enter the shutdown state. If this fault had occurred outside of a virtual machine, it would have caused the virtual machine to restart."

       In(05) vcpu-0 - Tools: Running status rpc handler: 0 => 1.
       In(05) vcpu-0 - Tools: Changing running status: 0 => 1.
       In(05) vcpu-0 - Tools: [RunningStatus] Last heartbeat value 66 (last received 0s ago)
       In(05) vcpu-0 - pvnvram: Failed to retrieve timestamp database data.
       In(05) vcpu-0 - pvnvram: Failed to retrieve timestamp database data.
       In(05) vcpu-0 - SECUREBOOT: Image APPROVED.
       In(05) vcpu-0 - Guest: About to do EFI boot: Windows Boot Manager
       In(05) vcpu-1 - CPU reset: soft (mode Emulation)
       In(05) vcpu-0 - Guest: Firmware has transitioned to runtime.
       In(05)+ vcpu-0 -
       In(05) vcpu-0 - Triple fault.
       In(05) vcpu-0 - MsgHint: msg.monitorEvent.tripleFault
       In(05)+ vcpu-0 - A fault has occurred causing a virtual CPU to enter the shutdown state. If this fault had occurred outside of a virtual machine, it would have caused the physical machine to restart. The shutdown state can be reached by incorrectly configuring the virtual machine, a bug in the guest operating system
         , or a problem in VMware ESX.---------------------------------------
       In(05) vcpu-0 - CPU reset: hard (mode Emulation)
       In(05) vcpu-1 - CPU reset: hard (mode Emulation)
       In(05) vcpu-0 - Chipset: The guest has requested that the virtual machine be hard reset.
       In(05) vcpu-0 - Destroying virtual dev for scsi0:0 vscsi=9225280514171452
       In(05) vcpu-0 - VMMon_VSCSIStopVports: No such target on adapter
       In(05) vcpu-0 - DEVICE: Resetting device 'ALL'.

Environment

VMware vSphere ESXi 8.x

Cause

When using EVC mode with the old set of CPU features (especially Intel Merom), attempting to boot Windows Server 2025 on a newer CPU masquerading as a Merom resulted in an UNSUPPORTED_PROCESSOR BSOD and subsequent triple fault.  

Resolution

The recommendation is not to power up Window Server 2025 on a CPU that is too old. In case of a EVC cluster, please use the EVC mode which supports the minimum requirements for Windows Server 2025. 

See the following for details on those requirements: https://learn.microsoft.com/en-us/windows-server/get-started/hardware-requirements?tabs=cpu&pivots=windows-server-2025