ESXi Host Disconnected and EVC Validation Failed After Firmware Update

Products

• VMware vSphere ESXi

Issue/Introduction

After performing a hardware firmware or BIOS update, an ESXi host may exhibit the following behavior:

• The host shows as Disconnected or Not Responding in vCenter Server.
• Attempting to reconnect the host or move it into an EVC-enabled cluster fails.
• The following error is displayed in the vSphere Client:

  The host's CPU hardware does not support the cluster's current Enhanced vMotion Compatibility mode. The host CPU lacks features required by that mode.

• Following errors are observed in /var/log/vmware/vpxd/vpxd.log:

Exception occurred during host sync; EVC validation failed; [vim.HostSystem:host-####, <hostname>], e: N3Vim5Fault33EVCAdmissionFailedCPUModelForMode9Exception

Environment

VMware ESXi 8.0
vCenter Server 8.0

Cause

Firmware updates often reset "System Power Profiles" to factory defaults (e.g., "Max Performance"). On many server platforms, high-performance profiles optimize for low latency by disabling the Monitor/MWAIT CPU instruction.

vCenter EVC modes require the following BIOS features to be explicitly exposed:

1. Monitor/MWAIT (Frequently disabled by "Max Performance" profiles).
2. Intel VT-x or AMD-V (Hardware Virtualization).
3. No-Execute Memory Protection (Intel XD / AMD NX).

Resolution

To restore EVC compatibility:

1. Reboot the host and enter the BIOS/System Setup (typically F9 or F12).
2. Navigate to Power Management or System Profiles.
3. Change the profile from Max Performance to Custom or OS Control.
4. Ensure the following specific settings are Enabled:
   • Monitor/MWAIT
   • Intel Virtualization Technology (VT-x) or AMD-V
   • No-Execute Memory Protection (Intel XD / AMD NX)
5. Save settings and boot ESXi.

6. Verify feature exposure from the ESXi command line: 

   esxcfg-info | grep "HV Support" 

   (A value of 3 confirms all features are enabled).

7. In vCenter, right-click the host and select Connection > Reconnect.

Note: If the issue persists, contact Broadcom Support.

Additional Information

Enabling EVC on a host with an EVC supported processor fails