EVC Mode displayed without Per-VM EVC mode or Cluster level EVC mode enabled

Products

• VMware vCenter Server

Issue/Introduction

Symptoms:

• EVC Mode displayed without EVC.
• Per-VM EVC mode is not configured in VM(s).
• Cluster-level EVC mode is not configured.
• Virtual machine reports "EVC Mode" data in vSphere Web Client.

Environment

VMware vCenter Server 8.0.x
VMware vCenter Server 7.0.x
VMware vCenter Server 6.7.x

Cause

If Per-VM EVC mode is not enabled, and the ESXi host is either not part of a cluster, or part of a cluster without EVC Mode enabled, the "EVC Mode" for the virtual machine should match the ESXi host's available CPU Instruction set. This "EVC Mode" information is provided to determine the minimum supported host that the VM can be migrated to using vMotion.

Resolution

This is expected behavior.

This 'EVC Mode' is visible on all powered on VMs from vSphere 6.7, whether or not the VMs are in a cluster with a configured EVC baseline, and whether or not the VMs have per-VM-EVC mode configured. The 'EVC Mode' is reporting what CPU features are exposed to the Guest operating system, and the minimum CPU instruction set needed for vMotion.

Usually the EVC setting shown when a VM is powered on is what EVC mode is the minimum the VM can enter, for example: 

• If the VM is on a Broadwell host and power on, it will display "EVC Broadwell". This VM can't migrate to a host less than Broadwell, nor enter an EVC cluster less than Broadwell.
• If the VM is on a Skylake host and power on, it will display "EVC Skylake". This VM can't migrate to a host less than Skylake, nor enter an EVC cluster less than Skylake.
• If the VM is on an Ice Lake host and power on, it will display "EVC Ice Lake". This VM can't migrate to a host less than Ice Lake, nor enter an EVC cluster less than Ice Lake.

However, given that the auto-assigned per-VM EVC mode is set based on the CPU feature set presented to ESXi rather than the actual generation of the physical CPU, there can be cases when the chosen EVC mode is higher than the CPU generation. You might for example have virtual machines running with an automatically set Skylake EVC mode, while their hypervisor-host is actually using a Broadwell CPU, simply because the CPU features made available by BIOS/Microcode are covering all of the ones included in the Skyline EVC mode.

To prevent this from happening, you should explicitly configure a cluster-wide EVC mode suitable for your CPU generation.