Adding a host with Zen5 processor to a Zen4 EVC cluster fails with "The host's CPU hardware does not support the cluster's current Enhanced vMotion Compatibility mode."

Products

• VMware vCenter Server
• VMware vSphere ESX 8.x

Issue/Introduction

• Adding a host with Zen5 processor to a Zen4 EVC cluster fails.
• EPYC 9555, for example, is a support processor of generation Zen5 and can be a member of a Zen4 EVC cluster as per compatibility documents. 
• Error seen when attempting to add such host to the cluster : 

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. Fast short REP MOV is unsupported. Fast string operations (Enhanced REP MOVSB/STOSB) are unsupported. See KB 1003212 for more information. Host is of type: vendor amd family 0x1a model 0x2

• vpxd.log under /var/log/vpxd in vCenter appliance logs error below : 

Running EVC test on xxxxx.hostname.com with evcMode ClusterName,BaselineName
EVCAdmissionFailed: the CPU family/model doesn't support this mode.

 

Environment

vSphere 8.x

Cause

This occurs if Enhanced REP MOVSB/STOSB and Fast Short REP MOVSB options are disabled in the hardware BIOS. 

Resolution

Enable both Enhanced REP MOVSB/STOSB and Fast Short REP MOVSB options under the hardware BIOS > Processor settings. 
Follow Hardware vendor's instructions to enable these options from BIOS.