Red Hat Enterprise Linux 8 VMs revert to Ice Lake EVC mode or show Custom CPU mode on Granite Rapids

Products

• VMware vCenter Server
• VMware Cloud Foundation

Issue/Introduction

• Red Hat Enterprise Linux (RHEL) 8.x virtual machines (VMs) fail to maintain the "Granite Rapids" EVC baseline.
• VMs automatically revert to "Ice Lake" or show a status of "EVC Mode is Custom" with CPU Mode ID Eg:`Custom--cpu-##########`.
• Application instability occurs during vMotion or snapshot operations.
• Windows-based VMs in the same cluster successfully adopt the Granite Rapids baseline.

Environment

• VMware Cloud Foundation 9.x
• vCenter 8.x, 9.x

 

Cause

• According to Red Hat’s official documentation (Red Hat Support for Intel Granite Rapids and Sierra Forest), Intel Granite Rapids processors are only supported on RHEL 9.4 or newer. RHEL 8 and older versions do not, and will not, have the kernel mappings to support Granite Rapids instructions.
• If the cluster EVC baseline or the specific hardware configuration masks these instructions, the guest OS may fail to detect the required features during boot, causing a revert to a lower, stable baseline (Ice Lake) or a custom mode if manual overrides are present.

Resolution

1. Navigate to your Cluster in vCenter and adjust the EVC mode to a supported generation(e.g., "Ice Lake" or "Cascade Lake"). In mixed clusters, set the EVC mode to the highest baseline supported by all hosts.
2. After applying the new EVC baseline, power off and then power on the affected virtual machines.
3. Upgrade the VM hardware version to the latest supported version to ensure compatibility with virtual hardware features.

Note: Contact Redhat Support for more details.

Additional Information

For more details on EVC baselines, see VMware EVC and CPU Compatibility FAQ (313545).