Virtual machine fails to power on after applying the solution for CVE-2018-3646

Products

• VMware vSphere ESXi 7.0
• VMware vSphere ESXi 8.0

Issue/Introduction

• Enable 'ESXi Side-Channel-Aware Scheduler (SCAv1)' by following the KB  VMware response to ‘L1 Terminal Fault - VMM’ (L1TF - VMM) Speculative-Execution vulnerability in Intel processors for vSphere: CVE-2018-3646,
  
• Then some virtual machines can not power on with below messages:
  
  Operation failed!
Task name Power On virtual machine
Status No host is compatible with the virtual machine.


• Some virtual machines can power on successfully.

Environment

VMware vSphere ESXi 8.0.x
VMware vSphere ESXi 7.0.x

 

Cause

Enabling SCAv1 will result in the vSphere UI reporting only a single logical processor per physical core that halving the number of logical processors if Hyperthreading was previously enabled. In addition Hyperthreading may be reported as 'Disabled' in various configuration tabs. If the virtual machine previously configured vCPU more than physical core, it will not power on due to insufficient logical cores.

Resolution

• The behavior works as designed.
• To workaround the issue, migrate the virtual machine to other ESXi host with sufficient physical CPU core or reduce the vCPU of the virtual machine.