Modern CPUs support virtualization (VT-x/AMD-V) and Second Level Address Translation (SLAT/Ept). However, some motherboards have these features . Even if Windows reports that Hyper-V is installed, the hypervisor cannot initialize fully, leading to error 167 on the root partition.
Get-WinEvent -LogName "Microsoft-Windows-Hyper-V-Hypervisor/Admin" | Where-Object $_.Id -eq 167 | Format-List
"The hypervisor did not enable mitigations for side channel vulnerabilities for virtual machines because HyperThreading is enabled." hyper-v-hypervisor 167
: While Event 167 is just a warning, users often find it recorded just before a hard crash or BSOD
An IT admin could not start any VM after a Windows 11 feature update. Event Viewer showed hundreds of event 167 logs. Disabling Core Isolation (Memory Integrity) resolved it instantly. They later re-enabled it but excluded the Hyper-V virtual machine process via Group Policy. They later re-enabled it but excluded the Hyper-V
For VirtualBox:
log generated by the Windows Hyper-V hypervisor. It is typically not a "critical" error on its own, but it frequently appears in System Event Logs alongside other instability issues like system freezes, sound looping, or Kernel-Power 41 crashes Summary of Event ID 167 Microsoft-Windows-Hyper-V-Hypervisor the hypervisor cannot initialize fully
Unlike generic "VM won't start" errors, Event 167 is highly specific to CPU state and security settings. There are four primary triggers:
: This is done in your motherboard's BIOS/UEFI settings. Note that this may slightly reduce multi-threaded performance in exchange for higher security.
: Even if you do not manually run Virtual Machines (VMs), Windows features like Core Isolation (Memory Integrity) Windows Sandbox Windows Subsystem for Linux (WSL)