Nested virtualization bricks Windows guests

[branpurn]

Proxmox 8

Following the wiki documentation here: `https://pve.proxmox.com/wiki/Nested_Virtualization`

This should work, based on the note here: `Note: Microsoft Hyper-V as a nested Hypervisor on AMD CPUs should work with Proxmox VE 7.`

Unfortunately, after installing Windows `Virtual Machine Platform` and other prerequisites for Windows Subsystem for Linux, the system becomes no longer bootable, failing shortly after UEFI hand-off.

Anyone else have similar experience with this?

 

[joshooaj]

Almost a year late but I'm dealing with this right now on a Windows Server 2022 VM running on a Proxmox 8.1.11 host. The host has an Intel CPU and I have nested virtualization enabled. On the same host I'm running linux containers in an Ubuntu 22.04.4 LTS VM.

cat /sys/module/kvm_intel/parameters/nested
Y

The processor type on the ubuntu and windows VMs are both "host", and I've tried with hv-evmcs set to both "default" and "on" with no change.

I have the virtio drivers and QEMU guest agent installed, and have seen the same issue with and without them.

# This doesn't break the Windows boot process
Install-WindowsFeature -Name Microsoft-Windows-Subsystem-Linux

# But this does
Enable-WindowsOptionalFeature -FeatureName VirtualMachinePlatform -Online

# And so does this
Install-WindowsFeature -Name Hyper-V -IncludeAllSubFeature -IncludeManagementTools -Restart

# Some folks have posted that WSL worked after enabling these features and they reference using the dism CLI.
# There shouldn't be a difference enabling the features using PowerShell cmdlets vs dism but just in case there
# is, I tried these too with the same result.
dism.exe /online /enable-feature /featurename:Microsoft-Windows-Subsystem-Linux /all /norestart
dism.exe /online /enable-feature /featurename:VirtualMachinePlatform /all /norestart

# I also came across someone on reddit recommending this but it didn't help either
bcdedit /set hypervisorlaunchtype auto

 

[joshooaj]

I noticed that my Ubuntu VM used SeaBIOS while my Windows VM used OVMF so I spun up a new Windows Server 2022 VM using SeaBIOS and the result is the same. The only difference is when the VM hangs during boot, the splash screen looks like this instead.