WSL2 Nested Virtualization

DataTalk Manager on Windows relies on WSL2, which runs a lightweight VM inside Windows. When Windows itself runs as a guest inside a hypervisor, nested virtualization must be enabled — otherwise WSL2 fails with error 0x800705b4 and DataTalk Manager cannot start its runtime.

Platform support

Proxmox / KVM — supported. Enable the +vmx CPU flag and Hyper-V enlightenments on the physical host.

QEMU (standalone) — supported. Use -cpu host or pass the +vmx flag explicitly.

VMware ESXi / vSphere — supported. Enable Expose hardware-assisted virtualization to the guest OS in VM CPU settings.

VMware Workstation / Fusion — supported. Enable Virtualize Intel VT-x/EPT or AMD-V/RVI in processor settings.

Microsoft Hyper-V — supported. Run Set-VMProcessor -ExposeVirtualizationExtensions $true on the host.

Oracle VirtualBox — limited support, potentially unstable with WSL2. Not recommended for production deployments.

AWS EC2 — supported. Use .metal instance type (standard instance types do not support nested virtualization).

Azure — supported. Use Dv3/Ev3 or newer instance family (B-series burstable VMs do not support nested virtualization).

Proxmox / KVM

Step 1 — Enable nested virtualization on the physical host

Intel CPU:

cat /sys/module/kvm_intel/parameters/nested
echo 'options kvm-intel nested=1' >> /etc/modprobe.d/kvm-intel.conf
modprobe -r kvm_intel && modprobe kvm_intel

AMD CPU:

cat /sys/module/kvm_amd/parameters/nested
echo 'options kvm-amd nested=1' >> /etc/modprobe.d/kvm-amd.conf
modprobe -r kvm_amd && modprobe kvm_amd

A physical host reboot may be required if modprobe -r fails because other VMs are running.

Step 2 — Set VM CPU flags

Apply CPU flags including Hyper-V enlightenments — required for WSL2:

qm set <VMID> -args "-cpu host,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time,hv_synic,hv_stimer,hv_stimer_direct,hv_frequencies,hv_reenlightenment,hv_vpindex,+vmx"

Then fully restart the VM (a Windows reboot is not enough — QEMU must restart):

qm stop <VMID>
qm start <VMID>

Step 3 — Verify inside the Windows guest

Open PowerShell and run:

systeminfo | findstr /i "hyper-v"
bcdedit /enum | findstr -i hypervisor

The hypervisorlaunchtype value must be Auto. If it is missing or Off:

bcdedit /set hypervisorlaunchtype auto

Test WSL2:

wsl --install Ubuntu

A message about a detected hypervisor is normal in nested environments.

VMware ESXi / vSphere

vSphere UI: VM Settings → Virtual Hardware → CPU → enable Expose hardware-assisted virtualization to the guest OS.

ESXi CLI:

vim-cmd vmsvc/power.off <vmid>

Edit the .vmx file and add:

vhv.enable = "TRUE"
hypervisor.cpuid.v0 = "FALSE"

VMware Workstation / Fusion

VM Settings → Processors → check Virtualize Intel VT-x/EPT or AMD-V/RVI.

Microsoft Hyper-V

Run on the Hyper-V host (VM must be shut down first):

Set-VMProcessor -VMName "<YourVMName>" -ExposeVirtualizationExtensions $true

Verify inside the guest:

Get-WmiObject Win32_Processor | Select-Object VirtualizationFirmwareEnabled

Should return True.

Oracle VirtualBox

VM Settings → System → Processor → enable Enable Nested VT-x/AMD-V.

Or via CLI:

VBoxManage modifyvm "<VMName>" --nested-hw-virt on

Windows guest configuration checklist

After enabling nested virtualization at the hypervisor level, verify the Windows guest is correctly configured:

Hyper-V launch type — run bcdedit /enum | findstr -i hypervisor and confirm hypervisorlaunchtype Auto.

WSL feature — run dism /online /get-featureinfo /featurename:Microsoft-Windows-Subsystem-Linux and confirm State: Enabled.

VM Platform — run dism /online /get-featureinfo /featurename:VirtualMachinePlatform and confirm State: Enabled.

Hypervisor Platform — run Get-WindowsOptionalFeature -Online -FeatureName HypervisorPlatform and confirm State: Enabled.

WSL version — run wsl --version and confirm WSL version: 2.x.x.

Nested VM test — run wsl --install Ubuntu and confirm it completes without error.

Enable Hypervisor Platform if it is missing:

DISM /Online /Enable-Feature /All /FeatureName:HypervisorPlatform

Downgrade WSL if needed

WSL version 2.7.8 has a confirmed regression. If WSL fails after an automatic update, downgrade to 2.7.3:

Get-AppxPackage -AllUsers | Where-Object { $_.PackageFamilyName.contains("MicrosoftCorporationII.WindowsSubsystemForLinux") } | Remove-AppxPackage -AllUsers

mkdir C:\Temp
curl.exe -L -o C:\Temp\wsl273.msi https://github.com/microsoft/WSL/releases/download/2.7.3/wsl.2.7.3.0.x64.msi

msiexec /i C:\Temp\wsl273.msi /L*VX C:\Temp\wsllog.txt

To prevent automatic WSL updates from overwriting the working version, block updates via Group Policy: HKLM\SOFTWARE\Policies\Microsoft\Windows\WSL.

WSL2 memory limits

WSL2 uses up to 80 % of available RAM by default. On machines with limited memory, set explicit limits.

Create or edit the file at C:\Users\mySCADAsrv\.wslconfig:

[wsl2]
memory=8GB
processors=2
swap=2GB

Apply changes:

wsl --shutdown

Recommended allocation:

8 GB VM RAM — set memory=4GB.

16 GB VM RAM — set memory=8GB.

32 GB VM RAM — set memory=12GB.

Leave at least 4–6 GB free for Windows and the DataTalk Manager application.

Common error codes

0x800705b4 — nested VM creation timed out. Enable nested virtualization at the hypervisor, verify the Windows guest flags, and downgrade WSL to 2.7.3 if needed.

0x8000000d — stuck WSL registration. Run wsl --unregister <distro> and delete the Lxss registry key.

ERROR_FILE_EXISTS — old VHDX file remains at the import path. Delete …\Runtime<distro>\wslDiskStorage and retry.

WSL_E_DISTRO_NOT_FOUND — the distro was registered under a different Windows user. Re-import under the mySCADAsrv service account.

ERROR_FILE_NOT_FOUND — WSL kernel is missing. Reinstall the WSL MSI package.

0x80070005 — permission denied. Ensure the operation runs as the service account that owns the WSL distros.