/dev/kvm is missing, even with nestedVirtualization set to true

[andyneff]

Windows Version

Microsoft Windows [Version 10.0.26100.4652]

WSL Version

WSL version: 2.5.9.0

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

Kernel version: 6.6.87.2-1

Distro Version

any

Other Software

No response

Repro Steps

1. Add to /etc/wsl.conf or %UserProfile%\.wslconfig as documented here

[wsl2]
nestedVirtualization=true

2. Restart wsl

Expected Behavior

1. wsl2.nestedVirtualization setting works
2. /dev/kvm exists

Actual Behavior

1. /dev/kvm does not exist
2. When setting in .wslconfig, no errors are printed
   3. When setting in /etc/wsl.conf, upon terminating and restarting the specific wsl distro, you get the following error message:

wsl: Unknown key 'wsl2.nestedVirtualization' in /etc/wsl.conf:7

Diagnostic Logs

No response

[andyneff]

This was last working on June 10, 2025. So not working is a new behavior.

[github-actions]

Logs are required for review from WSL team

If this a feature request, please reply with '/feature'. If this is a question, reply with '/question'.
Otherwise please attach logs by following the instructions below, your issue will not be reviewed unless they are added. These logs will help us understand what is going on in your machine.

How to collect WSL logs

Download and execute collect-wsl-logs.ps1 in an administrative powershell prompt:

Invoke-WebRequest -UseBasicParsing "https://raw.githubusercontent.com/microsoft/WSL/master/diagnostics/collect-wsl-logs.ps1" -OutFile collect-wsl-logs.ps1
Set-ExecutionPolicy Bypass -Scope Process -Force
.\collect-wsl-logs.ps1

The script will output the path of the log file once done.

If this is a networking issue, please use collect-networking-logs.ps1, following the instructions here

Once completed please upload the output files to this Github issue.

Click here for more info on logging
If you choose to email these logs instead of attaching to the bug, please send them to wsl-gh-logs@microsoft.com with the number of the github issue in the subject, and in the message a link to your comment in the github issue and reply with '/emailed-logs'.

[andyneff]

/emailed-logs

[andyneff]

On another computer running WSL version 2.4.13.0, /dev/kvm exists (by default) and is working.

[github-actions]

Diagnostic information

Found '/emailed-logs', adding tag 'emailed-logs'

[benhillis]

@andyneff - you must put this setting into %userprofile%\.wslconfig not /etc/wsl.conf

[andyneff]

@benhillis, ah I see. I'll update the issue description to focus on /dev/kvm missing.

[github-actions]

Logs are required for review from WSL team

If this a feature request, please reply with '/feature'. If this is a question, reply with '/question'.
Otherwise please attach logs by following the instructions below, your issue will not be reviewed unless they are added. These logs will help us understand what is going on in your machine.

How to collect WSL logs

Download and execute collect-wsl-logs.ps1 in an administrative powershell prompt:

Invoke-WebRequest -UseBasicParsing "https://raw.githubusercontent.com/microsoft/WSL/master/diagnostics/collect-wsl-logs.ps1" -OutFile collect-wsl-logs.ps1
Set-ExecutionPolicy Bypass -Scope Process -Force
.\collect-wsl-logs.ps1

The script will output the path of the log file once done.

If this is a networking issue, please use collect-networking-logs.ps1, following the instructions here

Once completed please upload the output files to this Github issue.

Click here for more info on logging
If you choose to email these logs instead of attaching to the bug, please send them to wsl-gh-logs@microsoft.com with the number of the github issue in the subject, and in the message a link to your comment in the github issue and reply with '/emailed-logs'.

[andyneff]

Every up-to-date Windows 11 Machine I've tested with WSL 2.5.9.0, does not have /dev/kvm (which should be on by default anyways).

This is my .wslconfig file

[wsl2]
dnsTunneling=true
nestedVirtualization=true

And I still do not have a /dev/kvm, after running wsl --shutdown to restart WSL.

The only machine I've found to have /dev/kvm was the out of date one running 2.4.13.0. Since I last had this working on my machine on June 10th, and WSL 2.5.9.0 was released on June 9th, it seems possible to me that something might have regressed there or in some other windows update.