Linux Log: Solving the VERR_VMX_IN_VMX_ROOT_MODE KVM Conflict

The Problem 001

I ran into a blocking error today while setting up a new virtual machine. My goal was to install openSUSE Tumbleweed in VirtualBox on my Linux Mint host system.

As soon as I tried to power on the new Tumbleweed VM, VirtualBox failed and displayed this message:

VirtualBox can't operate in VMX root mode.
Please disable the KVM kernel extension,
recompile your kernel and reboot(VERR_VMX_IN_VMX_ROOT_MODE).
Result Code: NS_ERROR_FAILURE
Component: ConsoleWrap
Interface: IConsole

Root Cause Analysis

After some investigation, the error message itself points directly to the problem. It’s a resource conflict between two hypervisors.

My Linux Mint host system loads the KVM (Kernel-based Virtual Machine) modules at boot by default. Both VirtualBox and KVM require exclusive access to the CPU’s hardware virtualization extensions (Intel VT-x or AMD-V). They cannot operate at the same time.

Since the KVM modules were already loaded and had control of these hardware features, VirtualBox was unable to initialize its virtualization engine.

Solution: Disabling KVM Modules

To get VirtualBox working, I need to prevent the KVM modules from loading. A temporary fix (like sudo rmmod kvm_intel) would be undone on the next reboot, so I'm documenting the permanent solution here for my own reference.

Step 1: Create a modprobe Blacklist File

First, I created a new configuration file in the /etc/modprobe.d/ directory. This tells the system's module loader to ignore specific modules.

sudo nano /etc/modprobe.d/blacklist-kvm.conf

Step 2: Add Modules to the Blacklist

Inside this new file, I added the following two lines. These are the modules that need to be blocked.

blacklist kvm
blacklist kvm_intel

Note: I am on an Intel processor, so I used kvm_intel. If this were an AMD system, the second line would be blacklist kvm_amd.

I saved the file and exited the editor.

Step 3: Update the Initial RAM Filesystem (Initramfs)

This is a critical step. The new blacklist configuration must be baked into the initramfs (the initial boot image) to be effective at the very start of the boot process.

sudo update-initramfs -u

Step 4: Reboot the System

To apply all changes, a full system reboot is necessary.

sudo reboot

Step 5: Verify the Fix

After my Linux Mint host restarted, I opened a terminal to confirm that the KVM modules were no longer loaded.

lsmod | grep kvm

This command returned no output, which confirms that the blacklist is working.

Following this, I launched VirtualBox, and my openSUSE Tumbleweed VM started installation without any errors.