Open a terminal and type the following: Sudo modprobe -r kvm_amd kvm This will remove the module, and any dependencies it needs.

This error is because you have virtualbox and kvm installed. The kernel modules conflict.

The "simple" solution is to use one or the other, but not both. You can, however, use both as long as you are willing to manually (or script) loading / unloading the kernel modules.

To see your modules

#Virtualbox modules
sudo lsmod | grep vbox

#kvm
sudo lsmod| grep kvm

To remove a module

# remove virtualbox
sudo rmmod vboxdrv
sudo rmmod vboxnetflt

#remove kvm
sudo rmmod kvm
sudo rmmod kvm_amd

use insmod

sudo insmod /full/path/to/your/modules

You can find the module with

locate kvm | grep .ko
locate vbox | grep .ko

Use the modules for your current kernel.

Execute this:

$ VBoxManage modifyvm <VirtualMachineName> --nested-hw-virt on

In version 6.12 of the Linux kernel, kvm module initialisation was changed — it now takes place as soon as the modules are loaded, and not the first time they are used. This prevents VirtualBox from working, as you discovered. This is documented in the VirtualBox 7.1.4 release notes. Since your system was upgraded from 6.11 to 6.14, that explains the sudden appearance of the symptoms.

To return to the previous situation (where KVM modules can be loaded without preventing VirtualBox from working), you can add kvm.enable_virt_at_load=0 to the kernel boot parameters. If you’re using Grub on a Debian derivative, that’s done by adding the parameter to the GRUB_CMDLINE_LINUX_DEFAULT= line in /etc/default/grub, then running sudo update-grub. After a reboot, this will allow VirtualBox to work, without preventing any other KVM-based tool from working either.

The other option is to disable the KVM modules entirely; this is safe, but will prevent any KVM-based tool from working. See cas’ answer for details.

Perhaps you were previously running in 32bit mode? Most motherboards don't enable AMD-Virtualization by default, which limits you to 32bit. As others commented, consider GNOME Boxes or Virt-Manager. VirtualBox is not FLOSS and should be avoided where possible.

I found the answer. I had to run the following to unload the kvm_amd module.

sudo rmmod kvm_amd 2>/dev/null

I have no idea why this is true now, but once I ran that command then I was able to start the VirtualBox VM up with no problems.

QEMU

Well, maybe QEMU images run no matter what, because QEMU will still run even when the VirtualBox VM is running and with the kvm_amd module unloaded.

No idea why this module is running and interfering all of a sudden.

Docker

I could also still start my Docker (running MS SQL) without the kvm_amd module running.

Well, all my virtualization seems to be working now. If you run into this problem just unload your associated module

sudo rmmod kvm_amd 2>/dev/null
sudo rmmod kvm_intel 2>/dev/null
sudo rmmod kvm 2>/dev/null

Android Studio Device Emulator

I discovered, however, that for Android Studio device emulator (which I thought ran under QEMU) you will need the kvm loaded in again. (see error I saw when I tried to start the Android Emulator)

To load your KVM module again, you can just run:

sudo modprobe kvm_amd

When you return to Android Studio & try the emulator, it will now run.

I'll be writing scripts to quickly switch between the two.

I finally found the answer. Even if Hyper-v was disabled in the Windows features, the service named HV Host Service was still running. I disabled all the Hyper-v services and now the option VT-x / AMD-V in the Vbox VM setting isn't grayed out anymore and my VM boots when I enable the option.

On my setup (AMD Ryzen / MSI B450M-A PRO MAX), /proc/cpuinfo listed the svm feature, and lscpu listed AMD-V, even though it was disabled in the BIOS.

The BIOS setting to enable AMD-V was hard to find, as it was located in Overclocking > CPU Features > SVM mode.

Hope this helps people finding this thread.