VirtualBox + KVM: Linux Guest Additions: Kernel 6.12 Support – What You Need to Know

KVM's Linux Guest Additions now support kernel 6.12! But there’s a small hiccup. Starting with 6.12, KVM initializes virtualization by default on module load, preventing VirtualBox VMs from starting.

The Issue: KVM vs. VirtualBox

With KVM’s new behavior, VirtualBox will throw the following error:

VirtualBox can't enable the AMD-V extension. Please disable the KVM kernel extension, recompile your kernel and reboot (VERR_SVM_IN_USE).

This happens because KVM hogs the virtualization resources before VirtualBox gets a chance.

The Fix: Two Simple Options

1. Disable KVM’s behavior:

   • Add kvm.enable_virt_at_load=0 to your kernel command line.
   • Edit your bootloader (e.g., GRUB), add the parameter, update, and reboot.

2. Unload KVM modules:

   • Run the following commands before starting your VM:

     sudo modprobe -r kvm_intel  # For Intel CPUs
     sudo modprobe -r kvm_amd   # For AMD CPUs