Why do I have to do `rmmod kvm_intel` in 25.04 to use VirtualBox

Question

I have been using VirtualBox on every regular Ubuntu version from 18.10 to 25.04 as host, i.e. every six months upgrading my Ubuntu host system.

Previously, I never had this problem. But, starting with version 25.04 of Ubuntu, every time I try to start a virtual machine, VirtualBox (ver. 7.0.20_Ubuntu r163906) gives me the error:

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).

This problem can be prevented by doing

# rmmod kvm_intel

before starting VirtualBox.

Why is this so? And what is the recommended action?

The Super User answer VirtualBox can't operate in VMX mode might explain this. It has a suggestion to blacklist kvm_intel to stop it being loaded on boot. This is a comment, and not an answer, as haven't verified it myself. — Chester Gillon, May 18 '25 at 09:58

kyodake · Answer 1 · 2025-07-26T14:16:22.227

12

The Linux kernel, starting with version 6.12, changed the behavior of KVM kernel modules.

They now enable virtualization directly upon module load.

This prevents VirtualBox VMs from starting.

To prevent this, you need to add "kvm.enable_virt_at_load=0" to the kernel command line.

It must be added to /etc/default/grub.

On the line: GRUB_CMDLINE_LINUX_DEFAULT="quiet kvm.enable_virt_at_load=0"

And then run

sudo update-grub
sudo reboot

edited Jul 26 '25 at 14:16

answered May 18 '25 at 13:15

kyodake

18,075

2

Thanks. I will consider this. But, IMHO the default Ubuntu configuration should be such that these tweaks should not be needed. – FedKad May 18 '25 at 13:26
And then reboot the system using "sudo reboot" command. – Omid Estaji Jul 26 '25 at 08:51
@Omid Estaji: Added to the post – kyodake Jul 26 '25 at 14:22
2

More info, see here – mpboden Jul 26 '25 at 14:28

Why do I have to do `rmmod kvm_intel` in 25.04 to use VirtualBox

1 Answers1