til: fix virtualbox on kernel 6.12+

Author: foosel

content/til/how-to-fix-virtualbox-on-fedora38-with-kernel-6410.md content/til/how-to-fix-virtualbox-on-fedora-38-with-kernel-6410.md

@@ -5,6 +5,8 @@ tags:
 - linux
 - fedora
 - virtualbox
+aliases:
+- how-to-fix-virtualbox-on-fedora38-with-kernel-6410
 ---
 
 I recently did a software update on my laptop running Fedora 38, and that also brought in a kernel update. Starting my Win10 VirtualBox VM afterwards no longer worked as it needed the kernel module to be recompiled. However, that failed:

content/til/how-to-fix-virtualbox-on-fedora-40-with-kernel-612.md

@@ -0,0 +1,26 @@
+---
+title: "How to fix VirtualBox on Fedora 40 with Kernel 6.12+"
+date: 2025-02-27
+tags:
+- linux
+- fedora
+- virtualbox
+---
+
+I (accidentally[^1]) did a software update on my laptop last night, and this morning when I needed my Win10 VM for something, VirtualBox threw an error like this at me:
+
+> 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).
+
+A quick web search for "fedora update virtualbox vboxisomaker" gave me [this forum post](https://discussion.fedoraproject.org/t/139896) and consequently 
+[this bug report](https://www.virtualbox.org/ticket/22248), in which I found the solution: I just had to add the kernel parameter `kvm.enable_virt_at_load=0` to disable KVM - 
+which comes enabled by default since Kernel 6.12. I accomplished that with grubby:
+
+``` bash
+sudo grubby --update-kernel=ALL --args="kvm.enable_virt_at_load=0"
+```
+
+After a reboot, VirtualBox started again.
+
+Given how often VirtualBox breaks for me on updates, long term I think I really need to find a different solution... And yes, I also really need to upgrade to Fedora 41, I know 😉
+
+[^1]: I needed to a quick reboot before an online call and promptly forgot to uncheck "install updates" on the reboot dialog. Which made me be late on the call. Meh.