[Bug]: Linux host gets kernel panic (keyboard caps lock led blinking, black screen) when starting any vm

[jospezial]

Version

trunk/main

Host OS Type

Linux

Host OS name + version

Gentoo amd64

Host Architecture

x86

Guest OS Type

all

Guest Architecture

x86

Guest OS name + version

No response

Component

Host Support

What happened?

My Gentoo Linux host gets instantly kernel panic when starting any vm.
The screen goes black. Only a small rectangle of the right lower corner of my plasma desktop is visible
The keyboard caps lock led are blinking.
In this case I can only power off my PC.
There is no VBox.log after that. Only 2 and 3.
Nothing in /var/log/messages at crash time.

How can we reproduce this?

app-emulation/virtualbox-9999::gentoo was built with the following:
USE="alsa dbus gui nls opengl pam pulseaudio sdk sdl strip udev vmmraw -debug -dist-kernel -doc -dtrace -java -lvm -modules-compress -modules-sign (-pch) -python -test -vboxwebsrv -vde -vnc" ABI_X86="(64)" PYTHON_SINGLE_TARGET="python3_13 -python3_11 -python3_12 -python3_14"

My build from September 15th did not have this bug but when I built it on 26th it happend.
Linux jlgentoo 6.17.0 #1 SMP PREEMPT_DYNAMIC Mon Sep 29 11:09:17 CEST 2025 x86_64 AMD Athlon(tm) II X2 255 Processor AuthenticAMD GNU/Linux

Did you upload all of your necessary log files, screenshots, etc.?

• Yes, I've uploaded all pertinent files to this issue.

[galitsyn-oracle]

jospezial,

Which version of VirtualBox are you using? I suspect it has something to do with unloaded kvm_intel.ko (or AMD one in your case). Did you unload or blacklisted it?

[jospezial]

It was built from this git repo main.
Yes I did rmmod kvm-amd before starting.

[ramshven]

With VirtualBox 7.2.2, you no longer need to blacklist or remove kvm_intel/kvm_amd and kvm modules. VirtualBox will use KVM kernel API. So please try removing the blacklisted KVM modules and try starting VirtualBox VMs.

[galitsyn-oracle]

It was built from this git repo main.

Having git revision hash might be helpful to have though.

I think I also seen similar behavior here. Does it happen if you specify kvm.enable_virt_at_load=0 in kernel command line, then reboot host and keep kvm_XXX module running when starting a VM?

[galitsyn-oracle]

One more thing, if host is running kernel 6.16 and newer, removing kvm_XXX module would not be needed anymore.

[jospezial]

It works if I don't rmmod kvm-amd. Have not tested the other changes for now.
kvm 917504 2 kvm_amd,vboxdrv

[jospezial]

I think I also seen similar behavior here. Does it happen if you specify kvm.enable_virt_at_load=0 in kernel command line, then reboot host and keep kvm_XXX module running when starting a VM?

Does no change. The crash does not happen then.

[galitsyn-oracle]

I think I also seen similar behavior here. Does it happen if you specify kvm.enable_virt_at_load=0 in kernel command line, then reboot host and keep kvm_XXX module running when starting a VM?

Does no change. The crash does not happen then.

Thank you for confirmation.