A recent development in the VirtualBox source tree introduces an early but usable KVM backend for Linux hosts. According to a comment by contributor Alexander Eichner, the new backend is now in a workable state, or at least when running modern guest operating systems. Older or more unusual guests, such as DOS, have not yet been tested.
And if you’re wondering what benefits this brings, the main one is that having a KVM backend allows VirtualBox to continue running virtual machines even when its own kernel modules (vboxdrv, vboxnetflt, vboxnetflt, vboxnetflt) cannot be loaded.
This is especially relevant on modern Linux systems, where Secure Boot, kernel hardening, or distribution-specific policies can block third-party kernel drivers. In such cases, VirtualBox will now automatically fall back to using KVM if it is available on the host system.
In addition, Eichner also notes that saved states should remain compatible between VirtualBox’s native hypervisor and the KVM backend, though this is subject to the usual caveat and has not yet been broadly validated.
At this stage, the KVM backend is not available in official test builds. Users interested in trying it must build VirtualBox directly from source. In other words, the feature remains experimental and is aimed primarily at developers and advanced users who are willing to compile and test development code.
Once it has been stabilized, it is expected to arrive in a future version of VirtualBox, but for now, there’s no additional information provided on which release it will be included in or when that might happen.
