specify supported kernel version
Please specify on VirtualBox web site (link to supported kernels wiki article, e.g. https://www.virtualbox.org/wiki/Supported-kernel-versions could be available at https://www.virtualbox.org/wiki/Downloads) the supported host and guest kernel versions. This applies especially for Linux but also for Solaris and other free UNIX-like operating systems where users can install own version of the kernel. It is always hard to determine whether the current stable and also development version of VirtualBox support the latest stable version or possibly RC of Linux kernel - same applies for other free UNIX'es as well. This applies especially to host but also guest - in both situation the mentioned questions appears. This could be just like:
Linux host: supported kernel version up to 4.12.10
Solaris host: ...
... like by which VirtualBox version supports up to which kernel version in host.