Yes, VirtualBox will use hardware virtualization if the host CPU supports it and it is available (i.e. not already used by something else). Whether the host OS has some built-in virtualization capabilities or not doesn't matter (with the caveat that the host OS may be taking over the hardware virtualization and then nothing else can use it).TSU wrote:Because VBox possesses its own "virtualization interface code" independent of the OS,
Will this mean that if I run a HostOS which <does not> support any hypervisor but have the CPU virt extensions enabled in the BIOS, that Virtualbox will still be able to support hardware assisted virtualization and with 5.x also present a paravirtualization interface of choice to the Guest?
(Key here is that the OS specifically does not support virtualization so VBox essentially bypasses any OS non-support).
Yes, VirtualBox can present a paravirtualization interface to the guest regardless of what the host OS can or can't do. Hyper-V for Windows guest on OS X or KVM for Linux hosts on Windows is no problem.
The paravirtualization interfaces in fact do not require hardware virtualization, there two are more or less orthogonal. A lot of the paravirtualization machinery was originally designed to improve virtualization performance on systems with no hardware virtualization. The interfaces are still useful but sometimes not as critical.