I can confirm Virtualbox 5.2 from virtualbox.org also works with linux-hwe 4.13.0-29.32~16.04.1 from ppa:canonical-kernel-team/pti which fixes Spectre with IBRS/IBPB.
And I hope Virtualbox implements IBRS/IBPB path through to also allow Spectre protection in vms.
I can confirm Virtualbox 5.2 from virtualbox.org also works with linux-hwe 4.13.0- 29.32~16. 04.1 from ppa:canonical- kernel- team/pti which fixes Spectre with IBRS/IBPB.
And I hope Virtualbox implements IBRS/IBPB path through to also allow Spectre protection in vms.