While following the tutorial on How to install OS X Mountain Lion in Virtualbox with iAtkos from the good folks of MacBraker I came accross the error “VT-x locked or unavailable in MSR“, which was totally new for me. Heck, I even didn’t know that it was supposed to mean.
It turns out that VT-x is a virtualization techology created by Intel to allow the, well, virtualization of other software, and 64 bits systems require it. It must be supported by the processor, and unless you have a very old computer, the odds are that you already have support for it. It may be just disabled.
VT-x usually (always?) come disabled, so it is necessary enable it in the BIOS of your computer. Restart it, press the key to enter BIOS setup (mine was F2, sometimes it is F10 or even DEL), and search there for “VT”, “VT-x”, “Virtualization Technology” (which was my case) or something like that.
Turn it on and POWER OFF your computer – a simple restart is not enough. Pull the energy cord off. Done that, your VirtualBox image should work fine now.