WIP

This initial draft enters vmx non-root operation and exits.
It does the required vmxon and vmcs setup. It only works on uniproc
hosts for now. We should disable interrupts during vmx non-root operation
or they will not be passed to the host, even tho they produce vm exits.
In a later iteration we will do host interrupt emulation.

When the first draft is complete we will properly document it and explain
in more detail and in an orderly manner what we're trying to accomplish,
basically we're trying to write a hypervisor in several iterations,
each one incrementally building on the previous one.

The steps will be properly documented, for now the next step is to be
able for a thread to re-enter on a vmcs, it should the same thread that first run it.

Later, we should make sure runs on smp host, following should be done:
 - Allocate a VMXON region for each logical processor.
 - Migrate the VMCS to the VMXON of a different logical processor before
 reentering in case the scheduler has run the thread on a different LP.
 - Disable preemption from the point where we start writting host state
   into the state area up until vm exit, since if the kernel is preempted
   in the middle of writting host-state area and some of the
   state is LP-dependent (it is, like the TSR) we can corrupt the host on exit.

After that, the next phase should implement host-interrupt passthrough (kvm calls it emulation),
since when a host interrupt happens, it produces a vm exit and it is our responsibility
to call the host interrupt handling code.

Later, we should virtualize guest memory using EPT, for now the guest has
paging disabled and sees the host physical memory directly.