[Lguest] lguest above lguest

[Rusty Russell]

On Mon, 20 Dec 2010 06:57:00 pm Eugene Kov wrote:
> 
> Hi all
> I'm asking myself a question that I'm not sure about the answer.Is it possible to run an
> lguest guest above a currently running lguest guest?

Unfortunately, we rely on the ring levels of the x86 architecture to provide
separation between userspace and kernel.  And between guest kernel and host.
In practice, the host kernel runs in ring 0, the guest kernel runs in ring 1
and the guest userspace runs in ring 3.

This means we have one ring level left.  So one level of nesting should be
possible, if slow.

To do more than one level, I believe that you may be able to run guest kernel
and userspace at the same ring level using remapping in the host.  That would
be harder, and mapping and unmapping the kernel memory on every system call
entry is going to be slow...

Cheers,
Rusty.