Re: [off-topic] Fully virtualisable CPUs
08 Sep 1996 01:42:50 -0400

Alan Cox <> writes:

> On the intel chips instructions that report the CPU state don't cause
> an exception. Pity as if they did we could conceivably just boot windows95
> or nt or OS/2 or whatever in a window (and vice versa).

> Alan

It seems to me trivial to have a little virtualisable module which
simply picked up an instruction, examined it for whether it was trying
to get a report on CPU state, and then recoded the instructions to do
the CPU state manually, and at the end of the code piece jump back
into the little just-in-time-interpreting-reassembler for the next

Yeah it would run slow the first few times a process ran, but it would
leave a long trail of compiled piecelets, and without too much
difficulty that could be cached on disk along with the executable so
that next time the executable was run the loader would load the
cache'd interpreted reassembled progress. In this way, one could even
boot a new version of Linux in a Linux window, or FreeBSD, or NT, or
Windows '95, or ... CP/M :) or Solaris 'x86 ... Heck I can do this
myself. Anybody have references on:

* x86 instruction set

on the Internet someplace I could borrow?

I could just use the FreeBSD boot disk as a testbed ...