From: wolff@zen.et.tudelft.nl (Rogier Wolff) Subject: Re: Linux and OS/2 Date: 2 Jan 1993 10:07:11 GMT
jem@sunSITE.unc.edu (Jonathan Magid) writes:
>In article <1992Dec30.174352.4550@gallant.apple.com> erwin#m#_mike.ast_-_tac_mail_server@msgate.corp.apple.com (Mike Erwin) writes:
>>
>>You can't run another whole operating system inside of another
>Try telling this to the VM people down the hall!
Both of you are right: A well designed processor CAN run a whole
new OS in a VM handled by another OS. However Intel F..ks up processor
design every once in a while, and makes this kind of "tricks" impossible.
(they screp up with about the same frequency that they bring out new
processors)
The "go into 32 bit mode" instruction is nicely protected. This would
enable a VM handler to start software emulating 32 bit mode extra bits.
However to do this you need an "invalid operation" fault every time the
inferior process tries to modify bits that modify the processor privelige.
Now this fault is simply "ignored" by the intel processors.
Roger
-- **** a 486 in V86 mode is like a VW buggy with a 6 litre V12 motor. **** EMail: wolff@duteca.et.tudelft.nl ** Tel +31-15-783644 or +31-15-142371