[off-topic] Fully virtualisable CPUs

S. Lee (sl14@crux5.cit.cornell.edu)
5 Sep 1996 22:16:32 GMT

In article <m0uy2nV-0005FbC@lightning.swansea.linux.org.uk>,
Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
>> Is it possible to fool instructions like LAR so we could convince a
>> program in user mode that it was running in kernel mode?
>Nope. Motorola got this 100% right on the 680x0 series processors, Intels
>x86 processors are not virtualisable, they just have a cute virtual 8086

Sorry about being off-topic, but what makes a CPU fully virtualisable
(that it can run several OSes in different VMs)? And what make the x86
not so? Is there any improvement in the latter x86 CPUs (Pentium, PPro)
that makes virtualising easier?