x86 protection rings
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From: David Hopwood on 27 Sep 2006 16:30 ammonton(a)cc.full.stop.helsinki.fi wrote: > In a related question, has any x86 OS used all the protection levels, or > are only ring 0 and ring 3 used? Virtual machine monitors (e.g. VMWare and Xen) sometimes use ring 1 to run the kernel code of a guest OS. That's the only software I'm aware of that uses ring 1 or 2. -- David Hopwood <david.nospam.hopwood(a)blueyonder.co.uk>
From: Jeff Kenton on 30 Sep 2006 11:13
David Hopwood wrote: > ammonton(a)cc.full.stop.helsinki.fi wrote: >> In a related question, has any x86 OS used all the protection levels, or >> are only ring 0 and ring 3 used? > > Virtual machine monitors (e.g. VMWare and Xen) sometimes use ring 1 to run > the kernel code of a guest OS. That's the only software I'm aware of that > uses ring 1 or 2. > Yes -- but this will go away when we they switch to using Intel virtualization facilities. |