Re: [Xen-devel] how page faults are handled in paravirtualized xenguests?

[Daniel Stodden <stodden@xxxxxxxxxx>]

On Tue, 2008-03-11 at 17:28 +0100, Daniel Stodden wrote:
> yes. The ring1 kernel only works if you can play some tricks on virtual
> memory management in order to protect ring1 kernel memory from ring3
> user space (paging alone only distinguishes 0 from 1-3). On x86_32,

i should probably correct myself. wrong story, sorry. 

of course, paging distingushes ring 0-2 from 3. 

so 32-bit in 0/1/3 with segmentation protects xen from the kernel, and
32-bit paging then protects xen and the kernel from user mode. 

64-bit paging in 0/3/3 protects xen from both kernel and user mode, but
as i mentioned, you need a PT switch to keep the kernel safe. 

maybe more than you asked for :}

daniel

-- 
Daniel Stodden
LRR     -      Lehrstuhl für Rechnertechnik und Rechnerorganisation
Institut für Informatik der TU München             D-85748 Garching
http://www.lrr.in.tum.de/~stodden         mailto:stodden@xxxxxxxxxx
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