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,

ïi 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 fÃr Rechnertechnik und Rechnerorganisation
Institut fÃr Informatik der TU MÃnchen             D-85748 Garching
http://www.lrr.in.tum.de/~stodden         mailto:stodden@xxxxxxxxxx
PGP Fingerprint: F5A4 1575 4C56 E26A 0B33  3D80 457E 82AE B0D8 735B



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel