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xen-users
Re: [Xen-users] Dom0 Device Driver Access
> > On Tuesday June 17 2008 01:00:25 pm Artur Baruchi wrote:
> >> Does Dom0 access device driver using Ring Structures (like DomU does)
> >> or it has direct access to Device Driver (like Native Linux)?
> >
> > Yes and no. Things like memory management and paging are done by xen.gz.
> > Device access is (usually) done by dom0. xen.gz runs in ring 0; dom0 runs
> > in ring 1 (not sure about the domus); and userland runs in ring 3. A
> > quick search of xen.org couldn't provide a url to back this up.
>
> suggested reading:
> Xen and the Art of Virtualization
> www.cl.cam.ac.uk/research/srg/netos/papers/2003-xensosp.pdf
In this case I'd suggest also reading "Safe Hardware Access with the Xen
Virtual Machine Monitor":
http://www.cl.cam.ac.uk/research/srg/netos/papers/2004-oasis-ngio.pdf
The SOSP paper Todd suggests is an essential read if you want to understand
the technical aspects of Xen, particularly the PV memory management side of
things. But the version of Xen described in it uses a different IO model
that has dom0 talking to the hardware using paravirtual descriptor rings for
block and net - this is no longer the case.
The OASIS paper describes (roughly) the architecture currently used, with dom0
having direct access to hardware IO devices and then providing virtual
devices to other domains.
I'd say the OASIS paper probably contains the answers to Artur's original
question but you may need to read the SOSP paper to fully understand it!
Cheers,
Mark
--
Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)
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