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Re: [Xen-devel] Uses of &frame_table[xfn]

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Subject: Re: [Xen-devel] Uses of &frame_table[xfn]
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Mon, 2 Jan 2006 19:22:24 +0000
Cc: "Magenheimer, Dan \(HP Labs Fort Collins\)" <dan.magenheimer@xxxxxx>, "Cihula, Joseph" <joseph.cihula@xxxxxxxxx>
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> > But a better question, especially as we move forward with dom0
> > disagregation and privilege reduction, is what do you want to do based
> > on this information?
> You are correct that I was asking the wrong question.
> What I want to ask is:  How do I determine if this is
> a domain that is running a backend driver and has access
> to physical devices?  On Xen/ia64 right now, that is the
> same question, but it will be different in the future.

Well that's an interesting question...

We used to also have SIF flags to tell domains if they were supposed to run a 
backend.  This was due to the way the control message protocol worked at the 
time, and is no longer necessary.  Now we just have SIF_INITDOMAIN (you're 
dom0 - grab the console, etc!) and SIF_PRIVILEGED (you're just privileged).

In general, though, I'm not sure you'll want / need to a flag that says "this 
is a driver domain".  Domains that have access to real physical devices will 
just see them on the bus when they probe - non driver domains just won't see 
any physical devices.  Backend drivers, as always, will just plumb virtual 
devices through to other devices available in the system (which may just 
happen to be physical devices).

Basically, I'm saying that "driver domain" is not a special capability from 
the PoV of the guest.  Does this satisfy your query, or do you have something 
in mind that explicitly requires such a flag?


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