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Subject: Re: [patch] paravirt: isolate module ops
From: Rusty Russell <rusty@rustcorp.com.au>
To: Zachary Amsden <zach@vmware.com>
Cc: Ingo Molnar <mingo@elte.hu>, Jeremy Fitzhardinge <jeremy@xensource.com>,
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       linux-kernel@vger.kernel.org, Arjan van de Ven <arjan@infradead.org>,
       Adrian Bunk <bunk@stusta.de>
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Date: Sun, 07 Jan 2007 12:09:56 +1100
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On Sat, 2007-01-06 at 12:55 -0800, Zachary Amsden wrote:
> Rusty Russell wrote:
> >
> > +int paravirt_write_msr(unsigned int msr, u64 val);
> 
> If binary modules using debug registers makes us nervous, the 
> reprogramming MSRs is also similarly bad.

Yes, but this is simply from experience.  Several modules wrote msrs
(you can take out the EXPORT_SYMBOL and find them quite quickly).

> > +void raw_safe_halt(void);
> > +void halt(void);
> 
> These shouldn't be done by modules, ever.  Only the scheduler should 
> decide to halt.

Several modules implement alternate halt loops.  I guess being in a
module for specific CPUs makes sense...

Cheers!
Rusty.