linux-kernel - Re: [patch] paravirt: isolate module ops

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Message-Id: <1168132196.20372.45.camel@localhost.localdomain>
Date:	Sun, 07 Jan 2007 12:09:56 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Zachary Amsden <zach@...are.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Jeremy Fitzhardinge <jeremy@...source.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>,
	Adrian Bunk <bunk@...sta.de>
Subject: Re: [patch] paravirt: isolate module ops

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.

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