linux-kernel - Re: [PATCH 1/1] Speedfreq-SMI call clobbers ECX

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Date:	Thu, 6 Mar 2008 09:38:19 +0100
From:	Stephan Diestelhorst <langer_mann@....de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	davej@...emonkey.org.uk, cpufreq@...ts.linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] Speedfreq-SMI call clobbers ECX

On, March 5th 2008 16:35:20 Ingo Molnar wrote:
> * Stephan Diestelhorst <langer_mann@....de> wrote:
> > @@ -184,7 +184,7 @@ static void speedstep_set_state (unsigne
> >  		__asm__ __volatile__(
> >  			"movl $0, %%edi\n"
> >  			"out %%al, (%%dx)\n"
> > -			: "=b" (new_state), "=D" (result)
> > +			: "=b" (new_state), "=D" (result), "=c" (ecx_clobber)
> >
> >  			: "a" (command), "b" (function), "c" (state), "d" (smi_port),
> >  			: "S" (0)
> >
> >  			);
>
> stupid suggestion: why not do a pusha/popa around those
> instructions, to make sure everything is restored? This isnt a
> fastpath and being conservative about SMI side-effects cannot hurt

That sounds like a sane thing to do to me. Should I provide a 'patch'? 
Or leave that (and the decision about it) to the maintainer?

Regards,
  Stephan
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