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

[H. Peter Anvin]

Ingo Molnar wrote:
> * Stephan Diestelhorst <langer_mann@xxxxxx> 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 ...

You can't pusha/popa if you expect a result.  You can, of course, push 
and pop individual registers.

It's also kind of odd to do "movl $0,%%edi" instead of just setting EDI 
as an input.

	-hpa
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