linux-kernel - Re: [PATCH 01/10] x86: add support for multiple choice alternatives

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Date:	Wed, 17 Feb 2010 14:47:29 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Luca Barbieri <luca@...a-barbieri.com>
CC:	mingo@...e.hu, hpa@...or.com, a.p.zijlstra@...llo.nl,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/10] x86: add support for multiple choice alternatives

On 02/17/2010 01:42 PM, Luca Barbieri wrote:
> This patch modifies the x86 alternative macros to allow more than one
> alternative code sequence.
>
> This is done by simply adding multiple alternative patches, which are
> applied in sequence, overwriting previous ones.
>
> +/* alternative assembly primitive: */
> +#define ALTERNATIVE(oldinstr, newinstr, feature)			\
> +      "661:\n\t" oldinstr "\n662:\n"					\
> +      ALTERNATIVE_PATCH("661b", "662b", newinstr, feature)
> +
> +#define ALTERNATIVE3(oldinstr, newinstr1, feature1, newinstr2, feature2)			\
> +      "661:\n\t" oldinstr "\n662:\n"					\
> +      ALTERNATIVE_PATCH("661b", "662b", newinstr1, feature1) "\n" \
> +      ALTERNATIVE_PATCH("661b", "662b", newinstr2, feature2)
> +
> +#define ALTERNATIVE4(oldinstr, newinstr1, feature1, newinstr2, feature2, newinstr3, feature3)			\
> +      "661:\n\t" oldinstr "\n662:\n"					\
> +      ALTERNATIVE_PATCH("661b", "662b", newinstr1, feature1) "\n" \
> +      ALTERNATIVE_PATCH("661b", "662b", newinstr2, feature2) "\n" \
> +      ALTERNATIVE_PATCH("661b", "662b", newinstr3, feature3)
> +
>    

Suggest documenting the precedence of alternatives: if both feature1 and 
feature2 are present, which newinstr is patched in?

-- 
error compiling committee.c: too many arguments to function

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