linux-kernel - Re: [PATCH v2 10/11] x86/alternatives: Simplify ALTERNATIVE

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Message-ID: <20230915074647.GA6721@noisy.programming.kicks-ass.net>
Date:   Fri, 15 Sep 2023 09:46:47 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, David.Kaplan@....com,
        Andrew.Cooper3@...rix.com, jpoimboe@...nel.org,
        gregkh@...uxfoundation.org, nik.borisov@...e.com
Subject: Re: [PATCH v2 10/11] x86/alternatives: Simplify ALTERNATIVE_n()

On Wed, Sep 13, 2023 at 04:38:47PM +0200, Borislav Petkov wrote:

>   [ bp: Make labels unique and thus all sizing use unambiguous labels.
>     Add more info. ]

> +#define __ALTERNATIVE(oldinstr, newinstr, ft_flags, n)			\
> +	OLDINSTR(oldinstr, n)						\
> +	ALTINSTR_ENTRY(ft_flags)					\
> +	ALTINSTR_REPLACEMENT(newinstr)

> +#define ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2)	\
> +	__ALTERNATIVE(ALTERNATIVE(oldinst, newinst1, flag1),		\
> +		    newinst2, flag2, 1)

> +#define ALTERNATIVE_3(oldinst, newinst1, flag1, newinst2, flag2,	\
> +		      newinst3, flag3)					\
> +	__ALTERNATIVE(ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2), \
> +		    newinst3, flag3, 2)


So I see what you did with that @n argument, but urgh, do we really need
this? I mean, it just makes things harder to use and it doesn't actually
fix anything.. :/