linux-kernel - Re: [PATCH v6 05/12] x86/alternative: support ALTERNATIVE

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Date:   Wed, 10 Mar 2021 15:27:54 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Juergen Gross <jgross@...e.com>
Cc:     xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v6 05/12] x86/alternative: support ALTERNATIVE_TERNARY

On Tue, Mar 09, 2021 at 02:48:06PM +0100, Juergen Gross wrote:
> diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
> index 89889618ae01..4fb844e29d26 100644
> --- a/arch/x86/include/asm/alternative.h
> +++ b/arch/x86/include/asm/alternative.h
> @@ -178,6 +178,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
>  	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
>  	".popsection\n"
>  
> +#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2)	\
> +	ALTERNATIVE_2(oldinstr, newinstr2, X86_FEATURE_ALWAYS, newinstr1, feature)

Make that:

/*
 * If @feature is set, patch @newinstr_yes, else @newinstr_no
 */
#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
        ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, newinstr_yes, feature)

and in alternative-asm.h too pls.

Regardless, this looks nice! :)

Thx.

-- 
Regards/Gruss,
    Boris.

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