linux-kernel - Re: [PATCH] x86: Fix amd_check

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Date:   Tue, 25 Jul 2023 11:20:46 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Arnd Bergmann <arnd@...db.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Kees Cook <keescook@...omium.org>,
        Kim Phillips <kim.phillips@....com>,
        Alexey Kardashevskiy <aik@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Fix amd_check_microcode() declaration

On Tue, Jul 25, 2023 at 10:26:13AM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> The newly added amd_check_microcode() function has two conflicting definitions
> if CONFIG_CPU_SUP_AMD is enabled and CONFIG_MICROCODE_AMD is disabled. Since
> the header with the stub definition is not included in cpu/amd.c, this only
> causes a -Wmissing-prototype warning with W=1

Can we please promote -Wmissing-prototype to default or is it too noisy
yet?

> diff --git a/arch/x86/include/asm/microcode_amd.h b/arch/x86/include/asm/microcode_amd.h
> index 9675c621c1ca4..6a860d40b0411 100644
> --- a/arch/x86/include/asm/microcode_amd.h
> +++ b/arch/x86/include/asm/microcode_amd.h
> @@ -48,13 +48,18 @@ extern void __init load_ucode_amd_bsp(unsigned int family);
>  extern void load_ucode_amd_ap(unsigned int family);
>  extern int __init save_microcode_in_initrd_amd(unsigned int family);
>  void reload_ucode_amd(unsigned int cpu);
> -extern void amd_check_microcode(void);
>  #else
>  static inline void __init load_ucode_amd_bsp(unsigned int family) {}
>  static inline void load_ucode_amd_ap(unsigned int family) {}
>  static inline int __init
>  save_microcode_in_initrd_amd(unsigned int family) { return -EINVAL; }
>  static inline void reload_ucode_amd(unsigned int cpu) {}
> +#endif
> +
> +#ifdef CONFIG_CPU_SUP_AMD
> +extern void amd_check_microcode(void);
> +#else
>  static inline void amd_check_microcode(void) {}
>  #endif
> +
>  #endif /* _ASM_X86_MICROCODE_AMD_H */

Considering how cpu/amd.c provides the function implementation, that
header gunk should not be in microcode_amd.h but in ...asm/processor.h,
I'd say.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette