linux-kernel - Re: [PATCH] x86/Kconfig: make X86

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Date:   Mon, 9 Mar 2020 21:36:32 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tony W Wang-oc <TonyWWang-oc@...oxin.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        DavidWang@...oxin.com, CooperYan@...oxin.com,
        QiyuanWang@...oxin.com, HerryYang@...oxin.com, CobeChen@...oxin.com
Subject: Re: [PATCH] x86/Kconfig: make X86_UMIP to cover any X86 CPU

On Mon, Mar 09, 2020 at 02:06:30PM +0800, Tony W Wang-oc wrote:
> While the UMIP (User-Mode Instruction Prevention) is a generic X86 CPU
> feature, there is no need to tie X86_UMIP only to Intel and AMD.

It is not generic - it just lost the "INTEL" in its name.

> So remove that dependency from the Kconfig rules.
> 
> Signed-off-by: Tony W Wang-oc <TonyWWang-oc@...oxin.com>
> ---
>  arch/x86/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 5ad3957..ca16b762 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1871,7 +1871,6 @@ config X86_SMAP
>  
>  config X86_UMIP
>  	def_bool y
> -	depends on CPU_SUP_INTEL || CPU_SUP_AMD
>  	prompt "User Mode Instruction Prevention" if EXPERT
>  	---help---
>  	  User Mode Instruction Prevention (UMIP) is a security feature in
> -- 

If you're going to do that, is there even any use for that config option
at all?

AFAICT, it adds ~1K to kernel text so we might just as well remove the
ifdeffery completely. The code ends up built in in 99% of the cases
anyway...

-- 
Regards/Gruss,
    Boris.

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