linux-kernel - Re: [PATCH] x86/microcode: Do not select FW

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Message-ID: <20200610081609.GA14118@zn.tnic>
Date:   Wed, 10 Jun 2020 10:16:09 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        x86-ml <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] x86/microcode: Do not select FW_LOADER

On Wed, Jun 10, 2020 at 02:29:11PM +1000, Herbert Xu wrote:
> The x86 microcode support works just fine without FW_LOADER.  In
> fact these days most people load them early in boot so FW_LOADER
> never gets into the picture anyway.

What's the use case here?

$ git grep -E "select.*FW_LOADER" | wc -l
132

so this thing gets selected anyway, practically.

Also, I'm working on removing that homegrown get_builtin_firmware() and
use the one in the fw loader:

https://lkml.kernel.org/r/20200408094526.GC24663@zn.tnic

Leaving in the rest for reference.

> People who need the FW_LOADER capability can still enable it.
> 
> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 1d6104ea8af0..8aac7a65bfbb 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1296,7 +1296,6 @@ config MICROCODE
>  	bool "CPU microcode loading support"
>  	default y
>  	depends on CPU_SUP_AMD || CPU_SUP_INTEL
> -	select FW_LOADER
>  	---help---
>  	  If you say Y here, you will be able to update the microcode on
>  	  Intel and AMD processors. The Intel support is for the IA32 family,
> @@ -1318,7 +1317,6 @@ config MICROCODE_INTEL
>  	bool "Intel microcode loading support"
>  	depends on MICROCODE
>  	default MICROCODE
> -	select FW_LOADER
>  	---help---
>  	  This options enables microcode patch loading support for Intel
>  	  processors.
> @@ -1330,7 +1328,6 @@ config MICROCODE_INTEL
>  config MICROCODE_AMD
>  	bool "AMD microcode loading support"
>  	depends on MICROCODE
> -	select FW_LOADER
>  	---help---
>  	  If you select this option, microcode patch loading support for AMD
>  	  processors will be enabled.
> diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
> index 7019d4b2df0c..5524ea15b3df 100644
> --- a/arch/x86/kernel/cpu/microcode/core.c
> +++ b/arch/x86/kernel/cpu/microcode/core.c
> @@ -145,7 +145,6 @@ extern struct builtin_fw __end_builtin_fw[];
>  
>  bool get_builtin_firmware(struct cpio_data *cd, const char *name)
>  {
> -#ifdef CONFIG_FW_LOADER
>  	struct builtin_fw *b_fw;
>  
>  	for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++) {
> @@ -155,7 +154,6 @@ bool get_builtin_firmware(struct cpio_data *cd, const char *name)
>  			return true;
>  		}
>  	}
> -#endif
>  	return false;
>  }
>  
> -- 
> Email: Herbert Xu <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

-- 
Regards/Gruss,
    Boris.

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