linux-kernel - Re: [PATCH v4] MIPS: adding a safety check for cpu_has

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Date:   Wed, 4 May 2022 22:28:22 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Stephen Zhang <starzhangzsd@...il.com>
Cc:     macro@...am.me.uk, liam.howlett@...cle.com, geert@...ux-m68k.org,
        ebiederm@...ssion.com, dbueso@...e.de, alobakin@...me,
        f.fainelli@...il.com, paul@...pouillou.net, linux@...ck-us.net,
        anemo@....ocn.ne.jp, zhangshida@...inos.cn,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org
Subject: Re: [PATCH v4] MIPS: adding a safety check for cpu_has_fpu

On Mon, May 02, 2022 at 11:20:02AM +0800, Stephen Zhang wrote:
> From: Shida Zhang <zhangshida@...inos.cn>
> 
> There is a chance 'cpu_has_fpu' would still be overridden when the
> CONFIG_MIPS_FP_SUPPORT configuration option has been disabled. So
> add a safety check for 'cpu_has_fpu'.
> 
> Suggested-by: Maciej W. Rozycki <macro@...am.me.uk>
> Signed-off-by: Shida Zhang <zhangshida@...inos.cn>
> ---
>  Changelog in v1 -> v2:
>  - Choose to redefine cpu_has_fpu to solve the problem silently.
> 
>  Changelog in v2 -> v3:
>  - Choose to point out the error instead.
> 
>  Changelog in v3 -> v4:
>  - Make the check work for 'nofpu' option.
> 
>  arch/mips/include/asm/cpu-features.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/mips/include/asm/cpu-features.h b/arch/mips/include/asm/cpu-features.h
> index de8cb2ccb781..c0983130a44c 100644
> --- a/arch/mips/include/asm/cpu-features.h
> +++ b/arch/mips/include/asm/cpu-features.h
> @@ -133,6 +133,9 @@
>  #  define raw_cpu_has_fpu	0
>  # endif
>  #else
> +# if cpu_has_fpu
> +#  error "Forcing `cpu_has_fpu' to non-zero is not supported"
> +# endif
>  # define raw_cpu_has_fpu	cpu_has_fpu
>  #endif
>  #ifndef cpu_has_32fpr
> -- 
> 2.30.2

applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]