linux-kernel - Re: [PATCH 4/4] x86/percpu: Use C for percpu read/write accessors

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Message-ID: <ZSPm6Z/lTK1ZlO8m@gmail.com>
Date:   Mon, 9 Oct 2023 13:41:29 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Uros Bizjak <ubizjak@...il.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
        Nadav Amit <namit@...are.com>, Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH 4/4] x86/percpu: Use C for percpu read/write accessors


* Uros Bizjak <ubizjak@...il.com> wrote:

> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index ecb256954351..1edf4a5b93ca 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2393,7 +2393,7 @@ config CC_HAS_NAMED_AS
>  
>  config USE_X86_SEG_SUPPORT
>  	def_bool y
> -	depends on CC_HAS_NAMED_AS && SMP
> +	depends on CC_HAS_NAMED_AS && SMP && !KASAN
> +	depends on CC_HAS_NAMED_AS && SMP && !KASAN

So I'd rather express this as a Kconfig quirk line, and explain each quirk.

Something like:

	depends on CC_HAS_NAMED_AS
	depends on SMP
	#
	# -fsanitize=kernel-address (KASAN) is at the moment incompatible
	# with named address spaces - see GCC bug #12345.
	#
	depends on !KASAN

... or so.

BTW., please also document the reason why !SMP is excluded.

Thanks,

	Ingo