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

From: Ingo Molnar <mingo@kernel.org>
To: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	Andy Lutomirski <luto@kernel.org>, Nadav Amit <namit@vmware.com>,
	Brian Gerst <brgerst@gmail.com>,
	Denys Vlasenko <dvlasenk@redhat.com>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH 4/4] x86/percpu: Use C for percpu read/write accessors
Date: Mon, 9 Oct 2023 13:41:29 +0200	[thread overview]
Message-ID: <ZSPm6Z/lTK1ZlO8m@gmail.com> (raw)
In-Reply-To: <CAFULd4Z3C771u8Y==8h6hi=mhGmy=7RJRAEBGfNZ0SmynxF41g@mail.gmail.com>

* Uros Bizjak <ubizjak@gmail.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