Re: [PATCH] x86/build: Move '-mindirect-branch-cs-prefix' out of GCC-only block

From: Peter Zijlstra <peterz@infradead.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, Nick Desaulniers <ndesaulniers@google.com>,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH] x86/build: Move '-mindirect-branch-cs-prefix' out of GCC-only block
Date: Thu, 18 Aug 2022 09:49:01 +0200	[thread overview]
Message-ID: <Yv3u7XobZs/uPf6n@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20220817185410.1174782-1-nathan@kernel.org>

On Wed, Aug 17, 2022 at 11:54:11AM -0700, Nathan Chancellor wrote:
> LLVM 16 will have support for this flag so move it out of the GCC-only
> block to allow LLVM builds to take advantage of it.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1665
> Link: https://github.com/llvm/llvm-project/commit/6f867f9102838ebe314c1f3661fdf95700386e5a
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

> ---
> 
> I was not sure if this information is relevant for the commit message
> but I can boot without any issues on my test machines (two Intel and one
> AMD).
> 
>  arch/x86/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 7854685c5f25..987da87c7778 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -14,13 +14,13 @@ endif
>  
>  ifdef CONFIG_CC_IS_GCC
>  RETPOLINE_CFLAGS	:= $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register)
> -RETPOLINE_CFLAGS	+= $(call cc-option,-mindirect-branch-cs-prefix)
>  RETPOLINE_VDSO_CFLAGS	:= $(call cc-option,-mindirect-branch=thunk-inline -mindirect-branch-register)
>  endif
>  ifdef CONFIG_CC_IS_CLANG
>  RETPOLINE_CFLAGS	:= -mretpoline-external-thunk
>  RETPOLINE_VDSO_CFLAGS	:= -mretpoline
>  endif
> +RETPOLINE_CFLAGS	+= $(call cc-option,-mindirect-branch-cs-prefix)

Thanks for using the same option!