linux-kernel - Re: [PATCH] x86/resctrl: Annotate __get_mem_config_intel() as _

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Message-ID: <fc49e252-6283-4a37-b4e8-bd329f326e68@intel.com>
Date: Thu, 12 Sep 2024 15:33:09 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Nathan Chancellor <nathan@...nel.org>, Fenghua Yu <fenghua.yu@...el.com>,
	<x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar
	<mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
	<dave.hansen@...ux.intel.com>
CC: <linux-kernel@...r.kernel.org>, <llvm@...ts.linux.dev>,
	<patches@...ts.linux.dev>
Subject: Re: [PATCH] x86/resctrl: Annotate __get_mem_config_intel() as __init

Hi Nathan,

Apologies for the delay.

On 8/22/24 5:12 PM, Nathan Chancellor wrote:
> After a recent LLVM change [1] that deduces __cold on functions that
> only call cold code (such as __init functions), there is a section
> mismatch warning from __get_mem_config_intel(), which got moved to
> .text.unlikely. as a result of that optimization:
> 
>    WARNING: modpost: vmlinux: section mismatch in reference: __get_mem_config_intel+0x77 (section: .text.unlikely.) -> thread_throttle_mode_init (section: .init.text)
> 
> Mark __get_mem_config_intel() as __init as well since it is only called
> from __init code, which clears up the warning.

It looks to me as though __rdt_get_mem_config_amd() may need the same __init
treatment and it is not clear to me why __get_mem_config_intel() would trigger
such warning, but not __rdt_get_mem_config_amd()?

> 
> Link: https://github.com/llvm/llvm-project/commit/6b11573b8c5e3d36beee099dbe7347c2a007bf53 [1]
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
>   arch/x86/kernel/cpu/resctrl/core.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 1930fce9dfe9..b28646f1d9d6 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -199,7 +199,7 @@ static inline bool rdt_get_mb_table(struct rdt_resource *r)
>   	return false;
>   }
>   
> -static bool __get_mem_config_intel(struct rdt_resource *r)
> +static bool __init __get_mem_config_intel(struct rdt_resource *r)

Surely resctrl is not consistent in this regard but I understand from the coding style
doc that storage class should precede the return type, so perhaps:
	static __init bool __get_mem_config_intel(struct rdt_resource *r)

We may need to follow this recommended style for this to be included.

>   {
>   	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
>   	union cpuid_0x10_3_eax eax;
> 
> ---
> base-commit: 7424fc6b86c8980a87169e005f5cd4438d18efe6
> change-id: 20240822-x86-restctrl-get_mem_config_intel-init-3af02a5130ba
> 
> Best regards,

Thank you very much.

Reinette