linux-kernel - Re: [PATCH v4.4-rc8 1/4] x86/microcode/intel: save_mc_for

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Date:	Wed, 9 Mar 2016 13:41:17 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	tim.gardner@...onical.com, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4.4-rc8 1/4] x86/microcode/intel: save_mc_for_early:
 Squelch frame size warning


* Borislav Petkov <bp@...en8.de> wrote:

> On Thu, Jan 07, 2016 at 07:59:56AM -0700, tim.gardner@...onical.com wrote:
> > From: Tim Gardner <tim.gardner@...onical.com>
> > 
> > arch/x86/kernel/cpu/microcode/intel.c: In function 'save_mc_for_early':
> > arch/x86/kernel/cpu/microcode/intel.c:516:1: warning: the frame size of 1032 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> Ok, so this looks like a 32-bit warning to me.
> 
> Hmm, so, on the one hand we do have:
> 
> $ git grep CONFIG_FRAME_WARN arch/x86/
> arch/x86/configs/i386_defconfig:291:CONFIG_FRAME_WARN=2048
> 
> which came in with:
> 
> 5cb04df8d3f0 ("x86: defconfig updates")
> 
> and OTOH:
> 
> config FRAME_WARN
>         int "Warn for stack frames larger than (needs gcc 4.4)"
>         range 0 8192
>         default 0 if KASAN
>         default 1024 if !64BIT
> 		^^^^
> 
>         default 2048 if 64BIT
>         help
>           Tell gcc to warn at build time for stack frames larger than this.
>           Setting this too low will cause a lot of warnings.
>           Setting it to 0 disables the warning.
>           Requires gcc 4.4
> 
> which is still 1024.
> 
> tip guys, maybe it is time to update lib/Kconfig.debug too?

I think we should rather update the 32-bit defconfig? 64-bit stacks are more 
generous, and a 2K stack footprint is pretty extreme on 32-bit I think ...

Thanks,

	Ingo