linux-kernel - Re: [PATCH] x86: Disable CONFIG_X86_DECODER

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Message-Id: <20140211110117.3da57b1728c80ad2af6baeab@canb.auug.org.au>
Date:	Tue, 11 Feb 2014 11:01:17 +1100
From:	Stephen Rothwell <sfr@...b.auug.org.au>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
	Richard Weinberger <richard@....at>,
	Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH] x86: Disable CONFIG_X86_DECODER_SELFTEST in
 allmod/allyesconfigs

Hi Ingo,

On Wed, 5 Feb 2014 06:51:37 +0100 Ingo Molnar <mingo@...nel.org> wrote:
>
> 
> * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
> > > BTW you probably also want to do the same for the x86 instruction 
> > > decoder test. It seems to be the biggest compile time waster in 
> > > allyesconfig and I usually disable it too.
> > 
> > Agreed, that should be disabled too by default. Although in that 
> > case I think the COMPILE_TEST combination makes more sense, since 
> > it's a coverage issue.
> 
> I'd say randconfig will cover it often enough, and the failure is also 
> borderline build coverage related: you cannot really make the decoder 
> test fail via source level changes, only with changes in the build 
> environment, so I agree with Andi that we can disable this one too - 
> via the patch below.
> 
> Thanks,
> 
> 	Ingo
> 
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> 
> diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
> index 0f3621e..f0fca39 100644
> --- a/arch/x86/Kconfig.debug
> +++ b/arch/x86/Kconfig.debug
> @@ -184,6 +184,11 @@ config HAVE_MMIOTRACE_SUPPORT
>  config X86_DECODER_SELFTEST
>  	bool "x86 instruction decoder selftest"
>  	depends on DEBUG_KERNEL && KPROBES
> +	#
> +	# It can take some time to validate the image,
> +	# make sure {allyes|allmod}config doesn't enable it:
> +	#
> +	depends on !COMPILE_TEST
>  	---help---
>  	 Perform x86 instruction decoder selftests at build time.
>  	 This option is useful for checking the sanity of x86 instruction

When this got applied to the tip tree, Linus had already applied an
earlier version as commit f8f202348208, and this one (commit
8c778d541bec) now duplicates the actual dependency in !COMPILE_TEST (but
does add a useful comment) ...

-- 
Cheers,
Stephen Rothwell <sfr@...b.auug.org.au>

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