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

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Date:	Tue, 11 Feb 2014 08:14:51 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Stephen Rothwell <sfr@...b.auug.org.au>
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


* Stephen Rothwell <sfr@...b.auug.org.au> wrote:

> 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) ...

Ok, I've zapped it from x86/urgent, thanks for letting me know!

	Ingo
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