linux-kernel - Re: [PATCH v2 2/2] x86: Support compiling out human-friendly processor feature names

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Date:	Sat, 22 Feb 2014 13:36:40 -0800
From:	Josh Triplett <josh@...htriplett.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Borislav Petkov <bp@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Feng Tang <feng.tang@...el.com>,
	Ingo Molnar <mingo@...hat.com>,
	Jacob Shin <jacob.shin@....com>,
	Jan Beulich <JBeulich@...e.com>,
	Jussi Kivilinna <jussi.kivilinna@....fi>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Rob Landley <rob@...dley.net>,
	Seiji Aguchi <seiji.aguchi@....com>,
	Stephane Eranian <eranian@...gle.com>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v2 2/2] x86: Support compiling out human-friendly
 processor feature names

On Sat, Feb 22, 2014 at 01:18:14PM -0800, H. Peter Anvin wrote:
> On February 22, 2014 1:00:39 PM PST, Josh Triplett <josh@...htriplett.org> wrote:
> >On Sat, Feb 22, 2014 at 09:49:36PM +0100, Borislav Petkov wrote:
> >> On Sat, Feb 22, 2014 at 11:57:10AM -0800, Josh Triplett wrote:
> >> > diff --git a/arch/x86/boot/cpu.c b/arch/x86/boot/cpu.c
> >> > index 6ec6bb6..29207f6 100644
> >> > --- a/arch/x86/boot/cpu.c
> >> > +++ b/arch/x86/boot/cpu.c
> >> > @@ -16,7 +16,9 @@
> >> >   */
> >> >  
> >> >  #include "boot.h"
> >> > +#ifdef CONFIG_X86_FEATURE_NAMES
> >> >  #include "cpustr.h"
> >> > +#endif
> >> 
> >> You probably could get rid of this ifdef too by moving it into
> >cpustr.h
> >> after teaching arch/x86/boot/mkcpustr.c to issue it...
> >
> >That would require building and running mkcpustr, which doesn't happen
> >when !CONFIG_X86_FEATURE_NAMES.  (And it'd require adding ifdefs to
> >mkcpustr instead, which seems counterproductive.)
> 
> Didn't that change since v1?

No, even after removing the ifdefs around the build rules as you
suggested (and v3's fixes for the resulting build issues, notably
changing some -y's to -$(CONFIG_X86_FEATURE_NAMES)), the makefiles still
manage to not build mkcpustr or cpustr.h, because nothing depends on it.

I could change the build rules to generate an empty cpustr.h and avoid
this ifdef, but that'd require an additional ifdef block in the Makefile.

- Josh Triplett
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