linux-kernel - Re: [PATCH 2/2] x86: Add "make tinyconfig" to configure the tiniest possible kernel

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Message-ID: <20140806224903.GA14782@jtriplet-mobl1>
Date:	Wed, 6 Aug 2014 15:49:03 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	"Luis R. Rodriguez" <mcgrof@...e.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86: Add "make tinyconfig" to configure the tiniest
 possible kernel

On Wed, Aug 06, 2014 at 03:38:56PM -0700, David Rientjes wrote:
> On Wed, 6 Aug 2014, Josh Triplett wrote:
> > diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> > index 1568678..2b5ca16 100644
> > --- a/arch/x86/Makefile
> > +++ b/arch/x86/Makefile
> > @@ -257,6 +257,10 @@ PHONY += kvmconfig
> >  kvmconfig:
> >  	$(call mergeconfig,kvm_guest)
> >  
> > +PHONY += tinyconfig
> > +tinyconfig: allnoconfig
> 
> Calling allnoconfig here makes "make tinyconfig" default to CONFIG_X86_32 
> even on 64 bit platforms and the caller would need to explicitly do
> "make ARCH=x86_64 tinyconfig" to avoid it.  It's not clear that this is 
> intended from the documentation of tinyconfig, that tiniest == 32 bit by 
> default.

Calling allnoconfig was quite intentional; this is intended to be the
smallest possible configuration, and unlike kvmconfig (which modifies an
existing configuration to make it suitable for a KVM guest), this
intentionally creates a specific new configuration from scratch.

32-bit produces a far smaller kernel than 64-bit, so having that as the
default for tinyconfig seems quite appropriate.  As you showed, it's
easy enough to override it if needed.  I'd expect many potential users
of tinyconfig for embedded systems to start with tinyconfig and then
immediately use menuconfig to enable a pile of additional options.

- Josh Triplett
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