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    SubjectRe: [PATCH v3] x86, kconfig: Default to ARCH=x86 to avoid overriding CONFIG_64BIT
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    Hi,

    On Fri, Jul 29, 2011 at 8:49 PM, David Woodhouse <dwmw2@infradead.org> wrote:
    > I *frequently* waste a bunch of time when I take a 32-bit .config from a
    > test machine and try to build it on a faster 64-bit system, and its
    > existing setting of CONFIG_64BIT=n gets *changed* to match the build host.
    >
    > This is because the default setting for $ARCH when discovered from
    > 'uname' is one of the legacy pre-x86-merge values (i386 or x86_64),
    > which effectively force the setting of CONFIG_64BIT to match. We should
    > default to ARCH=x86 instead, finally completing the merge that we
    > started so long ago.
    >
    > This patch preserves the behaviour of the legacy ARCH settings for commands
    > such as:
    >
    >   make ARCH=x86_64 randconfig
    >   make ARCH=i386 randconfig
    >
    > ... although since my commit "Enable 'make CONFIG_FOO=y oldconfig'" those
    > would be better expressed as:
    >
    >   make CONFIG_64BIT=y randconfig
    >   make CONFIG_64BIT=n randconfig
    >
    > ... since that is a more generic way to set *any* config option, and
    > there's no other technical reason to keep the legacy ARCH values around
    > any more just to achieve that purpose; they could be removed at any
    > time.
    >
    > Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
    > Link: http://lkml.kernel.org/r/1306707270.2029.377.camel@i7.infradead.org
    > ---
    > v2: Explicitly turn off CONFIG_64BIT in i386_defconfig. The default for
    >    CONFIG_64BIT has *changed* (from n to y) for ARCH=x86, so it needs to
    >    be explicitly turned off or 'make i386_defconfig' will give you 64-bit.
    > v3: Same patch as before; just updated changelog.
    >
    >  Makefile                        |    3 ++-
    >  arch/x86/Kconfig                |    2 +-
    >  arch/x86/Makefile               |    4 ++++
    >  arch/x86/configs/i386_defconfig |    1 +
    >  4 files changed, 8 insertions(+), 2 deletions(-)
    >
    > diff --git a/Makefile b/Makefile
    > index d018956..303df9b 100644
    > --- a/Makefile
    > +++ b/Makefile
    > @@ -165,7 +165,8 @@ export srctree objtree VPATH
    >  # then ARCH is assigned, getting whatever value it gets normally, and
    >  # SUBARCH is subsequently ignored.
    >
    > -SUBARCH := $(shell uname -m | sed -e s/i.86/i386/ -e s/sun4u/sparc64/ \
    > +SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
    > +                                 -e s/sun4u/sparc64/ \
    >                                  -e s/arm.*/arm/ -e s/sa110/arm/ \
    >                                  -e s/s390x/s390/ -e s/parisc64/parisc/ \
    >                                  -e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
    > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    > index 153aa6f..9467fdd 100644
    > --- a/arch/x86/Kconfig
    > +++ b/arch/x86/Kconfig
    > @@ -1,7 +1,7 @@
    >  # Select 32 or 64 bit
    >  config 64BIT
    >        bool "64-bit kernel" if ARCH = "x86"
    > -       default ARCH = "x86_64"
    > +       default ARCH != "i386"
    If I'm reading this correctly, does this mean that someone doing an
    'allyesconfig' on an i386 machine will get a configuration for a
    64bits kernel[0] ? With your logic, you would require the user to
    manually specify CONFIG_64BIT=n, which should be automatic on such a
    system...

    This logic seems broken to me.

    - Arnaud

    [0]: both ARCH and SUBARCH will be x86, so the conditional will translate to 'y'

    >        ---help---
    >          Say yes to build a 64-bit kernel - formerly known as x86_64
    >          Say no to build a 32-bit kernel - formerly known as i386
    > diff --git a/arch/x86/Makefile b/arch/x86/Makefile
    > index b02e509..94c2d8c 100644
    > --- a/arch/x86/Makefile
    > +++ b/arch/x86/Makefile
    > @@ -2,7 +2,11 @@
    >
    >  # select defconfig based on actual architecture
    >  ifeq ($(ARCH),x86)
    > +  ifeq ($(shell uname -m),x86_64)
    > +        KBUILD_DEFCONFIG := x86_64_defconfig
    > +  else
    >         KBUILD_DEFCONFIG := i386_defconfig
    > +  endif
    >  else
    >         KBUILD_DEFCONFIG := $(ARCH)_defconfig
    >  endif
    > diff --git a/arch/x86/configs/i386_defconfig b/arch/x86/configs/i386_defconfig
    > index 2bf18059f..5f96c1c 100644
    > --- a/arch/x86/configs/i386_defconfig
    > +++ b/arch/x86/configs/i386_defconfig
    > @@ -1,3 +1,4 @@
    > +# CONFIG_64BIT is not set
    >  CONFIG_EXPERIMENTAL=y
    >  # CONFIG_LOCALVERSION_AUTO is not set
    >  CONFIG_SYSVIPC=y
    > --
    > 1.7.6
    >
    >
    >
    > --
    > dwmw2
    >
    >
    --
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