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

    Signed-off-by: David Woodhouse <>
    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"
    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
    KBUILD_DEFCONFIG := $(ARCH)_defconfig
    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


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