linux-kernel - Re: config automatically switches from 32-bit to 64-bit for x86

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Date:	Fri, 4 Jun 2010 11:53:17 +0530
From:	Jaswinder Singh Rajput <jaswinderlinux@...il.com>
To:	Michal Marek <mmarek@...e.cz>
Cc:	Sam Ravnborg <sam@...nborg.org>,
	Christoph Hellwig <hch@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: config automatically switches from 32-bit to 64-bit for x86

Hello Michal and Sam,

On Thu, Jun 3, 2010 at 7:00 PM, Michal Marek <mmarek@...e.cz> wrote:
> On Thu, May 27, 2010 at 08:46:53PM +0200, Sam Ravnborg wrote:
>> On Thu, May 27, 2010 at 11:49:16AM -0400, Christoph Hellwig wrote:
>> > On Thu, May 27, 2010 at 05:37:36AM +0530, Jaswinder Singh Rajput wrote:
>> > > Hello,
>> > >
>> > > I am trying to build 32 bit kernel image on 64-bit machine but after
>> > > 'make menuconfig' it automatically switches 32-bit to 64-bit.
>> > >
>> > > Is this a BUG or did intentionally.
>> >
>> > I think it's intentional, but I'm really annoyed by this behaviour.
>>
>> The request when we did the merge of 32 and 64 bit was that we
>> should continue to build 64bit kernels on 64 bit machines.
>> And likewise for 32bit.
>> Because this was what the users where used to.
>>
>> We could simplify metters by defining new rules.
>> As you suggest that uname on an intel box always resulted in ARCH=x86.
>> But then people would complain why a 32 bit kernel is default when
>> the box is 64 bit.
>
> Which is not acceptable, IMO. An x86_64 distro typically has a complete
> 64bit userspace including /sbin/init, so the default kernel has to be
> 64bit.
>
> What about always making the prompt visible, so that the previously set
> value gets reused? The downside is that 'make ARCH=i386 menuconfig' in a
> clean tree on x86_64 will default to 64bit, because it will find the
> setting in the config of the running 64bit kernel :(. But after manually
> turning CONFIG_64BIT off, the setting will be preserved.
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index dcb0593..05ec418 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -3,7 +3,7 @@ mainmenu "Linux Kernel Configuration for x86"
>
>  # Select 32 or 64 bit
>  config 64BIT
> -       bool "64-bit kernel" if ARCH = "x86"
> +       bool "64-bit kernel"
>        default ARCH = "x86_64"
>        ---help---
>          Say yes to build a 64-bit kernel - formerly known as x86_64
>

This patch works !!

Thanks,
--
Jaswinder Singh.
--
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