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Re: Init not working in 64-bit kernel

To: Vadivelan@soc-soft.com
Subject: Re: Init not working in 64-bit kernel
From: Ralf Baechle <ralf@linux-mips.org>
Date: Fri, 17 Mar 2006 14:12:07 +0000
Cc: linux-mips@linux-mips.org
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On Fri, Mar 17, 2006 at 07:19:08PM +0530, Vadivelan@soc-soft.com wrote:

> I've another doubt. Is it enough to set only the bits KX,SX and UX of
> the status register to work in 64-bit mode?

KX, SX and UX will be set by the kernel itself on startup.

SX doesn't actually matter because Linux doesn't use the supervisor mode.

More for completness sake - there are some slight differences between the
various 64-bit processors if attempting to execute 64-bit instructions or
addresses on a processor configured to 32-bit mode.

> Though I've used the cross compiler mips64_fp_be-gcc from MontaVista,
> the generated vmlinux image seems to boot fine even without setting the
> above bits.
> I don't know if I'm operating in 32-bit or 64-bit mode.
> But I've enabled 64-bit support in kernel configuration.

Always 64-bit mode on a 64-bit kernels - even for 32-bit software.
Always 32-bit mode on 32-bit kernels - even on 64-bit hardware.

  Ralf

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