[2.6 patch] i386 KEXEC must depend on X86_CMPXCHG64

[2.6 patch] i386 KEXEC must depend on X86_CMPXCHG64

[Adrian Bunk]

This patch fixes the following compile error with 
CONFIG_X86_CMPXCHG64=n:

<--  snip  -->

...
  CC      arch/i386/kernel/machine_kexec.o
arch/i386/kernel/machine_kexec.c: In function 'identity_map_page':
arch/i386/kernel/machine_kexec.c:78: error: implicit declaration of function 'set_64bit'
make[1]: *** [arch/i386/kernel/machine_kexec.o] Error 1

<--  snip  -->


Signed-off-by: Adrian Bunk <bunk@stusta.de>

--- linux-2.6.15-rc1-mm1-full/arch/i386/Kconfig.old	2005-11-18 00:44:29.000000000 +0100
+++ linux-2.6.15-rc1-mm1-full/arch/i386/Kconfig	2005-11-18 00:45:11.000000000 +0100
@@ -662,7 +662,7 @@
 
 config KEXEC
 	bool "kexec system call (EXPERIMENTAL)"
-	depends on EXPERIMENTAL
+	depends on EXPERIMENTAL && X86_CMPXCHG64
 	help
 	  kexec is a system call that implements the ability to shutdown your
 	  current kernel, and to start another kernel.  It is like a reboot

Re: [2.6 patch] i386 KEXEC must depend on X86_CMPXCHG64

[Eric W. Biederman]

Adrian Bunk <bunk@stusta.de> writes:

> This patch fixes the following compile error with 
> CONFIG_X86_CMPXCHG64=n:
>
> <--  snip  -->
>
> ...
>   CC      arch/i386/kernel/machine_kexec.o
> arch/i386/kernel/machine_kexec.c: In function 'identity_map_page':
> arch/i386/kernel/machine_kexec.c:78: error: implicit declaration of function
> 'set_64bit'
> make[1]: *** [arch/i386/kernel/machine_kexec.o] Error 1
>
> <--  snip  -->

Good catch but wrong fix.  This code works fine on a 386.  Or
it did last time I tried it.

This dependency only exists if 3 level page tables are configured.
CONFIG_X86_PAE

The call to set_64bit is a specialized version of set_pmd.
Which also uses set_64_bit.  So I don't see how your kernel can
even build without this.

The only way I can see this even being selected is building
a kernel for a 386 or 486 and wanting pae support.  Which won't
work on a 386 or a 486.  Making it a pointless exercise.

So I think either the pgtable-3level.h needs to fixed,
or we just make CONFIG_HIGHME64G depend on CONFIG_X86_CMPXCHG64.

Eric

[2.6 patch] i386: HIGHMEM64G must depend on X86_CMPXCHG64

[Adrian Bunk]

On Thu, Nov 17, 2005 at 06:47:27PM -0700, Eric W. Biederman wrote:
>...
> So I think either the pgtable-3level.h needs to fixed,
> or we just make CONFIG_HIGHME64G depend on CONFIG_X86_CMPXCHG64.

Sounds reasonable (and sorry for the late answer).

Patch below.

> Eric

cu
Adrian


<--  snip  -->


Due to the usage of set_64bit in include/asm-i386/pgtable-3level.h, 
HIGHMEM64G must depend on X86_CMPXCHG64.


--- linux-2.6.16-rc1-mm3-386/arch/i386/Kconfig.old	2006-01-28 16:04:45.000000000 +0100
+++ linux-2.6.16-rc1-mm3-386/arch/i386/Kconfig	2006-01-28 16:05:25.000000000 +0100
@@ -442,6 +442,7 @@
 
 config HIGHMEM64G
 	bool "64GB"
+	depends on X86_CMPXCHG64
 	help
 	  Select this if you have a 32-bit processor and more than 4
 	  gigabytes of physical RAM.