[PATCH 1/1] [x86] Configuration options to compile out x86 CPU support code

[PATCH 1/1] [x86] Configuration options to compile out x86 CPU support code

[Thomas Petazzoni]

This patch adds some configuration options that allow to compile out
CPU vendor-specific code in x86 kernels (in arch/x86/kernel/cpu). The
new configuration options are only visible when CONFIG_EMBEDDED is
selected, as they are mostly interesting for space savings reasons.

An example of size saving, on x86 with only Intel CPU support:

   text	   data	    bss	    dec	    hex	filename
1125479	 118760	 212992	1457231	 163c4f	vmlinux.old
1121355	 116536	 212992	1450883	 162383	vmlinux
  -4124   -2224       0   -6348   -18CC +/-

However, I'm not exactly sure that the Kconfig wording is correct with
regard to !64BIT / 64BIT.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: tglx@linutronix.de
Cc: mingo@redhat.com
Cc: hpa@zytor.com
Cc: michael@free-electrons.com
---
 arch/x86/Kconfig.cpu         |   70 ++++++++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/cpu/Makefile |   19 ++++++-----
 include/asm-x86/bugs.h       |    5 +++
 3 files changed, 85 insertions(+), 9 deletions(-)

diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 2c518fb..6156ac2 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -415,3 +415,73 @@ config X86_MINIMUM_CPU_FAMILY
 config X86_DEBUGCTLMSR
 	def_bool y
 	depends on !(MK6 || MWINCHIPC6 || MWINCHIP2 || MWINCHIP3D || MCYRIXIII || M586MMX || M586TSC || M586 || M486 || M386)
+
+menuconfig PROCESSOR_SELECT
+	default y
+	bool "Supported processor vendors" if EMBEDDED
+	help
+	  This lets you choose what x86 vendor support code your kernel
+	  will include.
+
+config CPU_SUP_INTEL_32
+	default y
+	bool "Support Intel processors" if PROCESSOR_SELECT
+	depends on !64BIT
+	help
+	  This enables extended support for Intel processors
+
+config CPU_SUP_INTEL_64
+	default y
+	bool "Support Intel processors" if PROCESSOR_SELECT
+	depends on 64BIT
+	help
+	  This enables extended support for Intel processors
+
+config CPU_SUP_CYRIX_32
+	default y
+	bool "Support Cyrix processors" if PROCESSOR_SELECT
+	depends on !64BIT
+	help
+	  This enables extended support for Cyrix processors
+
+config CPU_SUP_AMD_32
+	default y
+	bool "Support AMD processors" if PROCESSOR_SELECT
+	depends on !64BIT
+	help
+	  This enables extended support for AMD processors
+
+config CPU_SUP_AMD_64
+	default y
+	bool "Support AMD processors" if PROCESSOR_SELECT
+	depends on 64BIT
+	help
+	  This enables extended support for AMD processors
+
+config CPU_SUP_CENTAUR_32
+	default y
+	bool "Support Centaur processors" if PROCESSOR_SELECT
+	depends on !64BIT
+	help
+	  This enables extended support for Centaur processors
+
+config CPU_SUP_CENTAUR_64
+	default y
+	bool "Support Centaur processors" if PROCESSOR_SELECT
+	depends on 64BIT
+	help
+	  This enables extended support for Centaur processors
+
+config CPU_SUP_TRANSMETA_32
+	default y
+	bool "Support Transmeta processors" if PROCESSOR_SELECT
+	depends on !64BIT
+	help
+	  This enables extended support for Transmeta processors
+
+config CPU_SUP_UMC_32
+	default y
+	bool "Support UMC processors" if PROCESSOR_SELECT
+	depends on !64BIT
+	help
+	  This enables extended support for UMC processors
diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
index ee76eaa..a35ee92 100644
--- a/arch/x86/kernel/cpu/Makefile
+++ b/arch/x86/kernel/cpu/Makefile
@@ -7,15 +7,16 @@ obj-y			+= proc.o feature_names.o
 
 obj-$(CONFIG_X86_32)	+= common.o bugs.o
 obj-$(CONFIG_X86_64)	+= common_64.o bugs_64.o
-obj-$(CONFIG_X86_32)	+= amd.o
-obj-$(CONFIG_X86_64)	+= amd_64.o
-obj-$(CONFIG_X86_32)	+= cyrix.o
-obj-$(CONFIG_X86_32)	+= centaur.o
-obj-$(CONFIG_X86_64)	+= centaur_64.o
-obj-$(CONFIG_X86_32)	+= transmeta.o
-obj-$(CONFIG_X86_32)	+= intel.o
-obj-$(CONFIG_X86_64)	+= intel_64.o
-obj-$(CONFIG_X86_32)	+= umc.o
+
+obj-$(CONFIG_CPU_SUP_AMD_32)		+= amd.o
+obj-$(CONFIG_CPU_SUP_AMD_64)		+= amd_64.o
+obj-$(CONFIG_CPU_SUP_CYRIX_32)		+= cyrix.o
+obj-$(CONFIG_CPU_SUP_CENTAUR_32)	+= centaur.o
+obj-$(CONFIG_CPU_SUP_CENTAUR_64)	+= centaur_64.o
+obj-$(CONFIG_CPU_SUP_TRANSMETA_32)	+= transmeta.o
+obj-$(CONFIG_CPU_SUP_INTEL_32)		+= intel.o
+obj-$(CONFIG_CPU_SUP_INTEL_64)		+= intel_64.o
+obj-$(CONFIG_CPU_SUP_UMC_32)		+= umc.o
 
 obj-$(CONFIG_X86_MCE)	+= mcheck/
 obj-$(CONFIG_MTRR)	+= mtrr/
diff --git a/include/asm-x86/bugs.h b/include/asm-x86/bugs.h
index 021cbdd..66cf8c9 100644
--- a/include/asm-x86/bugs.h
+++ b/include/asm-x86/bugs.h
@@ -2,6 +2,11 @@
 #define _ASM_X86_BUGS_H
 
 extern void check_bugs(void);
+
+#ifdef CONFIG_CPU_SUP_INTEL_32
 int ppro_with_ram_bug(void);
+#else
+#define ppro_with_ram_bug() (0)
+#endif
 
 #endif /* _ASM_X86_BUGS_H */
-- 
1.5.4.3

Re: [PATCH 1/1] [x86] Configuration options to compile out x86 CPU support code

[Bodo Eggert]

Thomas Petazzoni <thomas.petazzoni@free-electrons.com> wrote:

> This patch adds some configuration options that allow to compile out
> CPU vendor-specific code in x86 kernels (in arch/x86/kernel/cpu). The
> new configuration options are only visible when CONFIG_EMBEDDED is
> selected, as they are mostly interesting for space savings reasons.

> +menuconfig PROCESSOR_SELECT
> +     default y
> +     bool "Supported processor vendors" if EMBEDDED
> +     help
> +       This lets you choose what x86 vendor support code your kernel
> +       will include.
> +
> +config CPU_SUP_INTEL_32
> +     default y
> +     bool "Support Intel processors" if PROCESSOR_SELECT
> +     depends on !64BIT
> +     help
> +       This enables extended support for Intel processors
> +

I don't think having a generic kernel for only Intel CPUs makes much sense,
and OTOH, if you optimize for e.g. Athlon CPUs, you're likely to not need
Intel code on that machine - even on desktop systems.

What about an option to "Include code for CPUs from all supported vendors",
invisible and y for generic kernels?

Re: [PATCH 1/1] [x86] Configuration options to compile out x86 CPU support code

[Ingo Molnar]

* Thomas Petazzoni <thomas.petazzoni@free-electrons.com> wrote:

> This patch adds some configuration options that allow to compile out 
> CPU vendor-specific code in x86 kernels (in arch/x86/kernel/cpu). The 
> new configuration options are only visible when CONFIG_EMBEDDED is 
> selected, as they are mostly interesting for space savings reasons.
> 
> An example of size saving, on x86 with only Intel CPU support:
> 
>    text	   data	    bss	    dec	    hex	filename
> 1125479	 118760	 212992	1457231	 163c4f	vmlinux.old
> 1121355	 116536	 212992	1450883	 162383	vmlinux
>   -4124   -2224       0   -6348   -18CC +/-
> 
> However, I'm not exactly sure that the Kconfig wording is correct with 
> regard to !64BIT / 64BIT.

applied to tip/x86/cpu, thanks Thomas. (I've done a trivial cleanup: 
converted the macro to an inline.)

Peter, do you like this version of the patch or would you like further 
improvements?

	Ingo

Re: [PATCH 1/1] [x86] Configuration options to compile out x86 CPU support code

[Ingo Molnar]

-tip testing found a couple of build failures:

  LD      .tmp_vmlinux1
arch/x86/lib/lib.a(usercopy_32.o): In function `__copy_to_user_ll':
(.text+0x11e): undefined reference to `movsl_mask'
arch/x86/lib/lib.a(usercopy_32.o): In function `__copy_from_user_ll':
(.text+0x1fa): undefined reference to `movsl_mask'
arch/x86/lib/lib.a(usercopy_32.o): In function 
`__copy_from_user_ll_nozero':
(.text+0x2d6): undefined reference to `movsl_mask'
arch/x86/lib/lib.a(usercopy_32.o): In function `copy_from_user':
(.text+0x5ac): undefined reference to `movsl_mask'
arch/x86/lib/lib.a(usercopy_32.o): In function `copy_to_user':
(.text+0x6bf): undefined reference to `movsl_mask'
make: *** [.tmp_vmlinux1] Error 1

with:

  http://redhat.com/~mingo/misc/config-Fri_Aug_15_16_35_03_CEST_2008.bad

and:

arch/x86/kvm/built-in.o: In function `paging64_cmpxchg_gpte':
mmu.c:(.text+0xa80d): undefined reference to `cmpxchg_486_u64'

with:

  http://redhat.com/~mingo/misc/config-Fri_Aug_15_16_27_47_CEST_2008.bad

reverting your change solved both of them.

i still have the commit in tip/x86/cpu so please send a delta fix ontop 
of your previous patch once you figure out the problem. Thanks,

	Ingo

Re: [PATCH 1/1] [x86] Configuration options to compile out x86 CPU support code

[H. Peter Anvin]

Ingo Molnar wrote:
> * Thomas Petazzoni <thomas.petazzoni@free-electrons.com> wrote:
> 
>> This patch adds some configuration options that allow to compile out 
>> CPU vendor-specific code in x86 kernels (in arch/x86/kernel/cpu). The 
>> new configuration options are only visible when CONFIG_EMBEDDED is 
>> selected, as they are mostly interesting for space savings reasons.
>>
>> An example of size saving, on x86 with only Intel CPU support:
>>
>>    text	   data	    bss	    dec	    hex	filename
>> 1125479	 118760	 212992	1457231	 163c4f	vmlinux.old
>> 1121355	 116536	 212992	1450883	 162383	vmlinux
>>   -4124   -2224       0   -6348   -18CC +/-
>>
>> However, I'm not exactly sure that the Kconfig wording is correct with 
>> regard to !64BIT / 64BIT.
> 
> applied to tip/x86/cpu, thanks Thomas. (I've done a trivial cleanup: 
> converted the macro to an inline.)
> 
> Peter, do you like this version of the patch or would you like further 
> improvements?
> 

I'm fine with it.

I think there might still be cross-dependencies, but it doesn't break 
anything old, so we can deal with that via bug reports.

The other thing that probably should be done is breaking out the 
Intel-specific versus generic parts of intel_cacheinfo.c.

	-hpa