Commit 8b793a92 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86/cpu: Remove M486/M486SX/ELAN support 



In the x86 architecture we have various complicated hardware emulation
facilities on x86-32 to support ancient 32-bit CPUs that very very few
people are using with modern kernels. This compatibility glue is sometimes
even causing problems that people spend time to resolve, which time could
be spent on other things.

As Linus recently remarked:

 > I really get the feeling that it's time to leave i486 support behind.
 > There's zero real reason for anybody to waste one second of
 > development effort on this kind of issue.

Implement the first step and remove M486/M486SX/ELAN support:

  CONFIG_M486SX
  CONFIG_M486
  CONFIG_MELAN

[ There's no recent M486=y kernel package for any mainstream x86
  32-bit distribution available that I've been able to find, so
  actual users should not be impacted, and any legacy users can
  keep using older kernels. ]

Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarArnd Bergmann <arnd@arndb.de>
Acked-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Cc: Ahmed S. Darwish <darwi@linutronix.de>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: John Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20251214084710.3606385-2-mingo@kernel.org
parent 7aaa8047

arch/x86/Kconfig

+0 −10
Original line number Diff line number Diff line
@@ -446,11 +446,6 @@ config SMP 
	  uniprocessor machines. On a uniprocessor machine, the kernel

	  will run faster if you say N here.



	  Note that if you say Y here and choose architecture "586" or

	  "Pentium" under "Processor family", the kernel will not work on 486

	  architectures. Similarly, multiprocessor kernels for the "PPro"

	  architecture may not work on all Pentium based boards.



	  People using multiprocessor machines who say Y here should also say

	  Y to "Enhanced Real Time Clock Support", below. The "Advanced Power

	  Management" code will be disabled if you say Y here.
@@ -2771,11 +2766,6 @@ menuconfig APM 
	  manpage ("man 8 hdparm") for that), and it doesn't turn off

	  VESA-compliant "green" monitors.



	  This driver does not support the TI 4000M TravelMate and the ACER

	  486/DX4/75 because they don't have compliant BIOSes. Many "green"

	  desktop machines also don't have compliant BIOSes, and this driver

	  may cause those machines to panic during the boot phase.



	  Generally, if you don't have a battery in your machine, there isn't

	  much point in using this driver and you should say N. If you get

	  random kernel OOPSes or reboots that don't seem to be related to

arch/x86/Kconfig.cpu

+10 −34
Original line number Diff line number Diff line
@@ -8,19 +8,18 @@ choice 
	  This is the processor type of your CPU. This information is

	  used for optimizing purposes. In order to compile a kernel

	  that can run on all supported x86 CPU types (albeit not

	  optimally fast), you can specify "486" here.

	  optimally fast), you can specify "586" here.



	  Note that the 386 is no longer supported, this includes

	  Note that the 386 and 486 is no longer supported, this includes

	  AMD/Cyrix/Intel 386DX/DXL/SL/SLC/SX, Cyrix/TI 486DLC/DLC2,

	  UMC 486SX-S and the NexGen Nx586.

	  UMC 486SX-S and the NexGen Nx586, AMD ELAN and all 486 based

	  CPUs.



	  The kernel will not necessarily run on earlier architectures than

	  the one you have chosen, e.g. a Pentium optimized kernel will run on

	  a PPro, but not necessarily on a i486.



	  Here are the settings recommended for greatest speed:

	  - "486" for the AMD/Cyrix/IBM/Intel 486DX/DX2/DX4 or

	    SL/SLC/SLC2/SLC3/SX/SX2 and UMC U5D or U5S.

	  - "586" for generic Pentium CPUs lacking the TSC

	    (time stamp counter) register.

	  - "Pentium-Classic" for the Intel Pentium.
@@ -46,20 +45,6 @@ choice 
	  See each option's help text for additional details. If you don't know

	  what to do, choose "Pentium-Pro".



config M486SX

	bool "486SX"

	depends on X86_32

	help

	  Select this for an 486-class CPU without an FPU such as

	  AMD/Cyrix/IBM/Intel SL/SLC/SLC2/SLC3/SX/SX2 and UMC U5S.



config M486

	bool "486DX"

	depends on X86_32

	help

	  Select this for an 486-class CPU such as AMD/Cyrix/IBM/Intel

	  486DX/DX2/DX4 and UMC U5D.



config M586

	bool "586/K5/5x86/6x86/6x86MX"

	depends on X86_32
@@ -188,14 +173,6 @@ config MWINCHIP3D 
	  stores for this CPU, which can increase performance of some

	  operations.



config MELAN

	bool "AMD Elan"

	depends on X86_32

	help

	  Select this for an AMD Elan processor.



	  Do not use this option for K6/Athlon/Opteron processors!



config MGEODEGX1

	bool "GeodeGX1"

	depends on X86_32
@@ -292,12 +269,12 @@ config X86_L1_CACHE_SHIFT 
	int

	default "7" if MPENTIUM4

	default "6" if MK7 || MPENTIUMM || MATOM || MVIAC7 || X86_GENERIC || X86_64

	default "4" if MELAN || M486SX || M486 || MGEODEGX1

	default "4" if MGEODEGX1

	default "5" if MWINCHIP3D || MWINCHIPC6 || MCRUSOE || MEFFICEON || MCYRIXIII || MK6 || MPENTIUMIII || MPENTIUMII || M686 || M586MMX || M586TSC || M586 || MVIAC3_2 || MGEODE_LX



config X86_F00F_BUG

	def_bool y

	depends on M586MMX || M586TSC || M586 || M486SX || M486

	depends on M586MMX || M586TSC || M586



config X86_INVD_BUG

	def_bool y
@@ -305,7 +282,7 @@ config X86_INVD_BUG 


config X86_ALIGNMENT_16

	def_bool y

	depends on MWINCHIP3D || MWINCHIPC6 || MCYRIXIII || MELAN || MK6 || M586MMX || M586TSC || M586 || M486SX || M486 || MVIAC3_2 || MGEODEGX1

	depends on MWINCHIP3D || MWINCHIPC6 || MCYRIXIII || MK6 || M586MMX || M586TSC || M586 || MVIAC3_2 || MGEODEGX1



config X86_INTEL_USERCOPY

	def_bool y
@@ -337,12 +314,11 @@ config X86_MINIMUM_CPU_FAMILY 
	int

	default "64" if X86_64

	default "6" if X86_32 && (MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MVIAC3_2 || MVIAC7 || MEFFICEON || MATOM || MK7)

	default "5" if X86_32 && X86_CX8

	default "4"

	default "5"



config X86_DEBUGCTLMSR

	def_bool y

	depends on !(MK6 || MWINCHIPC6 || MWINCHIP3D || MCYRIXIII || M586MMX || M586TSC || M586 || M486SX || M486) && !UML

	depends on !(MK6 || MWINCHIPC6 || MWINCHIP3D || MCYRIXIII || M586MMX || M586TSC || M586) && !UML



config IA32_FEAT_CTL

	def_bool y
@@ -378,7 +354,7 @@ config CPU_SUP_INTEL 
config CPU_SUP_CYRIX_32

	default y

	bool "Support Cyrix processors" if PROCESSOR_SELECT

	depends on M486SX || M486 || M586 || M586TSC || M586MMX || (EXPERT && !64BIT)

	depends on M586 || M586TSC || M586MMX || (EXPERT && !64BIT)

	help

	  This enables detection, tunings and quirks for Cyrix processors

arch/x86/Makefile_32.cpu

+0 −2
Original line number Diff line number Diff line
@@ -10,8 +10,6 @@ else 
align		:= -falign-functions=0 -falign-jumps=0 -falign-loops=0

endif



cflags-$(CONFIG_M486SX)		+= -march=i486

cflags-$(CONFIG_M486)		+= -march=i486

cflags-$(CONFIG_M586)		+= -march=i586

cflags-$(CONFIG_M586TSC)	+= -march=i586

cflags-$(CONFIG_M586MMX)	+= -march=pentium-mmx

arch/x86/include/asm/vermagic.h

+0 −6
Original line number Diff line number Diff line
@@ -5,10 +5,6 @@ 


#ifdef CONFIG_X86_64

/* X86_64 does not define MODULE_PROC_FAMILY */

#elif defined CONFIG_M486SX

#define MODULE_PROC_FAMILY "486SX "

#elif defined CONFIG_M486

#define MODULE_PROC_FAMILY "486 "

#elif defined CONFIG_M586

#define MODULE_PROC_FAMILY "586 "

#elif defined CONFIG_M586TSC
@@ -31,8 +27,6 @@ 
#define MODULE_PROC_FAMILY "K6 "

#elif defined CONFIG_MK7

#define MODULE_PROC_FAMILY "K7 "

#elif defined CONFIG_MELAN

#define MODULE_PROC_FAMILY "ELAN "

#elif defined CONFIG_MCRUSOE

#define MODULE_PROC_FAMILY "CRUSOE "

#elif defined CONFIG_MEFFICEON