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: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Dave 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

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e2df1b147184a6ed451a9d82a6cbfc72a78aa253..6627b6d79d30f3b923b352fc7cc8d61db2361359 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -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

diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index f928cf6e32524e32f10f9d4f35f82ab5c4fb0421..d7ba9219cb47dceba8fa46f34e176805c46d2cf3 100644 (file)
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -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
 

diff --git a/arch/x86/Makefile_32.cpu b/arch/x86/Makefile_32.cpu
index a3dda95e47f412047f9d39d0fdab5f52c667010c..7c9898c1537613f8e98de31df90bcad359dde5d7 100644 (file)
--- a/arch/x86/Makefile_32.cpu
+++ b/arch/x86/Makefile_32.cpu
@@ -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

diff --git a/arch/x86/include/asm/vermagic.h b/arch/x86/include/asm/vermagic.h
index 5d471253c75549c85d1d697638af853397430304..eda233a90ea86a7333d0e40568fd4458dd9f9565 100644 (file)
--- a/arch/x86/include/asm/vermagic.h
+++ b/arch/x86/include/asm/vermagic.h
@@ -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