Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
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arch/x86/Kconfig
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arch/x86/Kconfig
···
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uniprocessor machines. On a uniprocessor machine, the kernel
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will run faster if you say N here.
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Note that if you say Y here and choose architecture "586" or
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"Pentium" under "Processor family", the kernel will not work on 486
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architectures. Similarly, multiprocessor kernels for the "PPro"
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architecture may not work on all Pentium based boards.
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People using multiprocessor machines who say Y here should also say
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Y to "Enhanced Real Time Clock Support", below. The "Advanced Power
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Management" code will be disabled if you say Y here.
···
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This driver does not spin down disk drives (see the hdparm(8)
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manpage ("man 8 hdparm") for that), and it doesn't turn off
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VESA-compliant "green" monitors.
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This driver does not support the TI 4000M TravelMate and the ACER
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486/DX4/75 because they don't have compliant BIOSes. Many "green"
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desktop machines also don't have compliant BIOSes, and this driver
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may cause those machines to panic during the boot phase.
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Generally, if you don't have a battery in your machine, there isn't
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much point in using this driver and you should say N. If you get
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arch/x86/Kconfig.cpu
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arch/x86/Kconfig.cpu
···
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This is the processor type of your CPU. This information is
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used for optimizing purposes. In order to compile a kernel
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that can run on all supported x86 CPU types (albeit not
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optimally fast), you can specify "486" here.
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optimally fast), you can specify "586" here.
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Note that the 386 is no longer supported, this includes
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Note that the 386 and 486 is no longer supported, this includes
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AMD/Cyrix/Intel 386DX/DXL/SL/SLC/SX, Cyrix/TI 486DLC/DLC2,
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UMC 486SX-S and the NexGen Nx586.
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UMC 486SX-S and the NexGen Nx586, AMD ELAN and all 486 based
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CPUs.
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The kernel will not necessarily run on earlier architectures than
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the one you have chosen, e.g. a Pentium optimized kernel will run on
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a PPro, but not necessarily on a i486.
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Here are the settings recommended for greatest speed:
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- "486" for the AMD/Cyrix/IBM/Intel 486DX/DX2/DX4 or
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SL/SLC/SLC2/SLC3/SX/SX2 and UMC U5D or U5S.
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- "586" for generic Pentium CPUs lacking the TSC
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(time stamp counter) register.
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- "Pentium-Classic" for the Intel Pentium.
···
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See each option's help text for additional details. If you don't know
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what to do, choose "Pentium-Pro".
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config M486SX
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bool "486SX"
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depends on X86_32
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help
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Select this for an 486-class CPU without an FPU such as
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AMD/Cyrix/IBM/Intel SL/SLC/SLC2/SLC3/SX/SX2 and UMC U5S.
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config M486
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bool "486DX"
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depends on X86_32
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help
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Select this for an 486-class CPU such as AMD/Cyrix/IBM/Intel
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486DX/DX2/DX4 and UMC U5D.
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config M586
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bool "586/K5/5x86/6x86/6x86MX"
···
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stores for this CPU, which can increase performance of some
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operations.
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config MELAN
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bool "AMD Elan"
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depends on X86_32
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help
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Select this for an AMD Elan processor.
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-
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Do not use this option for K6/Athlon/Opteron processors!
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config MGEODEGX1
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bool "GeodeGX1"
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depends on X86_32
···
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int
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default "7" if MPENTIUM4
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default "6" if MK7 || MPENTIUMM || MATOM || MVIAC7 || X86_GENERIC || X86_64
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default "4" if MELAN || M486SX || M486 || MGEODEGX1
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default "4" if MGEODEGX1
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default "5" if MWINCHIP3D || MWINCHIPC6 || MCRUSOE || MEFFICEON || MCYRIXIII || MK6 || MPENTIUMIII || MPENTIUMII || M686 || M586MMX || M586TSC || M586 || MVIAC3_2 || MGEODE_LX
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config X86_F00F_BUG
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def_bool y
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depends on M586MMX || M586TSC || M586 || M486SX || M486
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depends on M586MMX || M586TSC || M586
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config X86_INVD_BUG
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def_bool y
···
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config X86_ALIGNMENT_16
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def_bool y
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depends on MWINCHIP3D || MWINCHIPC6 || MCYRIXIII || MELAN || MK6 || M586MMX || M586TSC || M586 || M486SX || M486 || MVIAC3_2 || MGEODEGX1
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depends on MWINCHIP3D || MWINCHIPC6 || MCYRIXIII || MK6 || M586MMX || M586TSC || M586 || MVIAC3_2 || MGEODEGX1
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config X86_INTEL_USERCOPY
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def_bool y
···
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int
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default "64" if X86_64
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default "6" if X86_32 && (MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MVIAC3_2 || MVIAC7 || MEFFICEON || MATOM || MK7)
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default "5" if X86_32 && X86_CX8
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default "4"
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default "5"
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config X86_DEBUGCTLMSR
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def_bool y
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depends on !(MK6 || MWINCHIPC6 || MWINCHIP3D || MCYRIXIII || M586MMX || M586TSC || M586 || M486SX || M486) && !UML
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depends on !(MK6 || MWINCHIPC6 || MWINCHIP3D || MCYRIXIII || M586MMX || M586TSC || M586) && !UML
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config IA32_FEAT_CTL
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def_bool y
···
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config CPU_SUP_CYRIX_32
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default y
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bool "Support Cyrix processors" if PROCESSOR_SELECT
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depends on M486SX || M486 || M586 || M586TSC || M586MMX || (EXPERT && !64BIT)
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depends on M586 || M586TSC || M586MMX || (EXPERT && !64BIT)
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help
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This enables detection, tunings and quirks for Cyrix processors
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-2
arch/x86/Makefile_32.cpu
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arch/x86/Makefile_32.cpu
···
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align := -falign-functions=0 -falign-jumps=0 -falign-loops=0
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endif
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cflags-$(CONFIG_M486SX) += -march=i486
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cflags-$(CONFIG_M486) += -march=i486
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cflags-$(CONFIG_M586) += -march=i586
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cflags-$(CONFIG_M586TSC) += -march=i586
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cflags-$(CONFIG_M586MMX) += -march=pentium-mmx
-6
arch/x86/include/asm/vermagic.h
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arch/x86/include/asm/vermagic.h
···
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#ifdef CONFIG_X86_64
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/* X86_64 does not define MODULE_PROC_FAMILY */
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#elif defined CONFIG_M486SX
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#define MODULE_PROC_FAMILY "486SX "
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#elif defined CONFIG_M486
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#define MODULE_PROC_FAMILY "486 "
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#elif defined CONFIG_M586
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#define MODULE_PROC_FAMILY "586 "
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#elif defined CONFIG_M586TSC
···
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#define MODULE_PROC_FAMILY "K6 "
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#elif defined CONFIG_MK7
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#define MODULE_PROC_FAMILY "K7 "
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#elif defined CONFIG_MELAN
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#define MODULE_PROC_FAMILY "ELAN "
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#elif defined CONFIG_MCRUSOE
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#define MODULE_PROC_FAMILY "CRUSOE "
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#elif defined CONFIG_MEFFICEON