Re: [PATCH v3 00/10] x86: 32-bit cleanups

Ingo Molnar
2025-02-27T10:34:51Z

* Arnd Bergmann <arnd@kernel.org> wrote:

> From: Arnd Bergmann <arnd@arndb.de>
>
> While looking at 32-bit arm cleanups, I came across some related topics
> on x86 and ended up making a series for those as well.
>
> Primarily this is about running 32-bit kernels on 64-bit hardware,
> which usually works but should probably be discouraged more clearly by
> only providing support for features that are used on real 32-bit hardware:
>
> I found only a few 2003-era high-end servers (HP DL740 and DL760 G2)
> that were the only possible remaining uses of HIGHMEM64G and BIGSMP after
> the removal of 32-bit NUMA machines in 2014. Similarly, there is only
> one generation of hardware with support for VT-x. All these features
> can be removed without hurting users.
>
> In the CPU selection, building a 32-bit kernel optimized for AMD K8
> or Intel Core2 is anachronistic, so instead only 32-bit CPU types need
> to be offered as optimization targets. The "generic" target on 64-bit
> turned out to be slightly broken, so I included a fix for that as well.
>
> Changes since v2:
>
> - Add a patch for EISA
> - keep PHYS_ADDR_T_64BIT enabled for PAE kernels
> - drop the Kconfig.platforms and CONFIG_X86_64_NATIVE patches for now
> - improve changelog texts
>
> Changes since v1:
>
> - Don't include patch to drop 32-bit KVM support for now
> - Drop patch for 64-bit Silverlake support
> - Drop 64-bit ISA level selection, only fix default
> - Rework MID patch based on comments
> - Add a patch to reorganize platform selection
> - Add a patch to add -march=native compilation
>
>
> Arnd Bergmann (10):
> x86/Kconfig: Geode CPU has cmpxchg8b
> x86: drop 32-bit "bigsmp" machine support
> x86: rework CONFIG_GENERIC_CPU compiler flags
> x86: drop configuration options for early 64-bit CPUs
> x86: remove HIGHMEM64G support
> x86: drop SWIOTLB for PAE
> x86: drop support for CONFIG_HIGHPTE
> x86: document X86_INTEL_MID as 64-bit-only
> x86: remove old STA2x11 support
> x86: only allow EISA for 32-bit
>
> Documentation/admin-guide/kdump/kdump.rst | 4 -
> .../admin-guide/kernel-parameters.txt | 11 -
> Documentation/arch/x86/usb-legacy-support.rst | 11 +-
> arch/x86/Kconfig | 156 +++---------
> arch/x86/Kconfig.cpu | 97 ++------
> arch/x86/Makefile | 16 +-
> arch/x86/Makefile_32.cpu | 5 +-
> arch/x86/configs/xen.config | 2 -
> arch/x86/include/asm/page_32_types.h | 4 +-
> arch/x86/include/asm/pgalloc.h | 5 -
> arch/x86/include/asm/sta2x11.h | 13 -
> arch/x86/include/asm/vermagic.h | 4 -
> arch/x86/kernel/apic/Makefile | 3 -
> arch/x86/kernel/apic/apic.c | 3 -
> arch/x86/kernel/apic/bigsmp_32.c | 105 --------
> arch/x86/kernel/apic/local.h | 13 -
> arch/x86/kernel/apic/probe_32.c | 29 ---
> arch/x86/mm/init_32.c | 9 +-
> arch/x86/mm/pgtable.c | 27 +-
> arch/x86/pci/Makefile | 2 -
> arch/x86/pci/sta2x11-fixup.c | 233 ------------------
> drivers/misc/mei/Kconfig | 2 +-
> 22 files changed, 66 insertions(+), 688 deletions(-)

Sweet! I have applied your series to tip:x86/cpu with some minor tweaks
and a conflict resolution for pending work in x86/mm. Let's see if
anyone complains about the removal of these obsolete features.

Thanks,

Ingo