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Add the CONFIG_X86_NATIVE_CPU=y build option to locally optimize the kernel

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build with '-march=native'.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-build-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 build updates from Ingo Molnar:
 "Add the CONFIG_X86_NATIVE_CPU=y build option to locally optimize the
  kernel build with '-march=native'"

* tag 'x86-build-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/kbuild/64: Restrict clang versions that can use '-march=native'
  x86/kbuild/64: Test for the availability of the -mtune=native compiler flag
  x86/kbuild/64: Add the CONFIG_X86_NATIVE_CPU option to locally optimize the kernel with '-march=native'
This commit is contained in:
Linus Torvalds 2025-05-26 21:41:14 -07:00
commit 914873bc7d
2 changed files with 29 additions and 0 deletions
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24
arch/x86/Kconfig.cpu
View file

@ -245,6 +245,30 @@ config MATOM
endchoice
config CC_HAS_MARCH_NATIVE
# This flag might not be available in cross-compilers:
def_bool $(cc-option, -march=native)
# LLVM 18 has an easily triggered internal compiler error in core
# networking code with '-march=native' on certain systems:
# https://github.com/llvm/llvm-project/issues/72026
# LLVM 19 introduces an optimization that resolves some high stack
# usage warnings that only appear wth '-march=native'.
depends on CC_IS_GCC || CLANG_VERSION >= 190100
config X86_NATIVE_CPU
bool "Build and optimize for local/native CPU"
depends on X86_64
depends on CC_HAS_MARCH_NATIVE
help
Optimize for the current CPU used to compile the kernel.
Use this option if you intend to build the kernel for your
local machine.
Note that such a kernel might not work optimally on a
different x86 machine.
If unsure, say N.
config X86_GENERIC
bool "Generic x86 support"
depends on X86_32

5
arch/x86/Makefile
View file

@ -173,8 +173,13 @@ else
# Use -mskip-rax-setup if supported.
KBUILD_CFLAGS += $(call cc-option,-mskip-rax-setup)
ifdef CONFIG_X86_NATIVE_CPU
KBUILD_CFLAGS += -march=native
KBUILD_RUSTFLAGS += -Ctarget-cpu=native
else
KBUILD_CFLAGS += -march=x86-64 -mtune=generic
KBUILD_RUSTFLAGS += -Ctarget-cpu=x86-64 -Ztune-cpu=generic
endif
KBUILD_CFLAGS += -mno-red-zone
KBUILD_CFLAGS += -mcmodel=kernel