The kernel disables all SSE and similar FP/SIMD instructions on x86-based architectures (partly because we shouldn't be using floats in the kernel, and partly to avoid the need for stack alignment, see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383 ) UML does not do the same thing, which isn't in itself a problem, but does add to the list of differences between UML and "normal" x86 builds. In addition, there was a crash bug with LLVM < 15 / rustc < 1.65 when building with SSE, so disabling it fixes rust builds with earlier compiler versions, see: https://github.com/Rust-for-Linux/linux/pull/881 Signed-off-by: David Gow <davidgow@xxxxxxxxxx> --- arch/x86/Makefile.um | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/Makefile.um b/arch/x86/Makefile.um index b3c1ae084180..d2e95d1d4db7 100644 --- a/arch/x86/Makefile.um +++ b/arch/x86/Makefile.um @@ -1,6 +1,12 @@ # SPDX-License-Identifier: GPL-2.0 core-y += arch/x86/crypto/ +# +# Disable SSE and other FP/SIMD instructions to match normal x86 +# +KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx +KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2 + ifeq ($(CONFIG_X86_32),y) START := 0x8048000 -- 2.39.0.314.g84b9a713c41-goog
