From: Peter Zijlstra Date: Mon, 27 Oct 2025 11:40:59 +0000 (+0100) Subject: x86/build: Disable SSE4a X-Git-Tag: v6.18-rc4~4^2~3 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=0d6e9ec80cebf9b378a1d3a01144e576d731c397;p=thirdparty%2Fkernel%2Flinux.git x86/build: Disable SSE4a Leyvi Rose reported that his X86_NATIVE_CPU=y build is failing because our instruction decoder doesn't support SSE4a and the AMDGPU code seems to be generating those with his compiler of choice (CLANG+LTO). Now, our normal build flags disable SSE MMX SSE2 3DNOW AVX, but then CC_FLAGS_FPU re-enable SSE SSE2. Since nothing mentions SSE3 or SSE4, I'm assuming that -msse (or its negative) control all SSE variants -- but why then explicitly enumerate SSE2 ? Anyway, until the instruction decoder gets fixed, explicitly disallow SSE4a (an AMD specific SSE4 extension). Fixes: ea1dcca1de12 ("x86/kbuild/64: Add the CONFIG_X86_NATIVE_CPU option to locally optimize the kernel with '-march=native'") Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov (AMD) Acked-by: Borislav Petkov (AMD) Acked-by: Arisu Tachibana Acked-by: Christian König Acked-by: Harry Wentland Cc: --- diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 4db7e4bf69f5..8fbff3106c56 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -75,7 +75,7 @@ export BITS # # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383 # -KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx +KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -mno-sse4a KBUILD_RUSTFLAGS += --target=$(objtree)/scripts/target.json KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2