linux-kernel - [PATCH 3/6] x86/build: Clean up stack alignment flags in CC_FLAGS

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Message-Id: <20250814-x86-min-ver-cleanups-v1-3-ff7f19457523@kernel.org>
Date: Thu, 14 Aug 2025 18:31:39 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
 x86@...nel.org
Cc: linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, 
 patches@...ts.linux.dev, Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH 3/6] x86/build: Clean up stack alignment flags in
 CC_FLAGS_FPU

The minimum supported version of GCC to build the x86 kernel was bumped
to GCC 8.1 in commit a3e8fe814ad1 ("x86/build: Raise the minimum GCC
version to 8.1").

Prior to GCC 7.1, '-mpreferred-stack-boundary=3' was not allowed with
'-msse', so areas of the kernel that needed floating point had a
different alignment. Now that GCC > 7.1 is mandatory, there is no need
to have a different value of '-mpreferred-stack-boundary' from the rest
of the kernel, so remove this handling from CC_FLAGS_FPU.

Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=34fac449e121be97dd073c5428cc855367b2872c
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 arch/x86/Makefile | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index f0aa58d2ec17..0c82a610fb54 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -84,19 +84,7 @@ KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-av
 #
 CC_FLAGS_FPU := -msse -msse2
 ifdef CONFIG_CC_IS_GCC
-# Stack alignment mismatch, proceed with caution.
-# GCC < 7.1 cannot compile code using `double` and -mpreferred-stack-boundary=3
-# (8B stack alignment).
-# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
-#
-# The "-msse" in the first argument is there so that the
-# -mpreferred-stack-boundary=3 build error:
-#
-#  -mpreferred-stack-boundary=3 is not between 4 and 12
-#
-# can be triggered. Otherwise gcc doesn't complain.
 CC_FLAGS_FPU += -mhard-float
-CC_FLAGS_FPU += $(call cc-option,-msse -mpreferred-stack-boundary=3,-mpreferred-stack-boundary=4)
 endif
 
 ifeq ($(CONFIG_X86_KERNEL_IBT),y)

-- 
2.50.1