The patch titled
Subject: x86: implement ARCH_HAS_KERNEL_FPU_SUPPORT
has been added to the -mm mm-nonmm-unstable branch. Its filename is
x86-implement-arch_has_kernel_fpu_support.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/x86-implement-arch_has_kernel_fpu_support.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Samuel Holland <samuel.holland@xxxxxxxxxx>
Subject: x86: implement ARCH_HAS_KERNEL_FPU_SUPPORT
Date: Fri, 29 Mar 2024 00:18:25 -0700
x86 already provides kernel_fpu_begin() and kernel_fpu_end(), but in a
different header. Add a wrapper header, and export the CFLAGS adjustments
as found in lib/Makefile.
Link: https://lkml.kernel.org/r/20240329072441.591471-11-samuel.holland@xxxxxxxxxx
Signed-off-by: Samuel Holland <samuel.holland@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Huacai Chen <chenhuacai@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: Nicolas Schier <nicolas@xxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: WANG Xuerui <git@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/Kconfig | 1 +
arch/x86/Makefile | 20 ++++++++++++++++++++
arch/x86/include/asm/fpu.h | 13 +++++++++++++
3 files changed, 34 insertions(+)
--- /dev/null
+++ a/arch/x86/include/asm/fpu.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2023 SiFive
+ */
+
+#ifndef _ASM_X86_FPU_H
+#define _ASM_X86_FPU_H
+
+#include <asm/fpu/api.h>
+
+#define kernel_fpu_available() true
+
+#endif /* ! _ASM_X86_FPU_H */
--- a/arch/x86/Kconfig~x86-implement-arch_has_kernel_fpu_support
+++ a/arch/x86/Kconfig
@@ -83,6 +83,7 @@ config X86
select ARCH_HAS_FORTIFY_SOURCE
select ARCH_HAS_GCOV_PROFILE_ALL
select ARCH_HAS_KCOV if X86_64
+ select ARCH_HAS_KERNEL_FPU_SUPPORT
select ARCH_HAS_MEM_ENCRYPT
select ARCH_HAS_MEMBARRIER_SYNC_CORE
select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
--- a/arch/x86/Makefile~x86-implement-arch_has_kernel_fpu_support
+++ a/arch/x86/Makefile
@@ -74,6 +74,26 @@ KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-
KBUILD_RUSTFLAGS += --target=$(objtree)/scripts/target.json
KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2
+#
+# CFLAGS for compiling floating point code inside the kernel.
+#
+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)
#
# Kernel IBT has S_CET.NOTRACK_EN=0, as such the compilers must not generate
_
Patches currently in -mm which might be from samuel.holland@xxxxxxxxxx are
x86-fpu-fix-asm-fpu-typesh-include-guard.patch
arch-add-arch_has_kernel_fpu_support.patch
arm-implement-arch_has_kernel_fpu_support.patch
arm-crypto-use-cc_flags_fpu-for-neon-cflags.patch
arm64-implement-arch_has_kernel_fpu_support.patch
arm64-crypto-use-cc_flags_fpu-for-neon-cflags.patch
lib-raid6-use-cc_flags_fpu-for-neon-cflags.patch
loongarch-implement-arch_has_kernel_fpu_support.patch
powerpc-implement-arch_has_kernel_fpu_support.patch
x86-implement-arch_has_kernel_fpu_support.patch
riscv-add-support-for-kernel-mode-fpu.patch
drm-amd-display-use-arch_has_kernel_fpu_support.patch
selftests-fpu-move-fp-code-to-a-separate-translation-unit.patch
selftests-fpu-allow-building-on-other-architectures.patch
