[PATCH v4 10/15] x86: Implement ARCH_HAS_KERNEL_FPU_SUPPORT
From: Samuel Holland <samuel.holland@sifive.com>
Date: 2024-03-29 07:25:02
Also in:
amd-gfx, linux-arch, linux-arm-kernel, linux-riscv, lkml, loongarch
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> --- (no changes since v1) arch/x86/Kconfig | 1 + arch/x86/Makefile | 20 ++++++++++++++++++++ arch/x86/include/asm/fpu.h | 13 +++++++++++++ 3 files changed, 34 insertions(+) create mode 100644 arch/x86/include/asm/fpu.h
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 39886bab943a..7c9d032ee675 100644
--- a/arch/x86/Kconfig
+++ b/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
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 662d9d4033e6..5a5f5999c505 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile@@ -74,6 +74,26 @@ KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx 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
diff --git a/arch/x86/include/asm/fpu.h b/arch/x86/include/asm/fpu.h
new file mode 100644
index 000000000000..b2743fe19339
--- /dev/null
+++ b/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 */
--
2.44.0