[RFC PATCH 01/12] arch: Add ARCH_HAS_KERNEL_FPU_SUPPORT
From: Samuel Holland <samuel.holland@sifive.com>
Date: 2023-12-08 05:55:11
Also in:
amd-gfx, linux-arch, linux-riscv, linuxppc-dev, lkml, loongarch
Subsystem:
kernel build + files below scripts/ (unless maintained elsewhere), the rest · Maintainers:
Nathan Chancellor, Nicolas Schier, Linus Torvalds
Several architectures provide an API to enable the FPU and run floating-point SIMD code in kernel space. However, the function names, header locations, and semantics are inconsistent across architectures, and FPU support may be gated behind other Kconfig options. Provide a standard way for architectures to declare that kernel space FPU support is available. Architectures selecting this option must implement what is currently the most common API (kernel_fpu_begin() and kernel_fpu_end(), plus a new function kernel_fpu_available()) and provide the appropriate CFLAGS for compiling floating-point C code. Suggested-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> --- Makefile | 4 ++++ arch/Kconfig | 9 +++++++++ 2 files changed, 13 insertions(+)
diff --git a/Makefile b/Makefile
index 511b5616aa41..e65c186cf2c9 100644
--- a/Makefile
+++ b/Makefile@@ -969,6 +969,10 @@ KBUILD_CFLAGS += $(CC_FLAGS_CFI) export CC_FLAGS_CFI endif +# Architectures can define flags to add/remove for floating-point support +export CC_FLAGS_FPU +export CC_FLAGS_NO_FPU + ifneq ($(CONFIG_FUNCTION_ALIGNMENT),0) KBUILD_CFLAGS += -falign-functions=$(CONFIG_FUNCTION_ALIGNMENT) endif
diff --git a/arch/Kconfig b/arch/Kconfig
index f4b210ab0612..6df834e18e9c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig@@ -1478,6 +1478,15 @@ config ARCH_HAS_NONLEAF_PMD_YOUNG address translations. Page table walkers that clear the accessed bit may use this capability to reduce their search space. +config ARCH_HAS_KERNEL_FPU_SUPPORT + bool + help + An architecture should select this option if it supports running + floating-point code in kernel space. It must export the functions + kernel_fpu_available(), kernel_fpu_begin(), and kernel_fpu_end() from + <asm/fpu.h>, and define CC_FLAGS_FPU and/or CC_FLAGS_NO_FPU as + necessary in its Makefile. + source "kernel/gcov/Kconfig" source "scripts/gcc-plugins/Kconfig"
--
2.42.0
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