diff mbox series

[RFC,01/12] arch: Add ARCH_HAS_KERNEL_FPU_SUPPORT

Message ID	20231208055501.2916202-2-samuel.holland@sifive.com
State	New
Headers	Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.33 as permitted sender) client-ip=23.128.96.33; From: Samuel Holland <samuel.holland@sifive.com> To: linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-riscv@lists.infradead.org, Christoph Hellwig <hch@infradead.org> Cc: linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, linux-arch@vger.kernel.org, Samuel Holland <samuel.holland@sifive.com> Subject: [RFC PATCH 01/12] arch: Add ARCH_HAS_KERNEL_FPU_SUPPORT Date: Thu, 7 Dec 2023 21:54:31 -0800 Message-ID: <20231208055501.2916202-2-samuel.holland@sifive.com> In-Reply-To: <20231208055501.2916202-1-samuel.holland@sifive.com> References: <20231208055501.2916202-1-samuel.holland@sifive.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk
Series	Unified cross-architecture kernel-mode FPU API \| [RFC,00/12] Unified cross-architecture kernel-mode FPU API [RFC,01/12] arch: Add ARCH_HAS_KERNEL_FPU_SUPPORT [RFC,02/12] ARM: Implement ARCH_HAS_KERNEL_FPU_SUPPORT [RFC,03/12] ARM: crypto: Use CC_FLAGS_FPU for NEON CFLAGS [RFC,04/12] arm64: Implement ARCH_HAS_KERNEL_FPU_SUPPORT [RFC,05/12] lib/raid6: Use CC_FLAGS_FPU for NEON CFLAGS [RFC,06/12] LoongArch: Implement ARCH_HAS_KERNEL_FPU_SUPPORT [RFC,07/12] powerpc: Implement ARCH_HAS_KERNEL_FPU_SUPPORT [RFC,08/12] x86: Implement ARCH_HAS_KERNEL_FPU_SUPPORT [RFC,09/12] riscv: Add support for kernel-mode FPU [RFC,10/12] drm/amd/display: Use ARCH_HAS_KERNEL_FPU_SUPPORT [RFC,11/12] selftests/fpu: Move FP code to a separate translation unit [RFC,12/12] selftests/fpu: Allow building on other architectures

Commit Message

Samuel Holland Dec. 8, 2023, 5:54 a.m. UTC

  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(+)

Comments

Christoph Hellwig Dec. 11, 2023, 4:02 p.m. UTC | #1

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

diff mbox series

Patch

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"