From: Samuel Holland <samuel.holland@sifive.com>
To: Andrew Morton <akpm@linux-foundation.org>,
linux-arm-kernel@lists.infradead.org, x86@kernel.org
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
Christoph Hellwig <hch@lst.de>,
loongarch@lists.linux.dev, amd-gfx@lists.freedesktop.org,
Samuel Holland <samuel.holland@sifive.com>,
Palmer Dabbelt <palmer@rivosinc.com>
Subject: [PATCH v4 11/15] riscv: Add support for kernel-mode FPU
Date: Fri, 29 Mar 2024 00:18:26 -0700 [thread overview]
Message-ID: <20240329072441.591471-12-samuel.holland@sifive.com> (raw)
In-Reply-To: <20240329072441.591471-1-samuel.holland@sifive.com>
This is motivated by the amdgpu DRM driver, which needs floating-point
code to support recent hardware. That code is not performance-critical,
so only provide a minimal non-preemptible implementation for now.
Support is limited to riscv64 because riscv32 requires runtime (libgcc)
assistance to convert between doubles and 64-bit integers.
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---
(no changes since v3)
Changes in v3:
- Limit riscv ARCH_HAS_KERNEL_FPU_SUPPORT to 64BIT
Changes in v2:
- Remove RISC-V architecture-specific preprocessor check
arch/riscv/Kconfig | 1 +
arch/riscv/Makefile | 3 +++
arch/riscv/include/asm/fpu.h | 16 ++++++++++++++++
arch/riscv/kernel/Makefile | 1 +
arch/riscv/kernel/kernel_mode_fpu.c | 28 ++++++++++++++++++++++++++++
5 files changed, 49 insertions(+)
create mode 100644 arch/riscv/include/asm/fpu.h
create mode 100644 arch/riscv/kernel/kernel_mode_fpu.c
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index be09c8836d56..3bcd0d250810 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -27,6 +27,7 @@ config RISCV
select ARCH_HAS_GCOV_PROFILE_ALL
select ARCH_HAS_GIGANTIC_PAGE
select ARCH_HAS_KCOV
+ select ARCH_HAS_KERNEL_FPU_SUPPORT if 64BIT && FPU
select ARCH_HAS_MEMBARRIER_CALLBACKS
select ARCH_HAS_MEMBARRIER_SYNC_CORE
select ARCH_HAS_MMIOWB
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 252d63942f34..76ff4033c854 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -84,6 +84,9 @@ KBUILD_CFLAGS += -march=$(shell echo $(riscv-march-y) | sed -E 's/(rv32ima|rv64i
KBUILD_AFLAGS += -march=$(riscv-march-y)
+# For C code built with floating-point support, exclude V but keep F and D.
+CC_FLAGS_FPU := -march=$(shell echo $(riscv-march-y) | sed -E 's/(rv32ima|rv64ima)([^v_]*)v?/\1\2/')
+
KBUILD_CFLAGS += -mno-save-restore
KBUILD_CFLAGS += -DCONFIG_PAGE_OFFSET=$(CONFIG_PAGE_OFFSET)
diff --git a/arch/riscv/include/asm/fpu.h b/arch/riscv/include/asm/fpu.h
new file mode 100644
index 000000000000..91c04c244e12
--- /dev/null
+++ b/arch/riscv/include/asm/fpu.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2023 SiFive
+ */
+
+#ifndef _ASM_RISCV_FPU_H
+#define _ASM_RISCV_FPU_H
+
+#include <asm/switch_to.h>
+
+#define kernel_fpu_available() has_fpu()
+
+void kernel_fpu_begin(void);
+void kernel_fpu_end(void);
+
+#endif /* ! _ASM_RISCV_FPU_H */
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 81d94a8ee10f..5b243d46f4b1 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -67,6 +67,7 @@ obj-$(CONFIG_RISCV_MISALIGNED) += unaligned_access_speed.o
obj-$(CONFIG_RISCV_PROBE_UNALIGNED_ACCESS) += copy-unaligned.o
obj-$(CONFIG_FPU) += fpu.o
+obj-$(CONFIG_FPU) += kernel_mode_fpu.o
obj-$(CONFIG_RISCV_ISA_V) += vector.o
obj-$(CONFIG_RISCV_ISA_V) += kernel_mode_vector.o
obj-$(CONFIG_SMP) += smpboot.o
diff --git a/arch/riscv/kernel/kernel_mode_fpu.c b/arch/riscv/kernel/kernel_mode_fpu.c
new file mode 100644
index 000000000000..0ac8348876c4
--- /dev/null
+++ b/arch/riscv/kernel/kernel_mode_fpu.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023 SiFive
+ */
+
+#include <linux/export.h>
+#include <linux/preempt.h>
+
+#include <asm/csr.h>
+#include <asm/fpu.h>
+#include <asm/processor.h>
+#include <asm/switch_to.h>
+
+void kernel_fpu_begin(void)
+{
+ preempt_disable();
+ fstate_save(current, task_pt_regs(current));
+ csr_set(CSR_SSTATUS, SR_FS);
+}
+EXPORT_SYMBOL_GPL(kernel_fpu_begin);
+
+void kernel_fpu_end(void)
+{
+ csr_clear(CSR_SSTATUS, SR_FS);
+ fstate_restore(current, task_pt_regs(current));
+ preempt_enable();
+}
+EXPORT_SYMBOL_GPL(kernel_fpu_end);
--
2.44.0
next prev parent reply other threads:[~2024-03-29 7:25 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-29 7:18 [PATCH v4 00/15] Unified cross-architecture kernel-mode FPU API Samuel Holland
2024-03-29 7:18 ` [PATCH v4 01/15] arch: Add ARCH_HAS_KERNEL_FPU_SUPPORT Samuel Holland
2024-03-29 7:18 ` [PATCH v4 02/15] ARM: Implement ARCH_HAS_KERNEL_FPU_SUPPORT Samuel Holland
2024-03-29 7:18 ` [PATCH v4 03/15] ARM: crypto: Use CC_FLAGS_FPU for NEON CFLAGS Samuel Holland
2024-03-29 7:18 ` [PATCH v4 04/15] arm64: Implement ARCH_HAS_KERNEL_FPU_SUPPORT Samuel Holland
2024-03-29 7:18 ` [PATCH v4 05/15] arm64: crypto: Use CC_FLAGS_FPU for NEON CFLAGS Samuel Holland
2024-03-29 7:18 ` [PATCH v4 06/15] lib/raid6: " Samuel Holland
2024-03-29 7:18 ` [PATCH v4 07/15] LoongArch: Implement ARCH_HAS_KERNEL_FPU_SUPPORT Samuel Holland
2024-03-29 7:18 ` [PATCH v4 08/15] powerpc: " Samuel Holland
2024-03-29 7:18 ` [PATCH v4 09/15] x86/fpu: Fix asm/fpu/types.h include guard Samuel Holland
2024-03-29 17:30 ` Dave Hansen
2024-03-29 7:18 ` [PATCH v4 10/15] x86: Implement ARCH_HAS_KERNEL_FPU_SUPPORT Samuel Holland
2024-03-29 17:28 ` Dave Hansen
2024-03-29 18:02 ` Samuel Holland
2024-03-29 7:18 ` Samuel Holland [this message]
2024-03-29 7:18 ` [PATCH v4 12/15] drm/amd/display: Only use hard-float, not altivec on powerpc Samuel Holland
2024-04-30 17:28 ` Harry Wentland
2024-03-29 7:18 ` [PATCH v4 13/15] drm/amd/display: Use ARCH_HAS_KERNEL_FPU_SUPPORT Samuel Holland
2024-04-10 22:21 ` Thiago Jung Bauermann
2024-04-10 22:47 ` Samuel Holland
2024-04-11 1:02 ` Thiago Jung Bauermann
2024-04-11 1:11 ` Samuel Holland
2024-04-11 1:27 ` Thiago Jung Bauermann
2024-04-11 7:15 ` Ard Biesheuvel
2024-04-11 7:31 ` Arnd Bergmann
2024-04-12 1:54 ` Dave Airlie
2024-04-30 17:29 ` Harry Wentland
2024-05-24 4:50 ` Guenter Roeck
2024-05-24 13:17 ` Alex Deucher
2024-05-24 13:18 ` Alex Deucher
2024-05-24 13:43 ` Guenter Roeck
2024-05-24 13:53 ` Guenter Roeck
2024-05-24 18:23 ` Guenter Roeck
2024-03-29 7:18 ` [PATCH v4 14/15] selftests/fpu: Move FP code to a separate translation unit Samuel Holland
2024-03-29 7:18 ` [PATCH v4 15/15] selftests/fpu: Allow building on other architectures Samuel Holland
2024-04-03 12:51 ` [PATCH v4 00/15] Unified cross-architecture kernel-mode FPU API Christian König
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