[PATCH V3] LoongArch: Provide kernel fpu functions

From: Huacai Chen
Date: Mon Mar 06 2023 - 05:00:10 EST


Provide kernel_fpu_begin()/kernel_fpu_end() to allow the kernel itself
to use fpu. They can be used by some other kernel components, e.g., the
AMDGPU graphic driver for DCN.

Reported-by: WANG Xuerui <kernel@xxxxxxxxxx>
Tested-by: WANG Xuerui <kernel@xxxxxxxxxx>
Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
---
V2: Use non-GPL exports and update commit messages.
V3: Add spaces for coding style.

arch/loongarch/include/asm/fpu.h | 3 +++
arch/loongarch/kernel/Makefile | 2 +-
arch/loongarch/kernel/kfpu.c | 41 ++++++++++++++++++++++++++++++++
3 files changed, 45 insertions(+), 1 deletion(-)
create mode 100644 arch/loongarch/kernel/kfpu.c

diff --git a/arch/loongarch/include/asm/fpu.h b/arch/loongarch/include/asm/fpu.h
index 358b254d9c1d..192f8e35d912 100644
--- a/arch/loongarch/include/asm/fpu.h
+++ b/arch/loongarch/include/asm/fpu.h
@@ -21,6 +21,9 @@

struct sigcontext;

+extern void kernel_fpu_begin(void);
+extern void kernel_fpu_end(void);
+
extern void _init_fpu(unsigned int);
extern void _save_fp(struct loongarch_fpu *);
extern void _restore_fp(struct loongarch_fpu *);
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 78d4e3384305..9a72d91cd104 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -13,7 +13,7 @@ obj-y += head.o cpu-probe.o cacheinfo.o env.o setup.o entry.o genex.o \
obj-$(CONFIG_ACPI) += acpi.o
obj-$(CONFIG_EFI) += efi.o

-obj-$(CONFIG_CPU_HAS_FPU) += fpu.o
+obj-$(CONFIG_CPU_HAS_FPU) += fpu.o kfpu.o

obj-$(CONFIG_ARCH_STRICT_ALIGN) += unaligned.o

diff --git a/arch/loongarch/kernel/kfpu.c b/arch/loongarch/kernel/kfpu.c
new file mode 100644
index 000000000000..cd2a18fecdcc
--- /dev/null
+++ b/arch/loongarch/kernel/kfpu.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023 Loongson Technology Corporation Limited
+ */
+
+#include <linux/cpu.h>
+#include <linux/init.h>
+#include <asm/fpu.h>
+#include <asm/smp.h>
+
+static DEFINE_PER_CPU(bool, in_kernel_fpu);
+
+void kernel_fpu_begin(void)
+{
+ if (this_cpu_read(in_kernel_fpu))
+ return;
+
+ preempt_disable();
+ this_cpu_write(in_kernel_fpu, true);
+
+ if (!is_fpu_owner())
+ enable_fpu();
+ else
+ _save_fp(&current->thread.fpu);
+}
+EXPORT_SYMBOL(kernel_fpu_begin);
+
+void kernel_fpu_end(void)
+{
+ if (!this_cpu_read(in_kernel_fpu))
+ return;
+
+ if (!is_fpu_owner())
+ disable_fpu();
+ else
+ _restore_fp(&current->thread.fpu);
+
+ this_cpu_write(in_kernel_fpu, false);
+ preempt_enable();
+}
+EXPORT_SYMBOL(kernel_fpu_end);
--
2.39.1