Backport patches from upstream so we can use LSX/LASX in the kernel.
Huacai Chen (2): LoongArch: Provide kernel fpu functions LoongArch: Allow usage of LSX/LASX in the kernel
arch/loongarch/include/asm/fpu.h | 3 ++ arch/loongarch/kernel/Makefile | 2 +- arch/loongarch/kernel/kfpu.c | 90 ++++++++++++++++++++++++++++++++ 3 files changed, 94 insertions(+), 1 deletion(-) create mode 100644 arch/loongarch/kernel/kfpu.c
From: Huacai Chen chenhuacai@loongson.cn
LoongArch inclusion bugzilla: https://gitee.com/openeuler/kernel/issues/I76XQZ
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@xen0n.name Tested-by: WANG Xuerui kernel@xen0n.name Signed-off-by: Huacai Chen chenhuacai@loongson.cn --- arch/loongarch/include/asm/fpu.h | 3 +++ arch/loongarch/kernel/Makefile | 2 +- arch/loongarch/kernel/kfpu.c | 43 ++++++++++++++++++++++++++++++++ 3 files changed, 47 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 1363f92929df..67a95d737f85 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 3afde226091f..5420904faf52 100644 --- a/arch/loongarch/kernel/Makefile +++ b/arch/loongarch/kernel/Makefile @@ -13,7 +13,7 @@ obj-y += 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-$(CONFIG_MODULES) += module.o module-sections.o obj-$(CONFIG_STACKTRACE) += stacktrace.o diff --git a/arch/loongarch/kernel/kfpu.c b/arch/loongarch/kernel/kfpu.c new file mode 100644 index 000000000000..5c46ae8c6cac --- /dev/null +++ b/arch/loongarch/kernel/kfpu.c @@ -0,0 +1,43 @@ +// 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) +{ + preempt_disable(); + + WARN_ON(this_cpu_read(in_kernel_fpu)); + + this_cpu_write(in_kernel_fpu, true); + + if (!is_fpu_owner()) + enable_fpu(); + else + _save_fp(¤t->thread.fpu); + + write_fcsr(LOONGARCH_FCSR0, 0); +} +EXPORT_SYMBOL_GPL(kernel_fpu_begin); + +void kernel_fpu_end(void) +{ + WARN_ON(!this_cpu_read(in_kernel_fpu)); + + if (!is_fpu_owner()) + disable_fpu(); + else + _restore_fp(¤t->thread.fpu); + + this_cpu_write(in_kernel_fpu, false); + + preempt_enable(); +} +EXPORT_SYMBOL_GPL(kernel_fpu_end);
From: Huacai Chen chenhuacai@loongson.cn
LoongArch inclusion bugzilla: https://gitee.com/openeuler/kernel/issues/I76XQZ
Allow usage of LSX/LASX in the kernel by extending kernel_fpu_begin() and kernel_fpu_end().
Reviewed-by: WANG Xuerui git@xen0n.name Signed-off-by: Huacai Chen chenhuacai@loongson.cn --- arch/loongarch/kernel/kfpu.c | 55 +++++++++++++++++++++++++++++++++--- 1 file changed, 51 insertions(+), 4 deletions(-)
diff --git a/arch/loongarch/kernel/kfpu.c b/arch/loongarch/kernel/kfpu.c index 5c46ae8c6cac..ec5b28e570c9 100644 --- a/arch/loongarch/kernel/kfpu.c +++ b/arch/loongarch/kernel/kfpu.c @@ -8,19 +8,40 @@ #include <asm/fpu.h> #include <asm/smp.h>
+static unsigned int euen_mask = CSR_EUEN_FPEN; + +/* + * The critical section between kernel_fpu_begin() and kernel_fpu_end() + * is non-reentrant. It is the caller's responsibility to avoid reentrance. + * See drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c as an example. + */ static DEFINE_PER_CPU(bool, in_kernel_fpu); +static DEFINE_PER_CPU(unsigned int, euen_current);
void kernel_fpu_begin(void) { + unsigned int *euen_curr; + preempt_disable();
WARN_ON(this_cpu_read(in_kernel_fpu));
this_cpu_write(in_kernel_fpu, true); + euen_curr = this_cpu_ptr(&euen_current);
- if (!is_fpu_owner()) - enable_fpu(); + *euen_curr = csr_xchg32(euen_mask, euen_mask, LOONGARCH_CSR_EUEN); + +#ifdef CONFIG_CPU_HAS_LASX + if (*euen_curr & CSR_EUEN_LASXEN) + _save_lasx(¤t->thread.fpu); + else +#endif +#ifdef CONFIG_CPU_HAS_LSX + if (*euen_curr & CSR_EUEN_LSXEN) + _save_lsx(¤t->thread.fpu); else +#endif + if (*euen_curr & CSR_EUEN_FPEN) _save_fp(¤t->thread.fpu);
write_fcsr(LOONGARCH_FCSR0, 0); @@ -29,15 +50,41 @@ EXPORT_SYMBOL_GPL(kernel_fpu_begin);
void kernel_fpu_end(void) { + unsigned int *euen_curr; + WARN_ON(!this_cpu_read(in_kernel_fpu));
- if (!is_fpu_owner()) - disable_fpu(); + euen_curr = this_cpu_ptr(&euen_current); + +#ifdef CONFIG_CPU_HAS_LASX + if (*euen_curr & CSR_EUEN_LASXEN) + _restore_lasx(¤t->thread.fpu); else +#endif +#ifdef CONFIG_CPU_HAS_LSX + if (*euen_curr & CSR_EUEN_LSXEN) + _restore_lsx(¤t->thread.fpu); + else +#endif + if (*euen_curr & CSR_EUEN_FPEN) _restore_fp(¤t->thread.fpu);
+ *euen_curr = csr_xchg32(*euen_curr, euen_mask, LOONGARCH_CSR_EUEN); + this_cpu_write(in_kernel_fpu, false);
preempt_enable(); } EXPORT_SYMBOL_GPL(kernel_fpu_end); + +static int __init init_euen_mask(void) +{ + if (cpu_has_lsx) + euen_mask |= CSR_EUEN_LSXEN; + + if (cpu_has_lasx) + euen_mask |= CSR_EUEN_LASXEN; + + return 0; +} +arch_initcall(init_euen_mask);
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