Messages in this thread Patch in this message | | | From | Heiko Stuebner <> | Subject | [PATCH RFC 01/12] riscv: Add support for kernel mode vector | Date | Mon, 6 Feb 2023 23:58:35 +0100 |
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From: Greentime Hu <greentime.hu@sifive.com>
Add kernel_rvv_begin() and kernel_rvv_end() function declarations and corresponding definitions in kernel_mode_vector.c
These are needed to wrap uses of vector in kernel mode.
Co-developed-by: Vincent Chen <vincent.chen@sifive.com> Signed-off-by: Vincent Chen <vincent.chen@sifive.com> Signed-off-by: Greentime Hu <greentime.hu@sifive.com> Signed-off-by: Heiko Stuebner <heiko.stuebner@vrull.eu> --- arch/riscv/include/asm/vector.h | 14 +++ arch/riscv/kernel/Makefile | 1 + arch/riscv/kernel/kernel_mode_vector.c | 132 +++++++++++++++++++++++++ 3 files changed, 147 insertions(+) create mode 100644 arch/riscv/kernel/kernel_mode_vector.c
diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h index 7c77696d704a..f38266ec483a 100644 --- a/arch/riscv/include/asm/vector.h +++ b/arch/riscv/include/asm/vector.h @@ -134,6 +134,20 @@ static inline void vstate_restore(struct task_struct *task, } } +static inline void vector_flush_cpu_state(void) +{ + asm volatile ( + "vsetvli t0, x0, e8, m8, ta, ma\n\t" + "vmv.v.i v0, 0\n\t" + "vmv.v.i v8, 0\n\t" + "vmv.v.i v16, 0\n\t" + "vmv.v.i v24, 0\n\t" + : : : "t0"); +} + +void kernel_rvv_begin(void); +void kernel_rvv_end(void); + #else /* ! CONFIG_RISCV_ISA_V */ struct pt_regs; diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile index 48d345a5f326..304c500cc1f7 100644 --- a/arch/riscv/kernel/Makefile +++ b/arch/riscv/kernel/Makefile @@ -56,6 +56,7 @@ obj-$(CONFIG_MMU) += vdso.o vdso/ obj-$(CONFIG_RISCV_M_MODE) += traps_misaligned.o obj-$(CONFIG_FPU) += fpu.o obj-$(CONFIG_RISCV_ISA_V) += vector.o +obj-$(CONFIG_RISCV_ISA_V) += kernel_mode_vector.o obj-$(CONFIG_SMP) += smpboot.o obj-$(CONFIG_SMP) += smp.o obj-$(CONFIG_SMP) += cpu_ops.o diff --git a/arch/riscv/kernel/kernel_mode_vector.c b/arch/riscv/kernel/kernel_mode_vector.c new file mode 100644 index 000000000000..0277168af0c5 --- /dev/null +++ b/arch/riscv/kernel/kernel_mode_vector.c @@ -0,0 +1,132 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2012 ARM Ltd. + * Author: Catalin Marinas <catalin.marinas@arm.com> + * Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org> + * Copyright (C) 2021 SiFive + */ +#include <linux/compiler.h> +#include <linux/irqflags.h> +#include <linux/percpu.h> +#include <linux/preempt.h> +#include <linux/types.h> + +#include <asm/vector.h> +#include <asm/switch_to.h> + +DECLARE_PER_CPU(bool, vector_context_busy); +DEFINE_PER_CPU(bool, vector_context_busy); + +/* + * may_use_vector - whether it is allowable at this time to issue vector + * instructions or access the vector register file + * + * Callers must not assume that the result remains true beyond the next + * preempt_enable() or return from softirq context. + */ +static __must_check inline bool may_use_vector(void) +{ + /* + * vector_context_busy is only set while preemption is disabled, + * and is clear whenever preemption is enabled. Since + * this_cpu_read() is atomic w.r.t. preemption, vector_context_busy + * cannot change under our feet -- if it's set we cannot be + * migrated, and if it's clear we cannot be migrated to a CPU + * where it is set. + */ + return !in_irq() && !irqs_disabled() && !in_nmi() && + !this_cpu_read(vector_context_busy); +} + +/* + * Claim ownership of the CPU vector context for use by the calling context. + * + * The caller may freely manipulate the vector context metadata until + * put_cpu_vector_context() is called. + */ +static void get_cpu_vector_context(void) +{ + bool busy; + + preempt_disable(); + busy = __this_cpu_xchg(vector_context_busy, true); + + WARN_ON(busy); +} + +/* + * Release the CPU vector context. + * + * Must be called from a context in which get_cpu_vector_context() was + * previously called, with no call to put_cpu_vector_context() in the + * meantime. + */ +static void put_cpu_vector_context(void) +{ + bool busy = __this_cpu_xchg(vector_context_busy, false); + + WARN_ON(!busy); + preempt_enable(); +} + +/* + * kernel_rvv_begin(): obtain the CPU vector registers for use by the calling + * context + * + * Must not be called unless may_use_vector() returns true. + * Task context in the vector registers is saved back to memory as necessary. + * + * A matching call to kernel_rvv_end() must be made before returning from the + * calling context. + * + * The caller may freely use the vector registers until kernel_rvv_end() is + * called. + */ +void kernel_rvv_begin(void) +{ + if (WARN_ON(!has_vector())) + return; + + WARN_ON(!may_use_vector()); + + /* Acquire kernel mode vector */ + get_cpu_vector_context(); + + /* Save vector state, if any */ + vstate_save(current, task_pt_regs(current)); + + /* Enable vector */ + rvv_enable(); + + /* Invalidate vector regs */ + vector_flush_cpu_state(); +} +EXPORT_SYMBOL_GPL(kernel_rvv_begin); + +/* + * kernel_rvv_end(): give the CPU vector registers back to the current task + * + * Must be called from a context in which kernel_rvv_begin() was previously + * called, with no call to kernel_rvv_end() in the meantime. + * + * The caller must not use the vector registers after this function is called, + * unless kernel_rvv_begin() is called again in the meantime. + */ +void kernel_rvv_end(void) +{ + if (WARN_ON(!has_vector())) + return; + + /* Invalidate vector regs */ + vector_flush_cpu_state(); + + /* Restore vector state, if any */ + vstate_restore(current, task_pt_regs(current)); + + /* disable vector */ + rvv_disable(); + + /* release kernel mode vector */ + put_cpu_vector_context(); +} +EXPORT_SYMBOL_GPL(kernel_rvv_end); -- 2.39.0
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