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[59.124.168.89]) by smtp.gmail.com with ESMTPSA id fn7-20020a056a002fc700b006cecaff9e29sm9928601pfb.128.2023.12.13.05.13.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 Dec 2023 05:13:49 -0800 (PST) From: Andy Chiu To: linux-riscv@lists.infradead.org, palmer@dabbelt.com Subject: [v4, 1/6] riscv: Add support for kernel mode vector Date: Wed, 13 Dec 2023 13:13:16 +0000 Message-Id: <20231213131321.12862-2-andy.chiu@sifive.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20231213131321.12862-1-andy.chiu@sifive.com> References: <20231213131321.12862-1-andy.chiu@sifive.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231213_051353_723325_36B78C68 X-CRM114-Status: GOOD ( 24.86 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: guoren@linux.alibaba.com, Heiko Stuebner , arnd@arndb.de, Peter Zijlstra , charlie@rivosinc.com, Conor Dooley , =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , Vincent Chen , bjorn@kernel.org, Albert Ou , Guo Ren , Evan Green , Andy Chiu , Paul Walmsley , Jisheng Zhang , greentime.hu@sifive.com, ardb@kernel.org, Sami Tolvanen , Alexandre Ghiti Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Greentime Hu Add kernel_vector_begin() and kernel_vector_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 Signed-off-by: Vincent Chen Signed-off-by: Greentime Hu Signed-off-by: Andy Chiu --- Changelog v4: - Use kernel_v_flags and helpers to track vector context. Thus remove A-b from Cornor. Changelog v3: - Reorder patch 1 to patch 3 to make use of {get,put}_cpu_vector_context later. - Export {get,put}_cpu_vector_context. - Save V context after disabling preemption. (Guo) - Fix a build fail. (Conor) - Remove irqs_disabled() check as it is not needed, fix styling. (Björn) Changelog v2: - 's/kernel_rvv/kernel_vector' and return void in kernel_vector_begin (Conor) - export may_use_simd to include/asm/simd.h --- arch/riscv/include/asm/processor.h | 15 +++- arch/riscv/include/asm/simd.h | 42 ++++++++++++ arch/riscv/include/asm/vector.h | 21 ++++++ arch/riscv/kernel/Makefile | 1 + arch/riscv/kernel/kernel_mode_vector.c | 95 ++++++++++++++++++++++++++ arch/riscv/kernel/process.c | 2 +- 6 files changed, 174 insertions(+), 2 deletions(-) create mode 100644 arch/riscv/include/asm/simd.h create mode 100644 arch/riscv/kernel/kernel_mode_vector.c diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h index 3e23e1786d05..10c796a792e7 100644 --- a/arch/riscv/include/asm/processor.h +++ b/arch/riscv/include/asm/processor.h @@ -72,6 +72,18 @@ struct task_struct; struct pt_regs; +/* + * We use a flag to track in-kernel Vector context. Currently the flag has the + * following meaning: + * + * - bit 0 indicates whether the in-kernel Vector context is active. The + * activation of this state disables the preemption. + */ + +#define RISCV_KERNEL_MODE_V_MASK 0x1 + +#define RISCV_KERNEL_MODE_V 0x1 + /* CPU-specific state of a task */ struct thread_struct { /* Callee-saved registers */ @@ -80,7 +92,8 @@ struct thread_struct { unsigned long s[12]; /* s[0]: frame pointer */ struct __riscv_d_ext_state fstate; unsigned long bad_cause; - unsigned long vstate_ctrl; + u32 riscv_v_flags; + u32 vstate_ctrl; struct __riscv_v_ext_state vstate; }; diff --git a/arch/riscv/include/asm/simd.h b/arch/riscv/include/asm/simd.h new file mode 100644 index 000000000000..269752bfa2cc --- /dev/null +++ b/arch/riscv/include/asm/simd.h @@ -0,0 +1,42 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2017 Linaro Ltd. + * Copyright (C) 2023 SiFive + */ + +#ifndef __ASM_SIMD_H +#define __ASM_SIMD_H + +#include +#include +#include +#include +#include + +#ifdef CONFIG_RISCV_ISA_V +/* + * may_use_simd - 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_simd(void) +{ + /* + * RISCV_KERNEL_MODE_V is only set while preemption is disabled, + * and is clear whenever preemption is enabled. + */ + return !in_hardirq() && !in_nmi() && !(riscv_v_ctx_cnt() & RISCV_KERNEL_MODE_V_MASK); +} + +#else /* ! CONFIG_RISCV_ISA_V */ + +static __must_check inline bool may_use_simd(void) +{ + return false; +} + +#endif /* ! CONFIG_RISCV_ISA_V */ + +#endif diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h index c5ee07b3df07..a2db3dbe97eb 100644 --- a/arch/riscv/include/asm/vector.h +++ b/arch/riscv/include/asm/vector.h @@ -22,6 +22,27 @@ extern unsigned long riscv_v_vsize; int riscv_v_setup_vsize(void); bool riscv_v_first_use_handler(struct pt_regs *regs); +void kernel_vector_begin(void); +void kernel_vector_end(void); +void get_cpu_vector_context(void); +void put_cpu_vector_context(void); + +static inline void riscv_v_ctx_cnt_add(u32 offset) +{ + current->thread.riscv_v_flags += offset; + barrier(); +} + +static inline void riscv_v_ctx_cnt_sub(u32 offset) +{ + barrier(); + current->thread.riscv_v_flags -= offset; +} + +static inline u32 riscv_v_ctx_cnt(void) +{ + return READ_ONCE(current->thread.riscv_v_flags); +} static __always_inline bool has_vector(void) { diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile index 95cf25d48405..0597bb668b6e 100644 --- a/arch/riscv/kernel/Makefile +++ b/arch/riscv/kernel/Makefile @@ -62,6 +62,7 @@ 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..c9ccf21dd16c --- /dev/null +++ b/arch/riscv/kernel/kernel_mode_vector.c @@ -0,0 +1,95 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2012 ARM Ltd. + * Author: Catalin Marinas + * Copyright (C) 2017 Linaro Ltd. + * Copyright (C) 2021 SiFive + */ +#include +#include +#include +#include +#include + +#include +#include +#include + +/* + * 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. + */ +void get_cpu_vector_context(void) +{ + preempt_disable(); + + WARN_ON(riscv_v_ctx_cnt() & RISCV_KERNEL_MODE_V_MASK); + riscv_v_ctx_cnt_add(RISCV_KERNEL_MODE_V); +} + +/* + * 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. + */ +void put_cpu_vector_context(void) +{ + WARN_ON(!(riscv_v_ctx_cnt() & RISCV_KERNEL_MODE_V_MASK)); + riscv_v_ctx_cnt_sub(RISCV_KERNEL_MODE_V); + + preempt_enable(); +} + +/* + * kernel_vector_begin(): obtain the CPU vector registers for use by the calling + * context + * + * Must not be called unless may_use_simd() returns true. + * Task context in the vector registers is saved back to memory as necessary. + * + * A matching call to kernel_vector_end() must be made before returning from the + * calling context. + * + * The caller may freely use the vector registers until kernel_vector_end() is + * called. + */ +void kernel_vector_begin(void) +{ + if (WARN_ON(!has_vector())) + return; + + BUG_ON(!may_use_simd()); + + get_cpu_vector_context(); + + riscv_v_vstate_save(current, task_pt_regs(current)); + + riscv_v_enable(); +} +EXPORT_SYMBOL_GPL(kernel_vector_begin); + +/* + * kernel_vector_end(): give the CPU vector registers back to the current task + * + * Must be called from a context in which kernel_vector_begin() was previously + * called, with no call to kernel_vector_end() in the meantime. + * + * The caller must not use the vector registers after this function is called, + * unless kernel_vector_begin() is called again in the meantime. + */ +void kernel_vector_end(void) +{ + if (WARN_ON(!has_vector())) + return; + + riscv_v_vstate_restore(current, task_pt_regs(current)); + + riscv_v_disable(); + + put_cpu_vector_context(); +} +EXPORT_SYMBOL_GPL(kernel_vector_end); diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index e32d737e039f..bb879ab38101 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -169,7 +169,6 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) *dst = *src; /* clear entire V context, including datap for a new task */ memset(&dst->thread.vstate, 0, sizeof(struct __riscv_v_ext_state)); - return 0; } @@ -203,6 +202,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) childregs->a0 = 0; /* Return value of fork() */ p->thread.s[0] = 0; } + p->thread.riscv_v_flags = 0; p->thread.ra = (unsigned long)ret_from_fork; p->thread.sp = (unsigned long)childregs; /* kernel sp */ return 0;