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Donenfeld" , Samuel Neves Cc: Heiko Stuebner , Herbert Xu , "David S. Miller" , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, Vincent Chen Subject: [RFC PATCH 2/6] riscv: Add support for kernel mode vector Date: Tue, 12 Sep 2023 13:57:24 +0200 Message-Id: <20230912115728.172982-3-bjorn@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230912115728.172982-1-bjorn@kernel.org> References: <20230912115728.172982-1-bjorn@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.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 --- arch/riscv/include/asm/simd.h | 50 ++++++++++++ arch/riscv/include/asm/vector.h | 2 + arch/riscv/kernel/Makefile | 1 + arch/riscv/kernel/kernel_mode_vector.c | 101 +++++++++++++++++++++++++ 4 files changed, 154 insertions(+) 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/simd.h b/arch/riscv/include/asm/simd.h new file mode 100644 index 000000000000..ef70af78005d --- /dev/null +++ b/arch/riscv/include/asm/simd.h @@ -0,0 +1,50 @@ +/* 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 + +DECLARE_PER_CPU(bool, vector_context_busy); + +/* + * 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) +{ + /* + * 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); +} + +#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 531873986a15..768acd517414 100644 --- a/arch/riscv/include/asm/vector.h +++ b/arch/riscv/include/asm/vector.h @@ -22,6 +22,8 @@ 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); 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..1c3b32d2b340 --- /dev/null +++ b/arch/riscv/kernel/kernel_mode_vector.c @@ -0,0 +1,101 @@ +// 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 + +DEFINE_PER_CPU(bool, 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_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()); + + riscv_v_vstate_save(current, task_pt_regs(current)); + + get_cpu_vector_context(); + + riscv_v_enable(); + + return 0; +} +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_set_restore(current, task_pt_regs(current)); + + riscv_v_disable(); + + put_cpu_vector_context(); +} +EXPORT_SYMBOL_GPL(kernel_vector_end);