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authorGreentime Hu <greentime.hu@sifive.com>2024-01-15 05:59:20 +0000
committerPalmer Dabbelt <palmer@rivosinc.com>2024-01-16 07:13:53 -0800
commitecd2ada8a5e0b464dab54f71d4ba7bbf5708711f (patch)
tree23dd7e28a56871c4286f8dd07bb1bf5dbda14e18 /arch
parentb85ea95d086471afb4ad062012a4d73cd328fa86 (diff)
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riscv: Add support for kernel mode vector
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 <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: Andy Chiu <andy.chiu@sifive.com> Reviewed-by: Eric Biggers <ebiggers@google.com> Tested-by: Björn Töpel <bjorn@rivosinc.com> Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> Link: https://lore.kernel.org/r/20240115055929.4736-2-andy.chiu@sifive.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/riscv/include/asm/processor.h12
-rw-r--r--arch/riscv/include/asm/simd.h44
-rw-r--r--arch/riscv/include/asm/vector.h9
-rw-r--r--arch/riscv/kernel/Makefile1
-rw-r--r--arch/riscv/kernel/kernel_mode_vector.c116
-rw-r--r--arch/riscv/kernel/process.c1
6 files changed, 182 insertions, 1 deletions
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index f19f861cda54..4809f20a2053 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -73,6 +73,15 @@
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 0x1
+
/* CPU-specific state of a task */
struct thread_struct {
/* Callee-saved registers */
@@ -81,7 +90,8 @@ 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;
unsigned long align_ctl;
};
diff --git a/arch/riscv/include/asm/simd.h b/arch/riscv/include/asm/simd.h
new file mode 100644
index 000000000000..ef8af413a9fc
--- /dev/null
+++ b/arch/riscv/include/asm/simd.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
+ * Copyright (C) 2023 SiFive
+ */
+
+#ifndef __ASM_SIMD_H
+#define __ASM_SIMD_H
+
+#include <linux/compiler.h>
+#include <linux/irqflags.h>
+#include <linux/percpu.h>
+#include <linux/preempt.h>
+#include <linux/types.h>
+
+#include <asm/vector.h>
+
+#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_flags() & RISCV_KERNEL_MODE_V);
+}
+
+#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 87aaef656257..71af3404fda1 100644
--- a/arch/riscv/include/asm/vector.h
+++ b/arch/riscv/include/asm/vector.h
@@ -22,6 +22,15 @@
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 u32 riscv_v_flags(void)
+{
+ return 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 fee22a3d1b53..8c58595696b3 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -63,6 +63,7 @@ obj-$(CONFIG_MMU) += vdso.o vdso/
obj-$(CONFIG_RISCV_MISALIGNED) += 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..114cf4f0a0eb
--- /dev/null
+++ b/arch/riscv/kernel/kernel_mode_vector.c
@@ -0,0 +1,116 @@
+// 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>
+#include <asm/simd.h>
+
+static inline void riscv_v_flags_set(u32 flags)
+{
+ current->thread.riscv_v_flags = flags;
+}
+
+static inline void riscv_v_start(u32 flags)
+{
+ int orig;
+
+ orig = riscv_v_flags();
+ BUG_ON((orig & flags) != 0);
+ riscv_v_flags_set(orig | flags);
+}
+
+static inline void riscv_v_stop(u32 flags)
+{
+ int orig;
+
+ orig = riscv_v_flags();
+ BUG_ON((orig & flags) == 0);
+ riscv_v_flags_set(orig & ~flags);
+}
+
+/*
+ * 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();
+
+ riscv_v_start(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)
+{
+ riscv_v_stop(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 4f21d970a129..4a1275db1146 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -221,6 +221,7 @@ 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;