1 files changed, 83 insertions, 0 deletions
diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
new file mode 100644
index 000000000..11463489f
--- /dev/null
+++ b/arch/riscv/include/asm/switch_to.h
@@ -0,0 +1,83 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ */
+
+#ifndef _ASM_RISCV_SWITCH_TO_H
+#define _ASM_RISCV_SWITCH_TO_H
+
+#include <linux/jump_label.h>
+#include <linux/sched/task_stack.h>
+#include <asm/hwcap.h>
+#include <asm/processor.h>
+#include <asm/ptrace.h>
+#include <asm/csr.h>
+
+#ifdef CONFIG_FPU
+extern void __fstate_save(struct task_struct *save_to);
+extern void __fstate_restore(struct task_struct *restore_from);
+
+static inline void __fstate_clean(struct pt_regs *regs)
+{
+	regs->status = (regs->status & ~SR_FS) | SR_FS_CLEAN;
+}
+
+static inline void fstate_off(struct task_struct *task,
+			      struct pt_regs *regs)
+{
+	regs->status = (regs->status & ~SR_FS) | SR_FS_OFF;
+}
+
+static inline void fstate_save(struct task_struct *task,
+			       struct pt_regs *regs)
+{
+	if ((regs->status & SR_FS) == SR_FS_DIRTY) {
+		__fstate_save(task);
+		__fstate_clean(regs);
+	}
+}
+
+static inline void fstate_restore(struct task_struct *task,
+				  struct pt_regs *regs)
+{
+	if ((regs->status & SR_FS) != SR_FS_OFF) {
+		__fstate_restore(task);
+		__fstate_clean(regs);
+	}
+}
+
+static inline void __switch_to_aux(struct task_struct *prev,
+				   struct task_struct *next)
+{
+	struct pt_regs *regs;
+
+	regs = task_pt_regs(prev);
+	if (unlikely(regs->status & SR_SD))
+		fstate_save(prev, regs);
+	fstate_restore(next, task_pt_regs(next));
+}
+
+static __always_inline bool has_fpu(void)
+{
+	return static_branch_likely(&riscv_isa_ext_keys[RISCV_ISA_EXT_KEY_FPU]);
+}
+#else
+static __always_inline bool has_fpu(void) { return false; }
+#define fstate_save(task, regs) do { } while (0)
+#define fstate_restore(task, regs) do { } while (0)
+#define __switch_to_aux(__prev, __next) do { } while (0)
+#endif
+
+extern struct task_struct *__switch_to(struct task_struct *,
+				       struct task_struct *);
+
+#define switch_to(prev, next, last)			\
+do {							\
+	struct task_struct *__prev = (prev);		\
+	struct task_struct *__next = (next);		\
+	if (has_fpu())					\
+		__switch_to_aux(__prev, __next);	\
+	((last) = __switch_to(__prev, __next));		\
+} while (0)
+
+#endif /* _ASM_RISCV_SWITCH_TO_H */