| 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
|---|---|
| 2 | #ifndef _ASM_X86_FPU_SCHED_H |
| 3 | #define _ASM_X86_FPU_SCHED_H |
| 4 | |
| 5 | #include <linux/sched.h> |
| 6 | |
| 7 | #include <asm/cpufeature.h> |
| 8 | #include <asm/fpu/types.h> |
| 9 | |
| 10 | #include <asm/trace/fpu.h> |
| 11 | |
| 12 | extern void save_fpregs_to_fpstate(struct fpu *fpu); |
| 13 | extern void fpu__drop(struct task_struct *tsk); |
| 14 | extern int fpu_clone(struct task_struct *dst, u64 clone_flags, bool minimal, |
| 15 | unsigned long shstk_addr); |
| 16 | extern void fpu_flush_thread(void); |
| 17 | |
| 18 | /* |
| 19 | * FPU state switching for scheduling. |
| 20 | * |
| 21 | * switch_fpu() saves the old state and sets TIF_NEED_FPU_LOAD if |
| 22 | * TIF_NEED_FPU_LOAD is not set. This is done within the context |
| 23 | * of the old process. |
| 24 | * |
| 25 | * Once TIF_NEED_FPU_LOAD is set, it is required to load the |
| 26 | * registers before returning to userland or using the content |
| 27 | * otherwise. |
| 28 | * |
| 29 | * The FPU context is only stored/restored for a user task and |
| 30 | * PF_KTHREAD is used to distinguish between kernel and user threads. |
| 31 | */ |
| 32 | static inline void switch_fpu(struct task_struct *old, int cpu) |
| 33 | { |
| 34 | if (!test_tsk_thread_flag(tsk: old, TIF_NEED_FPU_LOAD) && |
| 35 | cpu_feature_enabled(X86_FEATURE_FPU) && |
| 36 | !(old->flags & (PF_KTHREAD | PF_USER_WORKER))) { |
| 37 | struct fpu *old_fpu = x86_task_fpu(task: old); |
| 38 | |
| 39 | set_tsk_thread_flag(tsk: old, TIF_NEED_FPU_LOAD); |
| 40 | save_fpregs_to_fpstate(fpu: old_fpu); |
| 41 | /* |
| 42 | * The save operation preserved register state, so the |
| 43 | * fpu_fpregs_owner_ctx is still @old_fpu. Store the |
| 44 | * current CPU number in @old_fpu, so the next return |
| 45 | * to user space can avoid the FPU register restore |
| 46 | * when is returns on the same CPU and still owns the |
| 47 | * context. See fpregs_restore_userregs(). |
| 48 | */ |
| 49 | old_fpu->last_cpu = cpu; |
| 50 | |
| 51 | trace_x86_fpu_regs_deactivated(fpu: old_fpu); |
| 52 | } |
| 53 | } |
| 54 | |
| 55 | #endif /* _ASM_X86_FPU_SCHED_H */ |
| 56 |