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, unsigned long 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(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(old); 38 39 set_tsk_thread_flag(old, TIF_NEED_FPU_LOAD); 40 save_fpregs_to_fpstate(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(old_fpu); 52 } 53 } 54 55 #endif /* _ASM_X86_FPU_SCHED_H */ 56