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 fpu *fpu); 14 extern int fpu_clone(struct task_struct *dst, unsigned long clone_flags); 15 extern void fpu_flush_thread(void); 16 17 /* 18 * FPU state switching for scheduling. 19 * 20 * This is a two-stage process: 21 * 22 * - switch_fpu_prepare() saves the old state. 23 * This is done within the context of the old process. 24 * 25 * - switch_fpu_finish() sets TIF_NEED_FPU_LOAD; the floating point state 26 * will get loaded on return to userspace, or when the kernel needs it. 27 * 28 * If TIF_NEED_FPU_LOAD is cleared then the CPU's FPU registers 29 * are saved in the current thread's FPU register state. 30 * 31 * If TIF_NEED_FPU_LOAD is set then CPU's FPU registers may not 32 * hold current()'s FPU registers. It is required to load the 33 * registers before returning to userland or using the content 34 * otherwise. 35 * 36 * The FPU context is only stored/restored for a user task and 37 * PF_KTHREAD is used to distinguish between kernel and user threads. 38 */ 39 static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu) 40 { 41 if (cpu_feature_enabled(X86_FEATURE_FPU) && 42 !(current->flags & PF_KTHREAD)) { 43 save_fpregs_to_fpstate(old_fpu); 44 /* 45 * The save operation preserved register state, so the 46 * fpu_fpregs_owner_ctx is still @old_fpu. Store the 47 * current CPU number in @old_fpu, so the next return 48 * to user space can avoid the FPU register restore 49 * when is returns on the same CPU and still owns the 50 * context. 51 */ 52 old_fpu->last_cpu = cpu; 53 54 trace_x86_fpu_regs_deactivated(old_fpu); 55 } 56 } 57 58 /* 59 * Delay loading of the complete FPU state until the return to userland. 60 * PKRU is handled separately. 61 */ 62 static inline void switch_fpu_finish(void) 63 { 64 if (cpu_feature_enabled(X86_FEATURE_FPU)) 65 set_thread_flag(TIF_NEED_FPU_LOAD); 66 } 67 68 #endif /* _ASM_X86_FPU_SCHED_H */ 69