1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __X86_KERNEL_FPU_CONTEXT_H
3 #define __X86_KERNEL_FPU_CONTEXT_H
4 
5 #include <asm/fpu/xstate.h>
6 #include <asm/trace/fpu.h>
7 
8 /* Functions related to FPU context tracking */
9 
10 /*
11  * The in-register FPU state for an FPU context on a CPU is assumed to be
12  * valid if the fpu->last_cpu matches the CPU, and the fpu_fpregs_owner_ctx
13  * matches the FPU.
14  *
15  * If the FPU register state is valid, the kernel can skip restoring the
16  * FPU state from memory.
17  *
18  * Any code that clobbers the FPU registers or updates the in-memory
19  * FPU state for a task MUST let the rest of the kernel know that the
20  * FPU registers are no longer valid for this task.
21  *
22  * Either one of these invalidation functions is enough. Invalidate
23  * a resource you control: CPU if using the CPU for something else
24  * (with preemption disabled), FPU for the current task, or a task that
25  * is prevented from running by the current task.
26  */
__cpu_invalidate_fpregs_state(void)27 static inline void __cpu_invalidate_fpregs_state(void)
28 {
29 	__this_cpu_write(fpu_fpregs_owner_ctx, NULL);
30 }
31 
__fpu_invalidate_fpregs_state(struct fpu * fpu)32 static inline void __fpu_invalidate_fpregs_state(struct fpu *fpu)
33 {
34 	fpu->last_cpu = -1;
35 }
36 
fpregs_state_valid(struct fpu * fpu,unsigned int cpu)37 static inline int fpregs_state_valid(struct fpu *fpu, unsigned int cpu)
38 {
39 	return fpu == this_cpu_read(fpu_fpregs_owner_ctx) && cpu == fpu->last_cpu;
40 }
41 
fpregs_deactivate(struct fpu * fpu)42 static inline void fpregs_deactivate(struct fpu *fpu)
43 {
44 	__this_cpu_write(fpu_fpregs_owner_ctx, NULL);
45 	trace_x86_fpu_regs_deactivated(fpu);
46 }
47 
fpregs_activate(struct fpu * fpu)48 static inline void fpregs_activate(struct fpu *fpu)
49 {
50 	__this_cpu_write(fpu_fpregs_owner_ctx, fpu);
51 	trace_x86_fpu_regs_activated(fpu);
52 }
53 
54 /* Internal helper for switch_fpu_return() and signal frame setup */
fpregs_restore_userregs(void)55 static inline void fpregs_restore_userregs(void)
56 {
57 	struct fpu *fpu = &current->thread.fpu;
58 	int cpu = smp_processor_id();
59 
60 	if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
61 		return;
62 
63 	if (!fpregs_state_valid(fpu, cpu)) {
64 		/*
65 		 * This restores _all_ xstate which has not been
66 		 * established yet.
67 		 *
68 		 * If PKRU is enabled, then the PKRU value is already
69 		 * correct because it was either set in switch_to() or in
70 		 * flush_thread(). So it is excluded because it might be
71 		 * not up to date in current->thread.fpu.xsave state.
72 		 *
73 		 * XFD state is handled in restore_fpregs_from_fpstate().
74 		 */
75 		restore_fpregs_from_fpstate(fpu->fpstate, XFEATURE_MASK_FPSTATE);
76 
77 		fpregs_activate(fpu);
78 		fpu->last_cpu = cpu;
79 	}
80 	clear_thread_flag(TIF_NEED_FPU_LOAD);
81 }
82 
83 #endif
84