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20 * FPU registers are no longer valid for this task.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 */
27static inline void __cpu_invalidate_fpregs_state(void)
28{
29	__this_cpu_write(fpu_fpregs_owner_ctx, NULL);
30}
31
32static inline void __fpu_invalidate_fpregs_state(struct fpu *fpu)
33{
34	fpu->last_cpu = -1;
35}
36
37static 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
42static 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
48static 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 */
55static 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