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1 /*
2  * Copyright (C) 1994 Linus Torvalds
3  *
4  * Pentium III FXSR, SSE support
5  * General FPU state handling cleanups
6  *	Gareth Hughes <gareth@valinux.com>, May 2000
7  * x86-64 work by Andi Kleen 2002
8  */
9 
10 #ifndef _ASM_X86_I387_H
11 #define _ASM_X86_I387_H
12 
13 #ifndef __ASSEMBLY__
14 
15 #include <linux/sched.h>
16 #include <linux/hardirq.h>
17 
18 struct pt_regs;
19 struct user_i387_struct;
20 
21 extern int init_fpu(struct task_struct *child);
22 extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);
23 extern void math_state_restore(void);
24 
25 extern bool irq_fpu_usable(void);
26 extern void kernel_fpu_begin(void);
27 extern void kernel_fpu_end(void);
28 
29 /*
30  * Some instructions like VIA's padlock instructions generate a spurious
31  * DNA fault but don't modify SSE registers. And these instructions
32  * get used from interrupt context as well. To prevent these kernel instructions
33  * in interrupt context interacting wrongly with other user/kernel fpu usage, we
34  * should use them only in the context of irq_ts_save/restore()
35  */
irq_ts_save(void)36 static inline int irq_ts_save(void)
37 {
38 	/*
39 	 * If in process context and not atomic, we can take a spurious DNA fault.
40 	 * Otherwise, doing clts() in process context requires disabling preemption
41 	 * or some heavy lifting like kernel_fpu_begin()
42 	 */
43 	if (!in_atomic())
44 		return 0;
45 
46 	if (read_cr0() & X86_CR0_TS) {
47 		clts();
48 		return 1;
49 	}
50 
51 	return 0;
52 }
53 
irq_ts_restore(int TS_state)54 static inline void irq_ts_restore(int TS_state)
55 {
56 	if (TS_state)
57 		stts();
58 }
59 
60 /*
61  * The question "does this thread have fpu access?"
62  * is slightly racy, since preemption could come in
63  * and revoke it immediately after the test.
64  *
65  * However, even in that very unlikely scenario,
66  * we can just assume we have FPU access - typically
67  * to save the FP state - we'll just take a #NM
68  * fault and get the FPU access back.
69  */
user_has_fpu(void)70 static inline int user_has_fpu(void)
71 {
72 	return current->thread.fpu.has_fpu;
73 }
74 
75 extern void unlazy_fpu(struct task_struct *tsk);
76 
77 #endif /* __ASSEMBLY__ */
78 
79 #endif /* _ASM_X86_I387_H */
80