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