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 void fpu_finit(struct fpu *fpu);
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
28 /*
29 * Careful: __kernel_fpu_begin/end() must be called with preempt disabled
30 * and they don't touch the preempt state on their own.
31 * If you enable preemption after __kernel_fpu_begin(), preempt notifier
32 * should call the __kernel_fpu_end() to prevent the kernel/user FPU
33 * state from getting corrupted. KVM for example uses this model.
34 *
35 * All other cases use kernel_fpu_begin/end() which disable preemption
36 * during kernel FPU usage.
37 */
38 extern void __kernel_fpu_begin(void);
39 extern void __kernel_fpu_end(void);
40
kernel_fpu_begin(void)41 static inline void kernel_fpu_begin(void)
42 {
43 WARN_ON_ONCE(!irq_fpu_usable());
44 preempt_disable();
45 __kernel_fpu_begin();
46 }
47
kernel_fpu_end(void)48 static inline void kernel_fpu_end(void)
49 {
50 __kernel_fpu_end();
51 preempt_enable();
52 }
53
54 /*
55 * Some instructions like VIA's padlock instructions generate a spurious
56 * DNA fault but don't modify SSE registers. And these instructions
57 * get used from interrupt context as well. To prevent these kernel instructions
58 * in interrupt context interacting wrongly with other user/kernel fpu usage, we
59 * should use them only in the context of irq_ts_save/restore()
60 */
irq_ts_save(void)61 static inline int irq_ts_save(void)
62 {
63 /*
64 * If in process context and not atomic, we can take a spurious DNA fault.
65 * Otherwise, doing clts() in process context requires disabling preemption
66 * or some heavy lifting like kernel_fpu_begin()
67 */
68 if (!in_atomic())
69 return 0;
70
71 if (read_cr0() & X86_CR0_TS) {
72 clts();
73 return 1;
74 }
75
76 return 0;
77 }
78
irq_ts_restore(int TS_state)79 static inline void irq_ts_restore(int TS_state)
80 {
81 if (TS_state)
82 stts();
83 }
84
85 /*
86 * The question "does this thread have fpu access?"
87 * is slightly racy, since preemption could come in
88 * and revoke it immediately after the test.
89 *
90 * However, even in that very unlikely scenario,
91 * we can just assume we have FPU access - typically
92 * to save the FP state - we'll just take a #NM
93 * fault and get the FPU access back.
94 */
user_has_fpu(void)95 static inline int user_has_fpu(void)
96 {
97 return current->thread.fpu.has_fpu;
98 }
99
100 extern void unlazy_fpu(struct task_struct *tsk);
101
102 #endif /* __ASSEMBLY__ */
103
104 #endif /* _ASM_X86_I387_H */
105