arch/x86/include/asm/i387.h

   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
  41 static inline void kernel_fpu_begin(void)
  42 {
  43         preempt_disable();
  44         WARN_ON_ONCE(!irq_fpu_usable());
  45         __kernel_fpu_begin();
  46 }
  47
  48 static inline void kernel_fpu_end(void)
  49 {
  50         __kernel_fpu_end();
  51         preempt_enable();
  52 }
  53
  54 /* Must be called with preempt disabled */
  55 extern void kernel_fpu_disable(void);
  56 extern void kernel_fpu_enable(void);
  57
  58 /*
  59  * Some instructions like VIA's padlock instructions generate a spurious
  60  * DNA fault but don't modify SSE registers. And these instructions
  61  * get used from interrupt context as well. To prevent these kernel instructions
  62  * in interrupt context interacting wrongly with other user/kernel fpu usage, we
  63  * should use them only in the context of irq_ts_save/restore()
  64  */
  65 static inline int irq_ts_save(void)
  66 {
  67         /*
  68          * If in process context and not atomic, we can take a spurious DNA fault.
  69          * Otherwise, doing clts() in process context requires disabling preemption
  70          * or some heavy lifting like kernel_fpu_begin()
  71          */
  72         if (!in_atomic())
  73                 return 0;
  74
  75         if (read_cr0() & X86_CR0_TS) {
  76                 clts();
  77                 return 1;
  78         }
  79
  80         return 0;
  81 }
  82
  83 static inline void irq_ts_restore(int TS_state)
  84 {
  85         if (TS_state)
  86                 stts();
  87 }
  88
  89 /*
  90  * The question "does this thread have fpu access?"
  91  * is slightly racy, since preemption could come in
  92  * and revoke it immediately after the test.
  93  *
  94  * However, even in that very unlikely scenario,
  95  * we can just assume we have FPU access - typically
  96  * to save the FP state - we'll just take a #NM
  97  * fault and get the FPU access back.
  98  */
  99 static inline int user_has_fpu(void)
 100 {
 101         return current->thread.fpu.has_fpu;
 102 }
 103
 104 extern void unlazy_fpu(struct task_struct *tsk);
 105
 106 #endif /* __ASSEMBLY__ */
 107
 108 #endif /* _ASM_X86_I387_H */