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 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  */
  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
  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  */
  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 */