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 fpstate_alloc_init(struct task_struct *curr);
  22 extern void fpstate_init(struct fpu *fpu);
  23 extern void fpu__flush_thread(struct task_struct *tsk);
  24
  25 extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);
  26 extern void fpu__restore(void);
  27 extern void fpu__init_check_bugs(void);
  28
  29 extern bool irq_fpu_usable(void);
  30
  31 /*
  32  * Careful: __kernel_fpu_begin/end() must be called with preempt disabled
  33  * and they don't touch the preempt state on their own.
  34  * If you enable preemption after __kernel_fpu_begin(), preempt notifier
  35  * should call the __kernel_fpu_end() to prevent the kernel/user FPU
  36  * state from getting corrupted. KVM for example uses this model.
  37  *
  38  * All other cases use kernel_fpu_begin/end() which disable preemption
  39  * during kernel FPU usage.
  40  */
  41 extern void __kernel_fpu_begin(void);
  42 extern void __kernel_fpu_end(void);
  43
  44 static inline void kernel_fpu_begin(void)
  45 {
  46         preempt_disable();
  47         WARN_ON_ONCE(!irq_fpu_usable());
  48         __kernel_fpu_begin();
  49 }
  50
  51 static inline void kernel_fpu_end(void)
  52 {
  53         __kernel_fpu_end();
  54         preempt_enable();
  55 }
  56
  57 /* Must be called with preempt disabled */
  58 extern void kernel_fpu_disable(void);
  59 extern void kernel_fpu_enable(void);
  60
  61 /*
  62  * Some instructions like VIA's padlock instructions generate a spurious
  63  * DNA fault but don't modify SSE registers. And these instructions
  64  * get used from interrupt context as well. To prevent these kernel instructions
  65  * in interrupt context interacting wrongly with other user/kernel fpu usage, we
  66  * should use them only in the context of irq_ts_save/restore()
  67  */
  68 static inline int irq_ts_save(void)
  69 {
  70         /*
  71          * If in process context and not atomic, we can take a spurious DNA fault.
  72          * Otherwise, doing clts() in process context requires disabling preemption
  73          * or some heavy lifting like kernel_fpu_begin()
  74          */
  75         if (!in_atomic())
  76                 return 0;
  77
  78         if (read_cr0() & X86_CR0_TS) {
  79                 clts();
  80                 return 1;
  81         }
  82
  83         return 0;
  84 }
  85
  86 static inline void irq_ts_restore(int TS_state)
  87 {
  88         if (TS_state)
  89                 stts();
  90 }
  91
  92 /*
  93  * The question "does this thread have fpu access?"
  94  * is slightly racy, since preemption could come in
  95  * and revoke it immediately after the test.
  96  *
  97  * However, even in that very unlikely scenario,
  98  * we can just assume we have FPU access - typically
  99  * to save the FP state - we'll just take a #NM
 100  * fault and get the FPU access back.
 101  */
 102 static inline int user_has_fpu(void)
 103 {
 104         return current->thread.fpu.has_fpu;
 105 }
 106
 107 extern void fpu__save(struct task_struct *tsk);
 108
 109 #endif /* __ASSEMBLY__ */
 110
 111 #endif /* _ASM_X86_I387_H */