arch/x86/include/asm/mwait.h

   1 #ifndef _ASM_X86_MWAIT_H
   2 #define _ASM_X86_MWAIT_H
   3
   4 #include <linux/sched.h>
   5
   6 #define MWAIT_SUBSTATE_MASK             0xf
   7 #define MWAIT_CSTATE_MASK               0xf
   8 #define MWAIT_SUBSTATE_SIZE             4
   9 #define MWAIT_HINT2CSTATE(hint)         (((hint) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK)
  10 #define MWAIT_HINT2SUBSTATE(hint)       ((hint) & MWAIT_CSTATE_MASK)
  11
  12 #define CPUID_MWAIT_LEAF                5
  13 #define CPUID5_ECX_EXTENSIONS_SUPPORTED 0x1
  14 #define CPUID5_ECX_INTERRUPT_BREAK      0x2
  15
  16 #define MWAIT_ECX_INTERRUPT_BREAK       0x1
  17
  18 static inline void __monitor(const void *eax, unsigned long ecx,
  19                              unsigned long edx)
  20 {
  21         /* "monitor %eax, %ecx, %edx;" */
  22         asm volatile(".byte 0x0f, 0x01, 0xc8;"
  23                      :: "a" (eax), "c" (ecx), "d"(edx));
  24 }
  25
  26 static inline void __mwait(unsigned long eax, unsigned long ecx)
  27 {
  28         /* "mwait %eax, %ecx;" */
  29         asm volatile(".byte 0x0f, 0x01, 0xc9;"
  30                      :: "a" (eax), "c" (ecx));
  31 }
  32
  33 /*
  34  * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
  35  * which can obviate IPI to trigger checking of need_resched.
  36  * We execute MONITOR against need_resched and enter optimized wait state
  37  * through MWAIT. Whenever someone changes need_resched, we would be woken
  38  * up from MWAIT (without an IPI).
  39  *
  40  * New with Core Duo processors, MWAIT can take some hints based on CPU
  41  * capability.
  42  */
  43 static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx)
  44 {
  45         if (!current_set_polling_and_test()) {
  46                 if (static_cpu_has_bug(X86_BUG_CLFLUSH_MONITOR)) {
  47                         mb();
  48                         clflush((void *)&current_thread_info()->flags);
  49                         mb();
  50                 }
  51
  52                 __monitor((void *)&current_thread_info()->flags, 0, 0);
  53                 if (!need_resched())
  54                         __mwait(eax, ecx);
  55         }
  56         current_clr_polling();
  57 }
  58
  59 #endif /* _ASM_X86_MWAIT_H */