LXR linux/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
  18static 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
  26static 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 */
  43static 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 */
  60