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 *)¤t_thread_info()->flags); 49 mb(); 50 } 51 52 __monitor((void *)¤t_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