static __always_inline cycles_t get_cycles_sync(void)
{
unsigned long long ret;
-#ifdef X86_FEATURE_SYNC_RDTSC
unsigned eax;
+ /*
+ * Use RDTSCP if possible; it is guaranteed to be synchronous
+ * and doesn't cause a VMEXIT on Hypervisors
+ */
+ alternative_io(ASM_NOP3, ".byte 0x0f,0x01,0xf9", X86_FEATURE_RDTSCP,
+ "=A" (ret), "0" (0ULL) : "ecx", "memory");
+ if (ret)
+ return ret;
+
/*
* Don't do an additional sync on CPUs where we know
* RDTSC is already synchronous:
*/
alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC,
"=a" (eax), "0" (1) : "ebx","ecx","edx","memory");
-#else
- sync_core();
-#endif
rdtscll(ret);
return ret;
}
extern void tsc_init(void);
-extern void mark_tsc_unstable(void);
+extern void mark_tsc_unstable(char *reason);
extern int unsynchronized_tsc(void);
extern void init_tsc_clocksource(void);