diff options
Diffstat (limited to 'include/asm-i386/tsc.h')
| -rw-r--r-- | include/asm-i386/tsc.h | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/include/asm-i386/tsc.h b/include/asm-i386/tsc.h index 84016ff481b..3f3c1fa000b 100644 --- a/include/asm-i386/tsc.h +++ b/include/asm-i386/tsc.h @@ -35,25 +35,30 @@ static inline cycles_t get_cycles(void) 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); |