diff options
Diffstat (limited to 'include/asm-i386/tsc.h')
| -rw-r--r-- | include/asm-i386/tsc.h | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/include/asm-i386/tsc.h b/include/asm-i386/tsc.h index 84016ff481b9..62c091ffcccc 100644 --- a/include/asm-i386/tsc.h +++ b/include/asm-i386/tsc.h @@ -35,8 +35,18 @@ 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; + unsigned eax, edx; + + /* + * 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, + ASM_OUTPUT2("=a" (eax), "=d" (edx)), + "a" (0U), "d" (0U) : "ecx", "memory"); + ret = (((unsigned long long)edx) << 32) | ((unsigned long long)eax); + if (ret) + return ret; /* * Don't do an additional sync on CPUs where we know @@ -44,16 +54,13 @@ static __always_inline cycles_t get_cycles_sync(void) */ 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); |