1 files changed, 10 insertions, 5 deletions

diff --git a/include/asm-i386/tsc.h b/include/asm-i386/tsc.h
index 84016ff481b9..3f3c1fa000b4 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);