+ 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;