diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index ea27a8dd189cbecfdd796046f51ef31da7f93c56..63f91679af733d7e86db34163ed95668d7bdd701 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -74,6 +74,12 @@ unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
 	u8 ret_flags;
 
 	version = src->version;
+	/* Note: emulated platforms which do not advertise SSE2 support
+	 * result in kvmclock not using the necessary RDTSC barriers.
+	 * Without barriers, it is possible that RDTSC instruction reads from
+	 * the time stamp counter outside rdtsc_barrier protected section
+	 * below, resulting in violation of monotonicity.
+	 */
 	rdtsc_barrier();
 	offset = pvclock_get_nsec_offset(src);
 	ret = src->system_time + offset;