Index: sys/amd64/include/cpufunc.h
===================================================================
--- sys/amd64/include/cpufunc.h
+++ sys/amd64/include/cpufunc.h
@@ -355,6 +355,20 @@
 	return (low | ((uint64_t)high << 32));
 }
 
+static __inline uint64_t
+rdtsc_ordered_lfence(void)
+{
+	lfence();
+	return (rdtsc());
+}
+
+static __inline uint64_t
+rdtsc_ordered_mfence(void)
+{
+	mfence();
+	return (rdtsc());
+}
+
 static __inline uint64_t
 rdtscp(void)
 {
@@ -1017,6 +1031,10 @@
 
 #endif	/* __GNUCLIKE_ASM && __CC_SUPPORTS___INLINE */
 
+#ifdef _KERNEL
+uint64_t rdtsc_ordered(void);
+#endif /* _KERNEL */
+
 void	reset_dbregs(void);
 
 #ifdef _KERNEL
Index: sys/conf/files.x86
===================================================================
--- sys/conf/files.x86
+++ sys/conf/files.x86
@@ -319,6 +319,7 @@
 x86/x86/mp_watchdog.c		optional	mp_watchdog smp
 x86/x86/nexus.c			standard
 x86/x86/pvclock.c		standard
+x86/x86/rdtsc_ordered.c		standard
 x86/x86/stack_machdep.c		optional	ddb | stack
 x86/x86/tsc.c			standard
 x86/x86/ucode.c			standard
Index: sys/i386/include/cpufunc.h
===================================================================
--- sys/i386/include/cpufunc.h
+++ sys/i386/include/cpufunc.h
@@ -394,6 +394,20 @@
 	return (rv);
 }
 
+static __inline uint64_t
+rdtsc_ordered_lfence(void)
+{
+	lfence();
+	return (rdtsc());
+}
+
+static __inline uint64_t
+rdtsc_ordered_mfence(void)
+{
+	mfence();
+	return (rdtsc());
+}
+
 static __inline uint64_t
 rdtscp(void)
 {
@@ -832,6 +846,10 @@
 
 #endif	/* __GNUCLIKE_ASM && __CC_SUPPORTS___INLINE */
 
+#ifdef _KERNEL
+uint64_t rdtsc_ordered(void);
+#endif /* _KERNEL */
+
 void    reset_dbregs(void);
 
 #ifdef _KERNEL
Index: sys/x86/x86/rdtsc_ordered.c
===================================================================
--- /dev/null
+++ sys/x86/x86/rdtsc_ordered.c
@@ -0,0 +1,54 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2021 Juniper Networks, Inc.
+ * Copyright (c) 2021 Klara, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <sys/pcpu.h>
+
+#include <machine/cpufunc.h>
+#include <machine/cputypes.h>
+#include <machine/md_var.h>
+#include <machine/specialreg.h>
+
+#include <x86/ifunc.h>
+
+DEFINE_IFUNC(, uint64_t, rdtsc_ordered, (void))
+{
+	bool cpu_is_amd = cpu_vendor_id == CPU_VENDOR_AMD ||
+	    cpu_vendor_id == CPU_VENDOR_HYGON;
+
+	if ((amd_feature & AMDID_RDTSCP) != 0)
+		return (rdtscp);
+	else if ((cpu_feature & CPUID_SSE2) != 0)
+		return (cpu_is_amd ? rdtsc_ordered_mfence :
+		    rdtsc_ordered_lfence);
+	else
+		return (rdtsc);
+}