diff --git a/OvmfPkg/XenBusDxe/Ia32/InterlockedCompareExchange16.S b/OvmfPkg/XenBusDxe/Ia32/InterlockedCompareExchange16.S
new file mode 100644
index 0000000000..5306448515
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/Ia32/InterlockedCompareExchange16.S
@@ -0,0 +1,15 @@
+# UINT16
+# EFIAPI
+# InternalSyncCompareExchange16 (
+# IN volatile UINT16 *Value,
+# IN UINT16 CompareValue,
+# IN UINT16 ExchangeValue
+# );
+ASM_GLOBAL ASM_PFX(InternalSyncCompareExchange16)
+ASM_PFX(InternalSyncCompareExchange16):
+ mov 4(%esp), %ecx
+ mov 8(%esp), %eax
+ mov 12(%esp), %edx
+ lock
+ cmpxchgw %dx, (%ecx)
+ ret
diff --git a/OvmfPkg/XenBusDxe/Ia32/InterlockedCompareExchange16.asm b/OvmfPkg/XenBusDxe/Ia32/InterlockedCompareExchange16.asm
new file mode 100644
index 0000000000..adcfbd080b
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/Ia32/InterlockedCompareExchange16.asm
@@ -0,0 +1,45 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2006, Intel Corporation. All rights reserved.
+; This program and the accompanying materials
+; are licensed and made available under the terms and conditions of the BSD License
+; which accompanies this distribution. The full text of the license may be found at
+; http://opensource.org/licenses/bsd-license.php.
+;
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;
+; Module Name:
+;
+; InterlockedCompareExchange16.Asm
+;
+; Abstract:
+;
+; InterlockedCompareExchange16 function
+;
+; Notes:
+;
+;------------------------------------------------------------------------------
+
+ .486
+ .model flat,C
+ .code
+
+;------------------------------------------------------------------------------
+; UINT32
+; EFIAPI
+; InternalSyncCompareExchange16 (
+; IN UINT16 *Value,
+; IN UINT16 CompareValue,
+; IN UINT16 ExchangeValue
+; );
+;------------------------------------------------------------------------------
+InternalSyncCompareExchange16 PROC
+ mov ecx, [esp + 4]
+ mov eax, [esp + 8]
+ mov edx, [esp + 12]
+ lock cmpxchg [ecx], dx
+ ret
+InternalSyncCompareExchange16 ENDP
+
+ END
diff --git a/OvmfPkg/XenBusDxe/InterlockedCompareExchange16.c b/OvmfPkg/XenBusDxe/InterlockedCompareExchange16.c
new file mode 100644
index 0000000000..2b0fadd88d
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/InterlockedCompareExchange16.c
@@ -0,0 +1,33 @@
+#include
+#include "InterlockedCompareExchange16.h"
+
+/**
+ Performs an atomic compare exchange operation on a 16-bit unsigned integer.
+
+ Performs an atomic compare exchange operation on the 16-bit unsigned integer
+ specified by Value. If Value is equal to CompareValue, then Value is set to
+ ExchangeValue and CompareValue is returned. If Value is not equal to CompareValue,
+ then Value is returned. The compare exchange operation must be performed using
+ MP safe mechanisms.
+
+ If Value is NULL, then ASSERT().
+
+ @param Value A pointer to the 16-bit value for the compare exchange
+ operation.
+ @param CompareValue 16-bit value used in compare operation.
+ @param ExchangeValue 16-bit value used in exchange operation.
+
+ @return The original *Value before exchange.
+
+**/
+UINT16
+EFIAPI
+InterlockedCompareExchange16 (
+ IN OUT UINT16 *Value,
+ IN UINT16 CompareValue,
+ IN UINT16 ExchangeValue
+ )
+{
+ ASSERT (Value != NULL);
+ return InternalSyncCompareExchange16 (Value, CompareValue, ExchangeValue);
+}
diff --git a/OvmfPkg/XenBusDxe/InterlockedCompareExchange16.h b/OvmfPkg/XenBusDxe/InterlockedCompareExchange16.h
new file mode 100644
index 0000000000..fd3f15b1c8
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/InterlockedCompareExchange16.h
@@ -0,0 +1,38 @@
+/**
+ Assembly implementation of InterlockedCompareExchange16.
+
+ Look at the documentation of InterlockedCompareExchange16.
+**/
+UINT16
+EFIAPI
+InternalSyncCompareExchange16 (
+ IN volatile UINT16 *Value,
+ IN UINT16 CompareValue,
+ IN UINT16 ExchangeValue
+ );
+
+/**
+ Performs an atomic compare exchange operation on a 16-bit unsigned integer.
+
+ Performs an atomic compare exchange operation on the 16-bit unsigned integer
+ specified by Value. If Value is equal to CompareValue, then Value is set to
+ ExchangeValue and CompareValue is returned. If Value is not equal to CompareValue,
+ then Value is returned. The compare exchange operation must be performed using
+ MP safe mechanisms.
+
+ If Value is NULL, then ASSERT().
+
+ @param Value A pointer to the 16-bit value for the compare exchange
+ operation.
+ @param CompareValue 16-bit value used in compare operation.
+ @param ExchangeValue 16-bit value used in exchange operation.
+
+ @return The original *Value before exchange.
+**/
+UINT16
+EFIAPI
+InterlockedCompareExchange16 (
+ IN OUT UINT16 *Value,
+ IN UINT16 CompareValue,
+ IN UINT16 ExchangeValue
+ );
diff --git a/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.S b/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.S
new file mode 100644
index 0000000000..23e08f3f6e
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.S
@@ -0,0 +1,13 @@
+# UINT16
+# EFIAPI
+# InternalSyncCompareExchange16 (
+# IN volatile UINT16 *Value,
+# IN UINT16 CompareValue,
+# IN UINT16 ExchangeValue
+# );
+ASM_GLOBAL ASM_PFX(InternalSyncCompareExchange16)
+ASM_PFX(InternalSyncCompareExchange16):
+ mov %edx, %eax
+ lock
+ cmpxchgw %r8w, (%rcx)
+ ret
diff --git a/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.asm b/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.asm
new file mode 100644
index 0000000000..b23e421abc
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/X64/InterlockedCompareExchange16.asm
@@ -0,0 +1,41 @@
+;------------------------------------------------------------------------------
+;
+; Copyright (c) 2006, Intel Corporation. All rights reserved.
+; This program and the accompanying materials
+; are licensed and made available under the terms and conditions of the BSD License
+; which accompanies this distribution. The full text of the license may be found at
+; http://opensource.org/licenses/bsd-license.php.
+;
+; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+;
+; Module Name:
+;
+; InterlockedCompareExchange16.Asm
+;
+; Abstract:
+;
+; InterlockedCompareExchange16 function
+;
+; Notes:
+;
+;------------------------------------------------------------------------------
+
+ .code
+
+;------------------------------------------------------------------------------
+; UINT16
+; EFIAPI
+; InterlockedCompareExchange16 (
+; IN UINT16 *Value,
+; IN UINT16 CompareValue,
+; IN UINT16 ExchangeValue
+; );
+;------------------------------------------------------------------------------
+InternalSyncCompareExchange16 PROC
+ mov eax, edx
+ lock cmpxchg [rcx], r8w
+ ret
+InternalSyncCompareExchange16 ENDP
+
+ END
diff --git a/OvmfPkg/XenBusDxe/XenBusDxe.inf b/OvmfPkg/XenBusDxe/XenBusDxe.inf
index add85213c6..4e92a204f2 100644
--- a/OvmfPkg/XenBusDxe/XenBusDxe.inf
+++ b/OvmfPkg/XenBusDxe/XenBusDxe.inf
@@ -36,14 +36,20 @@
ComponentName.h
XenHypercall.c
XenHypercall.h
+ InterlockedCompareExchange16.c
+ InterlockedCompareExchange16.h
[Sources.IA32]
Ia32/hypercall.S
Ia32/hypercall.asm
+ Ia32/InterlockedCompareExchange16.S
+ Ia32/InterlockedCompareExchange16.asm
[Sources.X64]
X64/hypercall.S
X64/hypercall.asm
+ X64/InterlockedCompareExchange16.S
+ X64/InterlockedCompareExchange16.asm
[LibraryClasses]
UefiDriverEntryPoint