diff --git a/OvmfPkg/Library/QemuFwCfgS3Lib/PeiQemuFwCfgS3LibFwCfg.inf b/OvmfPkg/Library/QemuFwCfgS3Lib/PeiQemuFwCfgS3LibFwCfg.inf
index 2593af8e5b..890862076e 100644
--- a/OvmfPkg/Library/QemuFwCfgS3Lib/PeiQemuFwCfgS3LibFwCfg.inf
+++ b/OvmfPkg/Library/QemuFwCfgS3Lib/PeiQemuFwCfgS3LibFwCfg.inf
@@ -31,6 +31,8 @@
 #
 
 [Sources]
+  QemuFwCfgS3BasePei.c
+  QemuFwCfgS3Pei.c
   QemuFwCfgS3PeiDxe.c
 
 [Packages]
@@ -38,4 +40,5 @@
   OvmfPkg/OvmfPkg.dec
 
 [LibraryClasses]
+  DebugLib
   QemuFwCfgLib
diff --git a/OvmfPkg/Library/QemuFwCfgS3Lib/QemuFwCfgS3Pei.c b/OvmfPkg/Library/QemuFwCfgS3Lib/QemuFwCfgS3Pei.c
new file mode 100644
index 0000000000..d447e36fc0
--- /dev/null
+++ b/OvmfPkg/Library/QemuFwCfgS3Lib/QemuFwCfgS3Pei.c
@@ -0,0 +1,86 @@
+/** @file
+  Limited functionality QemuFwCfgS3Lib instance, for PEI phase modules.
+
+  QemuFwCfgS3Enabled() queries S3 enablement via fw_cfg. Other library APIs
+  will report lack of support.
+
+  Copyright (C) 2017, Red Hat, Inc.
+
+  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.
+**/
+
+#include <Library/QemuFwCfgS3Lib.h>
+
+/**
+  Install the client module's FW_CFG_BOOT_SCRIPT_CALLBACK_FUNCTION callback for
+  when the production of ACPI S3 Boot Script opcodes becomes possible.
+
+  Take ownership of the client-provided Context, and pass it to the callback
+  function, when the latter is invoked.
+
+  Allocate scratch space for those ACPI S3 Boot Script opcodes to work upon
+  that the client will produce in the callback function.
+
+  @param[in] Callback           FW_CFG_BOOT_SCRIPT_CALLBACK_FUNCTION to invoke
+                                when the production of ACPI S3 Boot Script
+                                opcodes becomes possible. Callback() may be
+                                called immediately from
+                                QemuFwCfgS3CallWhenBootScriptReady().
+
+  @param[in,out] Context        Client-provided data structure for the
+                                Callback() callback function to consume.
+
+                                If Context points to dynamically allocated
+                                memory, then Callback() must release it.
+
+                                If Context points to dynamically allocated
+                                memory, and
+                                QemuFwCfgS3CallWhenBootScriptReady() returns
+                                successfully, then the caller of
+                                QemuFwCfgS3CallWhenBootScriptReady() must
+                                neither dereference nor even evaluate Context
+                                any longer, as ownership of the referenced area
+                                has been transferred to Callback().
+
+  @param[in] ScratchBufferSize  The size of the scratch buffer that will hold,
+                                in reserved memory, all client data read,
+                                written, and checked by the ACPI S3 Boot Script
+                                opcodes produced by Callback().
+
+  @retval RETURN_UNSUPPORTED       The library instance does not support this
+                                   function.
+
+  @retval RETURN_NOT_FOUND         The fw_cfg DMA interface to QEMU is
+                                   unavailable.
+
+  @retval RETURN_BAD_BUFFER_SIZE   ScratchBufferSize is too large.
+
+  @retval RETURN_OUT_OF_RESOURCES  Memory allocation failed.
+
+  @retval RETURN_SUCCESS           Callback() has been installed, and the
+                                   ownership of Context has been transferred.
+                                   Reserved memory has been allocated for the
+                                   scratch buffer.
+
+                                   A successful invocation of
+                                   QemuFwCfgS3CallWhenBootScriptReady() cannot
+                                   be rolled back.
+
+  @return                          Error codes from underlying functions.
+**/
+EFIAPI
+RETURN_STATUS
+QemuFwCfgS3CallWhenBootScriptReady (
+  IN     FW_CFG_BOOT_SCRIPT_CALLBACK_FUNCTION *Callback,
+  IN OUT VOID                                 *Context,          OPTIONAL
+  IN     UINTN                                ScratchBufferSize
+  )
+{
+  return RETURN_UNSUPPORTED;
+}