From 84f140bf86ec6b944a7a3955def554142af5faeb Mon Sep 17 00:00:00 2001
From: Kun Qin <kuqin@microsoft.com>
Date: Wed, 23 Apr 2025 11:27:39 -0700
Subject: [PATCH] OvmfPkg: StandaloneMmCpuFeaturesLib: Introduce
 SmmCpuFeaturesLib for Ovmf

This change adds the implementation of SmmCpuFeaturesLib for Ovmf to
operate with Standalone MM supported platforms.

Signed-off-by: Kun Qin <kun.qin@microsoft.com>
---
 .../StandaloneMmCpuFeaturesLib.c              | 75 +++++++++++++++++++
 .../StandaloneMmCpuFeaturesLib.inf            | 42 +++++++++++
 OvmfPkg/OvmfPkg.ci.yaml                       |  3 +-
 3 files changed, 119 insertions(+), 1 deletion(-)
 create mode 100644 OvmfPkg/Library/SmmCpuFeaturesLib/StandaloneMmCpuFeaturesLib.c
 create mode 100644 OvmfPkg/Library/SmmCpuFeaturesLib/StandaloneMmCpuFeaturesLib.inf

diff --git a/OvmfPkg/Library/SmmCpuFeaturesLib/StandaloneMmCpuFeaturesLib.c b/OvmfPkg/Library/SmmCpuFeaturesLib/StandaloneMmCpuFeaturesLib.c
new file mode 100644
index 0000000000..9f3b54ccda
--- /dev/null
+++ b/OvmfPkg/Library/SmmCpuFeaturesLib/StandaloneMmCpuFeaturesLib.c
@@ -0,0 +1,75 @@
+/** @file
+  The CPU specific programming for Standalone MM environment.
+
+  Copyright (c) 2010 - 2015, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) Microsoft Corporation.
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#include <PiMm.h>
+#include <Library/SmmCpuFeaturesLib.h>
+#include <Library/MmServicesTableLib.h>
+
+/**
+  The common constructor function
+
+  @retval EFI_SUCCESS      The constructor always returns EFI_SUCCESS.
+
+**/
+EFI_STATUS
+EFIAPI
+MmCpuFeaturesLibConstructorCommon (
+  VOID
+  );
+
+/**
+  Hook point in normal execution mode that allows the one CPU that was elected
+  as monarch during System Management Mode initialization to perform additional
+  initialization actions immediately after all of the CPUs have processed their
+  first SMI and called SmmCpuFeaturesInitializeProcessor() relocating SMBASE
+  into a buffer in SMRAM and called SmmCpuFeaturesHookReturnFromSmm().
+**/
+VOID
+EFIAPI
+SmmCpuFeaturesSmmRelocationComplete (
+  VOID
+  )
+{
+  // Do nothing for Standalone MM instance.
+}
+
+/**
+  Processor specific hook point each time a CPU exits System Management Mode.
+
+  @param[in] CpuIndex  The index of the CPU that is exiting SMM.  The value
+                       must be between 0 and the NumberOfCpus field in the
+                       System Management System Table (SMST).
+**/
+VOID
+EFIAPI
+SmmCpuFeaturesRendezvousExit (
+  IN UINTN  CpuIndex
+  )
+{
+  // Do nothing for Standalone MM instance.
+}
+
+/**
+  The constructor function
+
+  @param[in]  ImageHandle  The firmware allocated handle for the EFI image.
+  @param[in]  SystemTable  A pointer to the EFI System Table.
+
+  @retval EFI_SUCCESS      The constructor always returns EFI_SUCCESS.
+
+**/
+EFI_STATUS
+EFIAPI
+StandalonMmCpuFeaturesLibConstructor (
+  IN EFI_HANDLE           ImageHandle,
+  IN EFI_MM_SYSTEM_TABLE  *SystemTable
+  )
+{
+  return MmCpuFeaturesLibConstructorCommon ();
+}
diff --git a/OvmfPkg/Library/SmmCpuFeaturesLib/StandaloneMmCpuFeaturesLib.inf b/OvmfPkg/Library/SmmCpuFeaturesLib/StandaloneMmCpuFeaturesLib.inf
new file mode 100644
index 0000000000..ae7396a49c
--- /dev/null
+++ b/OvmfPkg/Library/SmmCpuFeaturesLib/StandaloneMmCpuFeaturesLib.inf
@@ -0,0 +1,42 @@
+## @file
+#  The CPU specific programming for Standalone MM environment.
+#
+#  Copyright (c) 2009 - 2015, Intel Corporation. All rights reserved.<BR>
+#  Copyright (c) Microsoft Corporation.
+#
+#  SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010005
+  BASE_NAME                      = StandaloneMmCpuFeaturesLib
+  MODULE_UNI_FILE                = StandaloneMmCpuFeaturesLib.uni
+  FILE_GUID                      = 74B868F6-7DC6-4CDE-86B1-27E9A7CEBFCC
+  MODULE_TYPE                    = MM_STANDALONE
+  VERSION_STRING                 = 1.0
+  PI_SPECIFICATION_VERSION       = 0x00010032
+  LIBRARY_CLASS                  = SmmCpuFeaturesLib
+  CONSTRUCTOR                    = StandalonMmCpuFeaturesLibConstructor
+
+[Sources]
+  SmmCpuFeaturesLib.c
+  StandaloneMmCpuFeaturesLib.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  OvmfPkg/OvmfPkg.dec
+  UefiCpuPkg/UefiCpuPkg.dec
+
+[LibraryClasses]
+  BaseLib
+  BaseMemoryLib
+  DebugLib
+  MemEncryptSevLib
+  PcdLib
+
+[Guids]
+  gSmmBaseHobGuid                ## CONSUMES
+
+[Pcd]
+  gUefiOvmfPkgTokenSpaceGuid.PcdQ35SmramAtDefaultSmbase
diff --git a/OvmfPkg/OvmfPkg.ci.yaml b/OvmfPkg/OvmfPkg.ci.yaml
index e4b729b4a8..62f3aef3c5 100644
--- a/OvmfPkg/OvmfPkg.ci.yaml
+++ b/OvmfPkg/OvmfPkg.ci.yaml
@@ -53,7 +53,8 @@
             "UefiCpuPkg/UefiCpuPkg.dec",
             "ShellPkg/ShellPkg.dec",
             "EmbeddedPkg/EmbeddedPkg.dec",
-            "SourceLevelDebugPkg/SourceLevelDebugPkg.dec"
+            "SourceLevelDebugPkg/SourceLevelDebugPkg.dec",
+            "StandaloneMmPkg/StandaloneMmPkg.dec"
         ],
         # For host based unit tests
         "AcceptableDependencies-HOST_APPLICATION":[