Support Standalone MM in ConfigKnobShimLib and Autogen (#183)

# Preface

Please ensure you have read the [contribution
docs](https://github.com/microsoft/mu/blob/master/CONTRIBUTING.md) prior
to submitting the pull request. In particular,
[pull request
guidelines](https://github.com/microsoft/mu/blob/master/CONTRIBUTING.md#pull-request-best-practices).

## Description

Add Standalone MM support to ConfigKnobShimLib and the autogenerated
headers so that standalone MM modules can use the configuration
interfaces provided by mu_feature_config.

This switches to using PolicyLib as the interface to policy code in the
autogenerated header and adds a standalone MM appropriate get variable
interface to ConfigKnobShimLib.

For each item, place an "x" in between `[` and `]` if true. Example:
`[x]`.
_(you can also check items in the GitHub UI)_

- [x] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [ ] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
    in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
    a function in a new library class in a pre-existing module, ...
- [x] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [x] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
    outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
    on an a separate Web page, ...

## How This Was Tested

Tested on a physical platform with standalone MM config knobs enabled.

## Integration Instructions

Follow the integration instructions inthe docs section of this
repository, ensuring there is a separate config XML for standalone MM.

SetupDataPkg/Docs/PlatformIntegration/PlatformIntegrationSteps.md

@@ -214,6 +214,12 @@ Remove the FDF sections below.
   # INF MdeModulePkg/Application/UiApp/UiApp.inf
 ```
 
+### Standalone MM Configuration
+
+This repository also supports configuration in standalone MM. The expectation is that a separate configuration XML is
+used for standalone MM vs PEI/DXE, which produces separate autogenerated headers. All information in this document
+is valid, but substitute the standalone MM modules (e.g. ConfigKnobShimLibStandaloneMm) in place of the PEI/DXE ones.
+
 ## Profiles Integration
 
 In order to use configuration profiles, the platform must include the above changes as well as csv change files for

SetupDataPkg/Library/ConfigKnobShimLib/ConfigKnobShimDxeLib/ConfigKnobShimDxeLib.c

@@ -12,7 +12,7 @@
 
 /**
   GetConfigKnobFromVariable returns the configuration knob from variable storage if it exists. This function is
-  abstracted to work with both DXE and PEI.
+  abstracted to work with PEI, DXE, and Standalone MM.
 
   This function is only expected to be called by GetConfigKnobOverride.
 

SetupDataPkg/Library/ConfigKnobShimLib/ConfigKnobShimDxeLib/UnitTest/ConfigKnobShimDxeLibUnitTest.inf

@@ -1,13 +1,13 @@
 ## @file
-# Unit tests of the ConfigKnobShimExampleDxeLib instance.
+# Unit tests of the ConfigKnobShimDxeLib instance.
 #
 # Copyright (c) Microsoft Corporation.
 # SPDX-License-Identifier: BSD-2-Clause-Patent
 ##
 
 [Defines]
   INF_VERSION                    = 0x00010006
-  BASE_NAME                      = ConfigKnobShimExampleDxeUnitTest
+  BASE_NAME                      = ConfigKnobShimDxeUnitTest
   FILE_GUID                      = 215C2769-14FA-448A-82F3-0B62D968CE84
   MODULE_TYPE                    = HOST_APPLICATION
   VERSION_STRING                 = 1.0

SetupDataPkg/Library/ConfigKnobShimLib/ConfigKnobShimLibCommon.h

@@ -11,7 +11,7 @@
 
 /**
   GetConfigKnobFromVariable returns the configuration knob from variable storage if it exists. This function is
-  abstracted to work with both DXE and PEI.
+  abstracted to work with PEI, DXE, and Standalone MM.
 
   This function is only expected to be called by GetConfigKnob, via the autogen header code for config knobs.
 

SetupDataPkg/Library/ConfigKnobShimLib/ConfigKnobShimPeiLib/ConfigKnobShimPeiLib.c

@@ -16,7 +16,7 @@
 
 /**
   GetConfigKnobFromVariable returns the configuration knob from variable storage if it exists. This function is
-  abstracted to work with both DXE and PEI.
+  abstracted to work with PEI, DXE, and Standalone MM.
 
   This function is only expected to be called by GetConfigKnobOverride.
 

SetupDataPkg/Library/ConfigKnobShimLib/ConfigKnobShimPeiLib/UnitTest/ConfigKnobShimPeiLibUnitTest.inf

@@ -1,13 +1,13 @@
 ## @file
-# Unit tests of the ConfigKnobShimExamplePeiLib instance.
+# Unit tests of the ConfigKnobShimPeiLib instance.
 #
 # Copyright (c) Microsoft Corporation.
 # SPDX-License-Identifier: BSD-2-Clause-Patent
 ##
 
 [Defines]
   INF_VERSION                    = 0x00010006
-  BASE_NAME                      = ConfigKnobShimExamplePeiUnitTest
+  BASE_NAME                      = ConfigKnobShimPeiUnitTest
   FILE_GUID                      = 94116449-0814-4312-9DF6-1DAE4408D1BC
   MODULE_TYPE                    = HOST_APPLICATION
   VERSION_STRING                 = 1.0

SetupDataPkg/Library/ConfigKnobShimLib/ConfigKnobShimStandaloneMmLib/ConfigKnobShimStandaloneMmLib.c

@@ -0,0 +1,80 @@
+/** @file ConfigKnobShimStandaloneMmLib.c
+  Library interface for an OEM config policy creator to call into to fetch overrides for config values.
+
+  Copyright (c) Microsoft Corporation.
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+#include <PiPei.h>
+#include <Uefi.h>
+#include <Library/BaseLib.h>
+#include <Library/DebugLib.h>
+#include <Library/PeiServicesLib.h>
+#include <Library/MmServicesTableLib.h>
+#include <Protocol/SmmVariable.h>
+
+#include "../ConfigKnobShimLibCommon.h"
+
+/**
+  GetConfigKnobFromVariable returns the configuration knob from variable storage if it exists. This function is
+  abstracted to work with PEI, DXE, and Standalone MM.
+
+  This function is only expected to be called by GetConfigKnobOverride.
+
+  @param[in]  ConfigKnobGuid        The GUID of the requested config knob.
+  @param[in]  ConfigKnobName        The name of the requested config knob.
+  @param[out] ConfigKnobData        The retrieved data of the requested config knob. The caller will allocate memory for
+                                    this buffer and is responsible for freeing it. This parameter is acceptable to be
+                                    NULL if the data size is all that is requested.
+  @param[in out] ConfigKnobDataSize The allocated size of ConfigKnobData. This is expected to be set to the correct
+                                    value for the size of ConfigKnobData. If this size is too small for the config knob,
+                                    EFI_BUFFER_TOO_SMALL will be returned. This represents a mismatch in the profile
+                                    expected size and what is stored in variable storage, so the profile value will
+                                    take precedence.
+
+  @retval EFI_NOT_FOUND           The requested config knob was not found in the policy cache or variable storage. This
+                                  is expected when the config knob has not been updated from the profile default.
+  @retval EFI_BUFFER_TOO_SMALL    ConfigKnobDataSize as passed in was too small for this config knob. This is expected
+                                  if stale variables exist in flash.
+  @retval EFI_NOT_READY           Variable Services not available.
+  @retval !EFI_SUCCESS            Failed to read variable from variable storage.
+  @retval EFI_SUCCESS             The operation succeeds.
+
+**/
+EFI_STATUS
+GetConfigKnobFromVariable (
+  IN EFI_GUID   *ConfigKnobGuid,
+  IN CHAR16     *ConfigKnobName,
+  OUT VOID      *ConfigKnobData,
+  IN OUT UINTN  *ConfigKnobDataSize
+  )
+{
+  EFI_STATUS                 Status;
+  EFI_SMM_VARIABLE_PROTOCOL  *MmVariableServices;
+
+  Status = gMmst->MmLocateProtocol (
+                    &gEfiSmmVariableProtocolGuid,
+                    NULL,
+                    (VOID **)&MmVariableServices
+                    );
+
+  if (EFI_ERROR (Status)) {
+    DEBUG ((
+      DEBUG_ERROR,
+      "%a: Failed to locate variable services with status %r, falling back to profile value for config knob %a\n",
+      __FUNCTION__,
+      Status,
+      ConfigKnobName
+      ));
+
+    return Status;
+  }
+
+  return MmVariableServices->SmmGetVariable (
+                               ConfigKnobName,
+                               ConfigKnobGuid,
+                               NULL,
+                               ConfigKnobDataSize,
+                               ConfigKnobData
+                               );
+}

SetupDataPkg/Library/ConfigKnobShimLib/ConfigKnobShimStandaloneMmLib/ConfigKnobShimStandaloneMmLib.inf

@@ -0,0 +1,46 @@
+## @file
+# Library interface for an OEM config policy creator to call into to fetch overrides for config values.
+#
+# Copyright (c) Microsoft Corporation
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+##
+
+[Defines]
+  INF_VERSION               = 0x00010017
+  BASE_NAME                 = ConfigKnobShimStandaloneMmLib
+  FILE_GUID                 = 675EE92E-8771-413A-8BBE-B87152B910E2
+  VERSION_STRING            = 1.0
+  MODULE_TYPE               = MM_STANDALONE
+  LIBRARY_CLASS             = ConfigKnobShimLib
+  PI_SPECIFICATION_VERSION  = 0x00010032
+
+#
+# The following information is for reference only and not required by the
+# build tools.
+#
+#  VALID_ARCHITECTURES           = IA32 X64 AARCH64
+#
+
+[Sources]
+  ConfigKnobShimStandaloneMmLib.c
+  ../ConfigKnobShimLibCommon.c
+  ../ConfigKnobShimLibCommon.h
+
+[Packages]
+  MdePkg/MdePkg.dec
+  MdeModulePkg/MdeModulePkg.dec
+  SetupDataPkg/SetupDataPkg.dec
+
+[LibraryClasses]
+  BaseLib
+  DebugLib
+  BaseMemoryLib
+  MmServicesTableLib
+
+[Protocols]
+  gEfiSmmVariableProtocolGuid ## CONSUMES
+
+[Depex]
+  # Platforms can decide whether variable services are a requirement for config or not
+  gEfiSmmVariableProtocolGuid

SetupDataPkg/Library/ConfigKnobShimLib/ConfigKnobShimStandaloneMmLib/UnitTest/ConfigKnobShimStandaloneMmLibUnitTest.inf

@@ -0,0 +1,40 @@
+## @file
+# Unit tests of the ConfigKnobShimExampleStandaloneMmLib instance.
+#
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010017
+  BASE_NAME                      = ConfigKnobShimStandaloneMmUnitTest
+  FILE_GUID                      = EA4B9417-78FC-474E-AC35-44AFF09E9099
+  MODULE_TYPE                    = HOST_APPLICATION
+  VERSION_STRING                 = 1.0
+
+#
+# The following information is for reference only and not required by the build tools.
+#
+#  VALID_ARCHITECTURES           = IA32 X64 AARCH64
+#
+
+[Sources]
+  ../../UnitTest/ConfigKnobShimLibUnitTestCommon.c
+  ../ConfigKnobShimStandaloneMmLib.c
+  ../../ConfigKnobShimLibCommon.c
+
+[Packages]
+  MdePkg/MdePkg.dec
+  MdeModulePkg/MdeModulePkg.dec
+  UnitTestFrameworkPkg/UnitTestFrameworkPkg.dec
+  SetupDataPkg/SetupDataPkg.dec
+
+[LibraryClasses]
+  BaseLib
+  BaseMemoryLib
+  DebugLib
+  MmServicesTableLib
+  UnitTestLib
+
+[Protocols]
+  gEfiSmmVariableProtocolGuid    ## CONSUMES