[edk2-devel] [PATCH V2 28/32] AMD/VanGoghBoard: Check in SmmCpuFeaturesLibCommon module.

["Zhai, MingXin (Duke) via groups.io" <duke.zhai=amd.com@groups.io>]

From: Duke Zhai <Duke.Zhai@amd.com>

BZ #:4640
In V2: Improve coding style.
  1.Remove the leading underscore and use double underscore at trailing in C header files.
  2.Remove old tianocore licenses and redundant license description.
  3.Improve coding style. For example: remove space between @param.

In V1:
  Initial SmmCpuFeaturesLibCommon module. The CPU specific programming for
  PiSmmCpuDxeSmm module when STM support is not included.

Signed-off-by: Duke Zhai <duke.zhai@amd.com>
Cc: Eric Xing <eric.xing@amd.com>
Cc: Ken Yao <ken.yao@amd.com>
Cc: Igniculus Fu <igniculus.fu@amd.com>
Cc: Abner Chang <abner.chang@amd.com>
---
 .../SmmCpuFeaturesLibCommon.c                 | 623 ++++++++++++++++++
 1 file changed, 623 insertions(+)
 create mode 100644 Platform/AMD/VanGoghBoard/Override/edk2/UefiCpuPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLibCommon.c

diff --git a/Platform/AMD/VanGoghBoard/Override/edk2/UefiCpuPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLibCommon.c b/Platform/AMD/VanGoghBoard/Override/edk2/UefiCpuPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLibCommon.c
new file mode 100644
index 0000000000..f3615e2d9e
--- /dev/null
+++ b/Platform/AMD/VanGoghBoard/Override/edk2/UefiCpuPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLibCommon.c
@@ -0,0 +1,623 @@
+/** @file
+Implementation shared across all library instances.
+
+Copyright (C) 2024 Advanced Micro Devices, Inc. All rights reserved.<BR>
+Copyright (c) 2010 - 2019, Intel Corporation. All rights reserved.<BR>
+Copyright (c) Microsoft Corporation.<BR>
+SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <PiMm.h>
+#include <Library/SmmCpuFeaturesLib.h>
+#include <Library/BaseLib.h>
+#include <Library/MtrrLib.h>
+#include <Library/PcdLib.h>
+#include <Library/MemoryAllocationLib.h>
+#include <Library/DebugLib.h>
+#include <Register/Intel/Cpuid.h>
+#include <Register/Intel/SmramSaveStateMap.h>
+#include "CpuFeaturesLib.h"
+
+//
+// Machine Specific Registers (MSRs)
+//
+#define  SMM_FEATURES_LIB_IA32_MTRR_CAP            0x0FE
+#define  SMM_FEATURES_LIB_IA32_FEATURE_CONTROL     0x03A
+#define  SMM_FEATURES_LIB_IA32_SMRR_PHYSBASE       0x1F2
+#define  SMM_FEATURES_LIB_IA32_SMRR_PHYSMASK       0x1F3
+#define  SMM_FEATURES_LIB_IA32_CORE_SMRR_PHYSBASE  0x0A0
+#define  SMM_FEATURES_LIB_IA32_CORE_SMRR_PHYSMASK  0x0A1
+#define    EFI_MSR_SMRR_MASK                       0xFFFFF000
+#define    EFI_MSR_SMRR_PHYS_MASK_VALID            BIT11
+#define  SMM_FEATURES_LIB_SMM_FEATURE_CONTROL      0x4E0
+
+//
+// MSRs required for configuration of SMM Code Access Check
+//
+#define SMM_FEATURES_LIB_IA32_MCA_CAP  0x17D
+#define   SMM_CODE_ACCESS_CHK_BIT      BIT58
+
+extern UINT8  mSmmSaveStateRegisterLma;
+
+//
+// Set default value to assume SMRR is not supported
+//
+BOOLEAN  mSmrrSupported = FALSE;
+
+//
+// Set default value to assume MSR_SMM_FEATURE_CONTROL is not supported
+//
+BOOLEAN  mSmmFeatureControlSupported = FALSE;
+
+//
+// Set default value to assume IA-32 Architectural MSRs are used
+//
+UINT32  mSmrrPhysBaseMsr = SMM_FEATURES_LIB_IA32_SMRR_PHYSBASE;
+UINT32  mSmrrPhysMaskMsr = SMM_FEATURES_LIB_IA32_SMRR_PHYSMASK;
+
+//
+// Set default value to assume MTRRs need to be configured on each SMI
+//
+BOOLEAN  mNeedConfigureMtrrs = TRUE;
+
+//
+// Array for state of SMRR enable on all CPUs
+//
+BOOLEAN  *mSmrrEnabled;
+
+/**
+  Performs library initialization.
+
+  This initialization function contains common functionality shared betwen all
+  library instance constructors.
+
+**/
+VOID
+CpuFeaturesLibInitialization (
+  VOID
+  )
+{
+  UINT32  RegEax;
+  UINT32  RegEdx;
+  UINTN   FamilyId;
+  UINTN   ModelId;
+
+  //
+  // Retrieve CPU Family and Model
+  //
+  AsmCpuid (CPUID_VERSION_INFO, &RegEax, NULL, NULL, &RegEdx);
+  FamilyId = (RegEax >> 8) & 0xf;
+  ModelId  = (RegEax >> 4) & 0xf;
+  if ((FamilyId == 0x06) || (FamilyId == 0x0f)) {
+    ModelId = ModelId | ((RegEax >> 12) & 0xf0);
+  }
+
+  //
+  // Check CPUID(CPUID_VERSION_INFO).EDX[12] for MTRR capability
+  //
+  if ((RegEdx & BIT12) != 0) {
+    //
+    // Check MTRR_CAP MSR bit 11 for SMRR support
+    //
+    if ((AsmReadMsr64 (SMM_FEATURES_LIB_IA32_MTRR_CAP) & BIT11) != 0) {
+      mSmrrSupported = TRUE;
+    }
+  }
+
+  //
+  // Intel(R) 64 and IA-32 Architectures Software Developer's Manual
+  // Volume 3C, Section 35.3 MSRs in the Intel(R) Atom(TM) Processor Family
+  //
+  // If CPU Family/Model is 06_1CH, 06_26H, 06_27H, 06_35H or 06_36H, then
+  // SMRR Physical Base and SMM Physical Mask MSRs are not available.
+  //
+  if (FamilyId == 0x06) {
+    if ((ModelId == 0x1C) || (ModelId == 0x26) || (ModelId == 0x27) || (ModelId == 0x35) || (ModelId == 0x36)) {
+      mSmrrSupported = FALSE;
+    }
+  }
+
+  //
+  // Intel(R) 64 and IA-32 Architectures Software Developer's Manual
+  // Volume 3C, Section 35.2 MSRs in the Intel(R) Core(TM) 2 Processor Family
+  //
+  // If CPU Family/Model is 06_0F or 06_17, then use Intel(R) Core(TM) 2
+  // Processor Family MSRs
+  //
+  if (FamilyId == 0x06) {
+    if ((ModelId == 0x17) || (ModelId == 0x0f)) {
+      mSmrrPhysBaseMsr = SMM_FEATURES_LIB_IA32_CORE_SMRR_PHYSBASE;
+      mSmrrPhysMaskMsr = SMM_FEATURES_LIB_IA32_CORE_SMRR_PHYSMASK;
+    }
+  }
+
+  //
+  // Intel(R) 64 and IA-32 Architectures Software Developer's Manual
+  // Volume 3C, Section 34.4.2 SMRAM Caching
+  //   An IA-32 processor does not automatically write back and invalidate its
+  //   caches before entering SMM or before exiting SMM. Because of this behavior,
+  //   care must be taken in the placement of the SMRAM in system memory and in
+  //   the caching of the SMRAM to prevent cache incoherence when switching back
+  //   and forth between SMM and protected mode operation.
+  //
+  // An IA-32 processor is a processor that does not support the Intel 64
+  // Architecture.  Support for the Intel 64 Architecture can be detected from
+  // CPUID(CPUID_EXTENDED_CPU_SIG).EDX[29]
+  //
+  // If an IA-32 processor is detected, then set mNeedConfigureMtrrs to TRUE,
+  // so caches are flushed on SMI entry and SMI exit, the interrupted code
+  // MTRRs are saved/restored, and MTRRs for SMM are loaded.
+  //
+  AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
+  if (RegEax >= CPUID_EXTENDED_CPU_SIG) {
+    AsmCpuid (CPUID_EXTENDED_CPU_SIG, NULL, NULL, NULL, &RegEdx);
+    if ((RegEdx & BIT29) != 0) {
+      mNeedConfigureMtrrs = FALSE;
+    }
+  }
+
+  //
+  // Allocate array for state of SMRR enable on all CPUs
+  //
+  mSmrrEnabled = (BOOLEAN *)AllocatePool (sizeof (BOOLEAN) * GetCpuMaxLogicalProcessorNumber ());
+  ASSERT (mSmrrEnabled != NULL);
+}
+
+/**
+  Called during the very first SMI into System Management Mode to initialize
+  CPU features, including SMBASE, for the currently executing CPU.  Since this
+  is the first SMI, the SMRAM Save State Map is at the default address of
+  SMM_DEFAULT_SMBASE + SMRAM_SAVE_STATE_MAP_OFFSET.  The currently executing
+  CPU is specified by CpuIndex and CpuIndex can be used to access information
+  about the currently executing CPU in the ProcessorInfo array and the
+  HotPlugCpuData data structure.
+
+  @param[in] CpuIndex        The index of the CPU to initialize.  The value
+                             must be between 0 and the NumberOfCpus field in
+                             the System Management System Table (SMST).
+  @param[in] IsMonarch       TRUE if the CpuIndex is the index of the CPU that
+                             was elected as monarch during System Management
+                             Mode initialization.
+                             FALSE if the CpuIndex is not the index of the CPU
+                             that was elected as monarch during System
+                             Management Mode initialization.
+  @param[in] ProcessorInfo   Pointer to an array of EFI_PROCESSOR_INFORMATION
+                             structures.  ProcessorInfo[CpuIndex] contains the
+                             information for the currently executing CPU.
+  @param[in] CpuHotPlugData  Pointer to the CPU_HOT_PLUG_DATA structure that
+                             contains the ApidId and SmBase arrays.
+**/
+VOID
+EFIAPI
+SmmCpuFeaturesInitializeProcessor (
+  IN UINTN                      CpuIndex,
+  IN BOOLEAN                    IsMonarch,
+  IN EFI_PROCESSOR_INFORMATION  *ProcessorInfo,
+  IN CPU_HOT_PLUG_DATA          *CpuHotPlugData
+  )
+{
+  SMRAM_SAVE_STATE_MAP  *CpuState;
+  UINT64                FeatureControl;
+  UINT32                RegEax;
+  UINT32                RegEdx;
+  UINTN                 FamilyId;
+  UINTN                 ModelId;
+
+  //
+  // Configure SMBASE.
+  //
+  CpuState = (SMRAM_SAVE_STATE_MAP *)(UINTN)(SMM_DEFAULT_SMBASE + SMRAM_SAVE_STATE_MAP_OFFSET);
+  if (mSmmSaveStateRegisterLma == EFI_SMM_SAVE_STATE_REGISTER_LMA_32BIT) {
+    CpuState->x86.SMBASE = (UINT32)CpuHotPlugData->SmBase[CpuIndex];
+  } else {
+    CpuState->x64.SMBASE = (UINT32)CpuHotPlugData->SmBase[CpuIndex];
+  }
+
+  //
+  // Intel(R) 64 and IA-32 Architectures Software Developer's Manual
+  // Volume 3C, Section 35.2 MSRs in the Intel(R) Core(TM) 2 Processor Family
+  //
+  // If Intel(R) Core(TM) Core(TM) 2 Processor Family MSRs are being used, then
+  // make sure SMRR Enable(BIT3) of MSR_FEATURE_CONTROL MSR(0x3A) is set before
+  // accessing SMRR base/mask MSRs.  If Lock(BIT0) of MSR_FEATURE_CONTROL MSR(0x3A)
+  // is set, then the MSR is locked and can not be modified.
+  //
+  if (mSmrrSupported && (mSmrrPhysBaseMsr == SMM_FEATURES_LIB_IA32_CORE_SMRR_PHYSBASE)) {
+    FeatureControl = AsmReadMsr64 (SMM_FEATURES_LIB_IA32_FEATURE_CONTROL);
+    if ((FeatureControl & BIT3) == 0) {
+      if ((FeatureControl & BIT0) == 0) {
+        AsmWriteMsr64 (SMM_FEATURES_LIB_IA32_FEATURE_CONTROL, FeatureControl | BIT3);
+      } else {
+        mSmrrSupported = FALSE;
+      }
+    }
+  }
+
+  //
+  // If SMRR is supported, then program SMRR base/mask MSRs.
+  // The EFI_MSR_SMRR_PHYS_MASK_VALID bit is not set until the first normal SMI.
+  // The code that initializes SMM environment is running in normal mode
+  // from SMRAM region.  If SMRR is enabled here, then the SMRAM region
+  // is protected and the normal mode code execution will fail.
+  //
+  if (mSmrrSupported) {
+    //
+    // SMRR size cannot be less than 4-KBytes
+    // SMRR size must be of length 2^n
+    // SMRR base alignment cannot be less than SMRR length
+    //
+    if ((CpuHotPlugData->SmrrSize < SIZE_4KB) ||
+        (CpuHotPlugData->SmrrSize != GetPowerOfTwo32 (CpuHotPlugData->SmrrSize)) ||
+        ((CpuHotPlugData->SmrrBase & ~(CpuHotPlugData->SmrrSize - 1)) != CpuHotPlugData->SmrrBase))
+    {
+      //
+      // Print message and halt if CPU is Monarch
+      //
+      if (IsMonarch) {
+        DEBUG ((DEBUG_ERROR, "SMM Base/Size does not meet alignment/size requirement!\n"));
+        CpuDeadLoop ();
+      }
+    } else {
+      AsmWriteMsr64 (mSmrrPhysBaseMsr, CpuHotPlugData->SmrrBase | MTRR_CACHE_WRITE_BACK);
+      AsmWriteMsr64 (mSmrrPhysMaskMsr, (~(CpuHotPlugData->SmrrSize - 1) & EFI_MSR_SMRR_MASK));
+      mSmrrEnabled[CpuIndex] = FALSE;
+    }
+  }
+
+  //
+  // Retrieve CPU Family and Model
+  //
+  AsmCpuid (CPUID_VERSION_INFO, &RegEax, NULL, NULL, &RegEdx);
+  FamilyId = (RegEax >> 8) & 0xf;
+  ModelId  = (RegEax >> 4) & 0xf;
+  if ((FamilyId == 0x06) || (FamilyId == 0x0f)) {
+    ModelId = ModelId | ((RegEax >> 12) & 0xf0);
+  }
+
+  //
+  // Intel(R) 64 and IA-32 Architectures Software Developer's Manual
+  // Volume 3C, Section 35.10.1 MSRs in 4th Generation Intel(R) Core(TM)
+  // Processor Family.
+  //
+  // If CPU Family/Model is 06_3C, 06_45, or 06_46 then use 4th Generation
+  // Intel(R) Core(TM) Processor Family MSRs.
+  //
+  if (FamilyId == 0x06) {
+    if ((ModelId == 0x3C) || (ModelId == 0x45) || (ModelId == 0x46) ||
+        (ModelId == 0x3D) || (ModelId == 0x47) || (ModelId == 0x4E) || (ModelId == 0x4F) ||
+        (ModelId == 0x3F) || (ModelId == 0x56) || (ModelId == 0x57) || (ModelId == 0x5C) ||
+        (ModelId == 0x8C))
+    {
+      //
+      // Check to see if the CPU supports the SMM Code Access Check feature
+      // Do not access this MSR unless the CPU supports the SmmRegFeatureControl
+      //
+      if ((AsmReadMsr64 (SMM_FEATURES_LIB_IA32_MCA_CAP) & SMM_CODE_ACCESS_CHK_BIT) != 0) {
+        mSmmFeatureControlSupported = TRUE;
+      }
+    }
+  }
+
+  //
+  //  Call internal worker function that completes the CPU initialization
+  //
+  FinishSmmCpuFeaturesInitializeProcessor ();
+}
+
+/**
+  This function updates the SMRAM save state on the currently executing CPU
+  to resume execution at a specific address after an RSM instruction.  This
+  function must evaluate the SMRAM save state to determine the execution mode
+  the RSM instruction resumes and update the resume execution address with
+  either NewInstructionPointer32 or NewInstructionPoint.  The auto HALT restart
+  flag in the SMRAM save state must always be cleared.  This function returns
+  the value of the instruction pointer from the SMRAM save state that was
+  replaced.  If this function returns 0, then the SMRAM save state was not
+  modified.
+
+  This function is called during the very first SMI on each CPU after
+  SmmCpuFeaturesInitializeProcessor() to set a flag in normal execution mode
+  to signal that the SMBASE of each CPU has been updated before the default
+  SMBASE address is used for the first SMI to the next CPU.
+
+  @param[in] CpuIndex                 The index of the CPU to hook.  The value
+                                      must be between 0 and the NumberOfCpus
+                                      field in the System Management System Table
+                                      (SMST).
+  @param[in] CpuState                 Pointer to SMRAM Save State Map for the
+                                      currently executing CPU.
+  @param[in] NewInstructionPointer32  Instruction pointer to use if resuming to
+                                      32-bit execution mode from 64-bit SMM.
+  @param[in] NewInstructionPointer    Instruction pointer to use if resuming to
+                                      same execution mode as SMM.
+
+  @retval 0    This function did modify the SMRAM save state.
+  @retval > 0  The original instruction pointer value from the SMRAM save state
+               before it was replaced.
+**/
+UINT64
+EFIAPI
+SmmCpuFeaturesHookReturnFromSmm (
+  IN UINTN                 CpuIndex,
+  IN SMRAM_SAVE_STATE_MAP  *CpuState,
+  IN UINT64                NewInstructionPointer32,
+  IN UINT64                NewInstructionPointer
+  )
+{
+  return 0;
+}
+
+/**
+  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
+  )
+{
+}
+
+/**
+  Determines if MTRR registers must be configured to set SMRAM cache-ability
+  when executing in System Management Mode.
+
+  @retval TRUE   MTRR registers must be configured to set SMRAM cache-ability.
+  @retval FALSE  MTRR registers do not need to be configured to set SMRAM
+                 cache-ability.
+**/
+BOOLEAN
+EFIAPI
+SmmCpuFeaturesNeedConfigureMtrrs (
+  VOID
+  )
+{
+  return mNeedConfigureMtrrs;
+}
+
+/**
+  Disable SMRR register if SMRR is supported and SmmCpuFeaturesNeedConfigureMtrrs()
+  returns TRUE.
+**/
+VOID
+EFIAPI
+SmmCpuFeaturesDisableSmrr (
+  VOID
+  )
+{
+  if (mSmrrSupported && mNeedConfigureMtrrs) {
+    AsmWriteMsr64 (mSmrrPhysMaskMsr, AsmReadMsr64 (mSmrrPhysMaskMsr) & ~EFI_MSR_SMRR_PHYS_MASK_VALID);
+  }
+}
+
+/**
+  Enable SMRR register if SMRR is supported and SmmCpuFeaturesNeedConfigureMtrrs()
+  returns TRUE.
+**/
+VOID
+EFIAPI
+SmmCpuFeaturesReenableSmrr (
+  VOID
+  )
+{
+  if (mSmrrSupported && mNeedConfigureMtrrs) {
+    AsmWriteMsr64 (mSmrrPhysMaskMsr, AsmReadMsr64 (mSmrrPhysMaskMsr) | EFI_MSR_SMRR_PHYS_MASK_VALID);
+  }
+}
+
+/**
+  Processor specific hook point each time a CPU enters System Management Mode.
+
+  @param[in] CpuIndex  The index of the CPU that has entered SMM.  The value
+                       must be between 0 and the NumberOfCpus field in the
+                       System Management System Table (SMST).
+**/
+VOID
+EFIAPI
+SmmCpuFeaturesRendezvousEntry (
+  IN UINTN  CpuIndex
+  )
+{
+  //
+  // If SMRR is supported and this is the first normal SMI, then enable SMRR
+  //
+  if (mSmrrSupported && !mSmrrEnabled[CpuIndex]) {
+    AsmWriteMsr64 (mSmrrPhysMaskMsr, AsmReadMsr64 (mSmrrPhysMaskMsr) | EFI_MSR_SMRR_PHYS_MASK_VALID);
+    mSmrrEnabled[CpuIndex] = TRUE;
+  }
+}
+
+/**
+  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
+  )
+{
+}
+
+/**
+  Check to see if an SMM register is supported by a specified CPU.
+
+  @param[in] CpuIndex  The index of the CPU to check for SMM register support.
+                       The value must be between 0 and the NumberOfCpus field
+                       in the System Management System Table (SMST).
+  @param[in] RegName   Identifies the SMM register to check for support.
+
+  @retval TRUE   The SMM register specified by RegName is supported by the CPU
+                 specified by CpuIndex.
+  @retval FALSE  The SMM register specified by RegName is not supported by the
+                 CPU specified by CpuIndex.
+**/
+BOOLEAN
+EFIAPI
+SmmCpuFeaturesIsSmmRegisterSupported (
+  IN UINTN         CpuIndex,
+  IN SMM_REG_NAME  RegName
+  )
+{
+  if (mSmmFeatureControlSupported && (RegName == SmmRegFeatureControl)) {
+    return TRUE;
+  }
+
+  return FALSE;
+}
+
+/**
+  Returns the current value of the SMM register for the specified CPU.
+  If the SMM register is not supported, then 0 is returned.
+
+  @param[in] CpuIndex  The index of the CPU to read the SMM register.  The
+                       value must be between 0 and the NumberOfCpus field in
+                       the System Management System Table (SMST).
+  @param[in] RegName   Identifies the SMM register to read.
+
+  @return  The value of the SMM register specified by RegName from the CPU
+           specified by CpuIndex.
+**/
+UINT64
+EFIAPI
+SmmCpuFeaturesGetSmmRegister (
+  IN UINTN         CpuIndex,
+  IN SMM_REG_NAME  RegName
+  )
+{
+  if (mSmmFeatureControlSupported && (RegName == SmmRegFeatureControl)) {
+    return AsmReadMsr64 (SMM_FEATURES_LIB_SMM_FEATURE_CONTROL);
+  }
+
+  return 0;
+}
+
+/**
+  Sets the value of an SMM register on a specified CPU.
+  If the SMM register is not supported, then no action is performed.
+
+  @param[in] CpuIndex  The index of the CPU to write the SMM register.  The
+                       value must be between 0 and the NumberOfCpus field in
+                       the System Management System Table (SMST).
+  @param[in] RegName   Identifies the SMM register to write.
+                       registers are read-only.
+  @param[in] Value     The value to write to the SMM register.
+**/
+VOID
+EFIAPI
+SmmCpuFeaturesSetSmmRegister (
+  IN UINTN         CpuIndex,
+  IN SMM_REG_NAME  RegName,
+  IN UINT64        Value
+  )
+{
+  if (mSmmFeatureControlSupported && (RegName == SmmRegFeatureControl)) {
+    AsmWriteMsr64 (SMM_FEATURES_LIB_SMM_FEATURE_CONTROL, Value);
+  }
+}
+
+/**
+  Read an SMM Save State register on the target processor.  If this function
+  returns EFI_UNSUPPORTED, then the caller is responsible for reading the
+  SMM Save Sate register.
+
+  @param[in]  CpuIndex  The index of the CPU to read the SMM Save State.  The
+                        value must be between 0 and the NumberOfCpus field in
+                        the System Management System Table (SMST).
+  @param[in]  Register  The SMM Save State register to read.
+  @param[in]  Width     The number of bytes to read from the CPU save state.
+  @param[out] Buffer    Upon return, this holds the CPU register value read
+                        from the save state.
+
+  @retval EFI_SUCCESS           The register was read from Save State.
+  @retval EFI_INVALID_PARAMETER  Buffer is NULL.
+  @retval EFI_UNSUPPORTED       This function does not support reading Register.
+
+**/
+EFI_STATUS
+EFIAPI
+SmmCpuFeaturesReadSaveStateRegister (
+  IN  UINTN                        CpuIndex,
+  IN  EFI_SMM_SAVE_STATE_REGISTER  Register,
+  IN  UINTN                        Width,
+  OUT VOID                         *Buffer
+  )
+{
+  return EFI_UNSUPPORTED;
+}
+
+/**
+  Writes an SMM Save State register on the target processor.  If this function
+  returns EFI_UNSUPPORTED, then the caller is responsible for writing the
+  SMM Save Sate register.
+
+  @param[in] CpuIndex  The index of the CPU to write the SMM Save State.  The
+                       value must be between 0 and the NumberOfCpus field in
+                       the System Management System Table (SMST).
+  @param[in] Register  The SMM Save State register to write.
+  @param[in] Width     The number of bytes to write to the CPU save state.
+  @param[in] Buffer    Upon entry, this holds the new CPU register value.
+
+  @retval EFI_SUCCESS           The register was written to Save State.
+  @retval EFI_INVALID_PARAMETER  Buffer is NULL.
+  @retval EFI_UNSUPPORTED       This function does not support writing Register.
+**/
+EFI_STATUS
+EFIAPI
+SmmCpuFeaturesWriteSaveStateRegister (
+  IN UINTN                        CpuIndex,
+  IN EFI_SMM_SAVE_STATE_REGISTER  Register,
+  IN UINTN                        Width,
+  IN CONST VOID                   *Buffer
+  )
+{
+  return EFI_UNSUPPORTED;
+}
+
+/**
+  This function is hook point called after the gEfiSmmReadyToLockProtocolGuid
+  notification is completely processed.
+**/
+VOID
+EFIAPI
+SmmCpuFeaturesCompleteSmmReadyToLock (
+  VOID
+  )
+{
+}
+
+/**
+  This API provides a method for a CPU to allocate a specific region for storing page tables.
+
+  This API can be called more once to allocate memory for page tables.
+
+  Allocates the number of 4KB pages of type EfiRuntimeServicesData and returns a pointer to the
+  allocated buffer.  The buffer returned is aligned on a 4KB boundary.  If Pages is 0, then NULL
+  is returned.  If there is not enough memory remaining to satisfy the request, then NULL is
+  returned.
+
+  This function can also return NULL if there is no preference on where the page tables are allocated in SMRAM.
+
+  @param  Pages                 The number of 4 KB pages to allocate.
+
+  @return A pointer to the allocated buffer for page tables.
+  @retval NULL      Fail to allocate a specific region for storing page tables,
+                    Or there is no preference on where the page tables are allocated in SMRAM.
+
+**/
+VOID *
+EFIAPI
+SmmCpuFeaturesAllocatePageTableMemory (
+  IN UINTN  Pages
+  )
+{
+  return NULL;
+}
--
2.31.1



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