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audk/UefiCpuPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c

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/** @file
The CPU specific programming for PiSmmCpuDxeSmm module.
Copyright (c) 2010 - 2016, Intel Corporation. All rights reserved.<BR>
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 <PiSmm.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/Cpuid.h>
#include <Register/SmramSaveStateMap.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
//
// 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;
/**
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
SmmCpuFeaturesLibConstructor (
IN EFI_HANDLE ImageHandle,
IN EFI_SYSTEM_TABLE *SystemTable
)
{
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) * PcdGet32 (PcdCpuMaxLogicalProcessorNumber));
ASSERT (mSmrrEnabled != NULL);
return EFI_SUCCESS;
}
/**
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);
CpuState->x86.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 ((EFI_D_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) {
//
// 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;
}
}
}
}
/**
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
)
{
}
/**
Return the size, in bytes, of a custom SMI Handler in bytes. If 0 is
returned, then a custom SMI handler is not provided by this library,
and the default SMI handler must be used.
@retval 0 Use the default SMI handler.
@retval > 0 Use the SMI handler installed by SmmCpuFeaturesInstallSmiHandler()
The caller is required to allocate enough SMRAM for each CPU to
support the size of the custom SMI handler.
**/
UINTN
EFIAPI
SmmCpuFeaturesGetSmiHandlerSize (
VOID
)
{
return 0;
}
/**
Install a custom SMI handler for the CPU specified by CpuIndex. This function
is only called if SmmCpuFeaturesGetSmiHandlerSize() returns a size is greater
than zero and is called by the CPU that was elected as monarch during System
Management Mode initialization.
@param[in] CpuIndex The index of the CPU to install the custom SMI handler.
The value must be between 0 and the NumberOfCpus field
in the System Management System Table (SMST).
@param[in] SmBase The SMBASE address for the CPU specified by CpuIndex.
@param[in] SmiStack The stack to use when an SMI is processed by the
the CPU specified by CpuIndex.
@param[in] StackSize The size, in bytes, if the stack used when an SMI is
processed by the CPU specified by CpuIndex.
@param[in] GdtBase The base address of the GDT to use when an SMI is
processed by the CPU specified by CpuIndex.
@param[in] GdtSize The size, in bytes, of the GDT used when an SMI is
processed by the CPU specified by CpuIndex.
@param[in] IdtBase The base address of the IDT to use when an SMI is
processed by the CPU specified by CpuIndex.
@param[in] IdtSize The size, in bytes, of the IDT used when an SMI is
processed by the CPU specified by CpuIndex.
@param[in] Cr3 The base address of the page tables to use when an SMI
is processed by the CPU specified by CpuIndex.
**/
VOID
EFIAPI
SmmCpuFeaturesInstallSmiHandler (
IN UINTN CpuIndex,
IN UINT32 SmBase,
IN VOID *SmiStack,
IN UINTN StackSize,
IN UINTN GdtBase,
IN UINTN GdtSize,
IN UINTN IdtBase,
IN UINTN IdtSize,
IN UINT32 Cr3
)
{
}
/**
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_PARAMTER 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_PARAMTER 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;
}
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