text: /** @file
    Local APIC Library.
  
    This local APIC library instance supports x2APIC capable processors
    which have xAPIC and x2APIC modes.
  
    Copyright (c) 2010 - 2019, Intel Corporation. All rights reserved.<BR>
    Copyright (c) 2017 - 2020, AMD Inc. All rights reserved.<BR>
  
    SPDX-License-Identifier: BSD-2-Clause-Patent
  
  **/
  
  #include <Register/Intel/Cpuid.h>
  #include <Register/Amd/Cpuid.h>
  #include <Register/Intel/Msr.h>
  #include <Register/Intel/LocalApic.h>
  
  #include <Library/BaseLib.h>
  #include <Library/DebugLib.h>
  #include <Library/LocalApicLib.h>
  #include <Library/IoLib.h>
  #include <Library/TimerLib.h>
  #include <Library/PcdLib.h>
  #include <Library/UefiCpuLib.h>
  
  //
  // Library internal functions
  //
  
  /**
    Determine if the CPU supports the Local APIC Base Address MSR.
  
    @retval TRUE  The CPU supports the Local APIC Base Address MSR.
    @retval FALSE The CPU does not support the Local APIC Base Address MSR.
  
  **/
  BOOLEAN
  LocalApicBaseAddressMsrSupported (
    VOID
    )
  {
    UINT32  RegEax;
    UINTN   FamilyId;
  
    AsmCpuid (1, &RegEax, NULL, NULL, NULL);
    FamilyId = BitFieldRead32 (RegEax, 8, 11);
    if (FamilyId == 0x04 || FamilyId == 0x05) {
      //
      // CPUs with a FamilyId of 0x04 or 0x05 do not support the
      // Local APIC Base Address MSR
      //
      return FALSE;
    }
    return TRUE;
  }
  
  /**
    Retrieve the base address of local APIC.
  
    @return The base address of local APIC.
  
  **/
  UINTN
  EFIAPI
  GetLocalApicBaseAddress (
    VOID
    )
  {
    MSR_IA32_APIC_BASE_REGISTER  ApicBaseMsr;
  
    if (!LocalApicBaseAddressMsrSupported ()) {
      //
      // If CPU does not support Local APIC Base Address MSR, then retrieve
      // Local APIC Base Address from PCD
      //
      return PcdGet32 (PcdCpuLocalApicBaseAddress);
    }
  
    ApicBaseMsr.Uint64 = AsmReadMsr64 (MSR_IA32_APIC_BASE);
  
    return (UINTN)(LShiftU64 ((UINT64) ApicBaseMsr.Bits.ApicBaseHi, 32)) +
             (((UINTN)ApicBaseMsr.Bits.ApicBase) << 12);
  }
  
  /**
    Set the base address of local APIC.
  
    If BaseAddress is not aligned on a 4KB boundary, then ASSERT().
  
    @param[in] BaseAddress   Local APIC base address to be set.
  
  **/
  VOID
  EFIAPI
  SetLocalApicBaseAddress (
    IN UINTN                BaseAddress
    )
  {
    MSR_IA32_APIC_BASE_REGISTER  ApicBaseMsr;
  
    ASSERT ((BaseAddress & (SIZE_4KB - 1)) == 0);
  
    if (!LocalApicBaseAddressMsrSupported ()) {
      //
      // Ignore set request of the CPU does not support APIC Base Address MSR
      //
      return;
    }
  
    ApicBaseMsr.Uint64 = AsmReadMsr64 (MSR_IA32_APIC_BASE);
  
    ApicBaseMsr.Bits.ApicBase   = (UINT32) (BaseAddress >> 12);
    ApicBaseMsr.Bits.ApicBaseHi = (UINT32) (RShiftU64((UINT64) BaseAddress, 32));
  
    AsmWriteMsr64 (MSR_IA32_APIC_BASE, ApicBaseMsr.Uint64);
  }
  
  /**
    Read from a local APIC register.
  
    This function reads from a local APIC register either in xAPIC or x2APIC mode.
    It is required that in xAPIC mode wider registers (64-bit or 256-bit) must be
    accessed using multiple 32-bit loads or stores, so this function only performs
    32-bit read.
  
    @param  MmioOffset  The MMIO offset of the local APIC register in xAPIC mode.
                        It must be 16-byte aligned.
  
    @return 32-bit      Value read from the register.
  **/
  UINT32
  EFIAPI
  ReadLocalApicReg (
    IN UINTN  MmioOffset
    )
  {
    UINT32 MsrIndex;
  
    ASSERT ((MmioOffset & 0xf) == 0);
  
    if (GetApicMode () == LOCAL_APIC_MODE_XAPIC) {
      return MmioRead32 (GetLocalApicBaseAddress() + MmioOffset);
    } else {
      //
      // DFR is not supported in x2APIC mode.
      //
      ASSERT (MmioOffset != XAPIC_ICR_DFR_OFFSET);
      //
      // Note that in x2APIC mode, ICR is a 64-bit MSR that needs special treatment. It
      // is not supported in this function for simplicity.
      //
      ASSERT (MmioOffset != XAPIC_ICR_HIGH_OFFSET);
  
      MsrIndex = (UINT32)(MmioOffset >> 4) + X2APIC_MSR_BASE_ADDRESS;
      return AsmReadMsr32 (MsrIndex);
    }
  }
  
  /**
    Write to a local APIC register.
  
    This function writes to a local APIC register either in xAPIC or x2APIC mode.
    It is required that in xAPIC mode wider registers (64-bit or 256-bit) must be
    accessed using multiple 32-bit loads or stores, so this function only performs
    32-bit write.
  
    if the register index is invalid or unsupported in current APIC mode, then ASSERT.
  
    @param  MmioOffset  The MMIO offset of the local APIC register in xAPIC mode.
                        It must be 16-byte aligned.
    @param  Value       Value to be written to the register.
  **/
  VOID
  EFIAPI
  WriteLocalApicReg (
    IN UINTN  MmioOffset,
    IN UINT32 Value
    )
  {
    UINT32 MsrIndex;
  
    ASSERT ((MmioOffset & 0xf) == 0);
  
    if (GetApicMode () == LOCAL_APIC_MODE_XAPIC) {
      MmioWrite32 (GetLocalApicBaseAddress() + MmioOffset, Value);
    } else {
      //
      // DFR is not supported in x2APIC mode.
      //
      ASSERT (MmioOffset != XAPIC_ICR_DFR_OFFSET);
      //
      // Note that in x2APIC mode, ICR is a 64-bit MSR that needs special treatment. It
      // is not supported in this function for simplicity.
      //
      ASSERT (MmioOffset != XAPIC_ICR_HIGH_OFFSET);
      ASSERT (MmioOffset != XAPIC_ICR_LOW_OFFSET);
  
      MsrIndex =  (UINT32)(MmioOffset >> 4) + X2APIC_MSR_BASE_ADDRESS;
      //
      // The serializing semantics of WRMSR are relaxed when writing to the APIC registers.
      // Use memory fence here to force the serializing semantics to be consisent with xAPIC mode.
      //
      MemoryFence ();
      AsmWriteMsr32 (MsrIndex, Value);
    }
  }
  
  /**
    Send an IPI by writing to ICR.
  
    This function returns after the IPI has been accepted by the target processor.
  
    @param  IcrLow 32-bit value to be written to the low half of ICR.
    @param  ApicId APIC ID of the target processor if this IPI is targeted for a specific processor.
  **/
  VOID
  SendIpi (
    IN UINT32          IcrLow,
    IN UINT32          ApicId
    )
  {
    UINT64             MsrValue;
    LOCAL_APIC_ICR_LOW IcrLowReg;
    UINTN              LocalApciBaseAddress;
    UINT32             IcrHigh;
    BOOLEAN            InterruptState;
  
    //
    // Legacy APIC or X2APIC?
    //
    if (GetApicMode () == LOCAL_APIC_MODE_XAPIC) {
      ASSERT (ApicId <= 0xff);
  
      InterruptState = SaveAndDisableInterrupts ();
  
      //
      // Get base address of this LAPIC
      //
      LocalApciBaseAddress = GetLocalApicBaseAddress();
  
      //
      // Save existing contents of ICR high 32 bits
      //
      IcrHigh = MmioRead32 (LocalApciBaseAddress + XAPIC_ICR_HIGH_OFFSET);
  
      //
      // Wait for DeliveryStatus clear in case a previous IPI
      //  is still being sent
      //
      do {
        IcrLowReg.Uint32 = MmioRead32 (LocalApciBaseAddress + XAPIC_ICR_LOW_OFFSET);
      } while (IcrLowReg.Bits.DeliveryStatus != 0);
  
      //
      // For xAPIC, the act of writing to the low doubleword of the ICR causes the IPI to be sent.
      //
      MmioWrite32 (LocalApciBaseAddress + XAPIC_ICR_HIGH_OFFSET, ApicId << 24);
      MmioWrite32 (LocalApciBaseAddress + XAPIC_ICR_LOW_OFFSET, IcrLow);
  
      //
      // Wait for DeliveryStatus clear again
      //
      do {
        IcrLowReg.Uint32 = MmioRead32 (LocalApciBaseAddress + XAPIC_ICR_LOW_OFFSET);
      } while (IcrLowReg.Bits.DeliveryStatus != 0);
  
      //
      // And restore old contents of ICR high
      //
      MmioWrite32 (LocalApciBaseAddress + XAPIC_ICR_HIGH_OFFSET, IcrHigh);
  
      SetInterruptState (InterruptState);
  
    } else {
      //
      // For x2APIC, A single MSR write to the Interrupt Command Register is required for dispatching an
      // interrupt in x2APIC mode.
      //
      MsrValue = LShiftU64 ((UINT64) ApicId, 32) | IcrLow;
      AsmWriteMsr64 (X2APIC_MSR_ICR_ADDRESS, MsrValue);
    }
  }
  
  //
  // Library API implementation functions
  //
  
  /**
    Get the current local APIC mode.
  
    If local APIC is disabled, then ASSERT.
  
    @retval LOCAL_APIC_MODE_XAPIC  current APIC mode is xAPIC.
    @retval LOCAL_APIC_MODE_X2APIC current APIC mode is x2APIC.
  **/
  UINTN
  EFIAPI
  GetApicMode (
    VOID
    )
  {
    MSR_IA32_APIC_BASE_REGISTER  ApicBaseMsr;
  
    if (!LocalApicBaseAddressMsrSupported ()) {
      //
      // If CPU does not support APIC Base Address MSR, then return XAPIC mode
      //
      return LOCAL_APIC_MODE_XAPIC;
    }
  
    ApicBaseMsr.Uint64 = AsmReadMsr64 (MSR_IA32_APIC_BASE);
    //
    // Local APIC should have been enabled
    //
    ASSERT (ApicBaseMsr.Bits.EN != 0);
    if (ApicBaseMsr.Bits.EXTD != 0) {
      return LOCAL_APIC_MODE_X2APIC;
    } else {
      return LOCAL_APIC_MODE_XAPIC;
    }
  }
  
  /**
    Set the current local APIC mode.
  
    If the specified local APIC mode is not valid, then ASSERT.
    If the specified local APIC mode can't be set as current, then ASSERT.
  
    @param ApicMode APIC mode to be set.
  
    @note  This API must not be called from an interrupt handler or SMI handler.
           It may result in unpredictable behavior.
  **/
  VOID
  EFIAPI
  SetApicMode (
    IN UINTN  ApicMode
    )
  {
    UINTN                        CurrentMode;
    MSR_IA32_APIC_BASE_REGISTER  ApicBaseMsr;
  
    if (!LocalApicBaseAddressMsrSupported ()) {
      //
      // Ignore set request if the CPU does not support APIC Base Address MSR
      //
      return;
    }
  
    CurrentMode = GetApicMode ();
    if (CurrentMode == LOCAL_APIC_MODE_XAPIC) {
      switch (ApicMode) {
        case LOCAL_APIC_MODE_XAPIC:
          break;
        case LOCAL_APIC_MODE_X2APIC:
          ApicBaseMsr.Uint64 = AsmReadMsr64 (MSR_IA32_APIC_BASE);
          ApicBaseMsr.Bits.EXTD = 1;
          AsmWriteMsr64 (MSR_IA32_APIC_BASE, ApicBaseMsr.Uint64);
          break;
        default:
          ASSERT (FALSE);
      }
    } else {
      switch (ApicMode) {
        case LOCAL_APIC_MODE_XAPIC:
          //
          //  Transition from x2APIC mode to xAPIC mode is a two-step process:
          //    x2APIC -> Local APIC disabled -> xAPIC
          //
          ApicBaseMsr.Uint64 = AsmReadMsr64 (MSR_IA32_APIC_BASE);
          ApicBaseMsr.Bits.EXTD = 0;
          ApicBaseMsr.Bits.EN = 0;
          AsmWriteMsr64 (MSR_IA32_APIC_BASE, ApicBaseMsr.Uint64);
          ApicBaseMsr.Bits.EN = 1;
          AsmWriteMsr64 (MSR_IA32_APIC_BASE, ApicBaseMsr.Uint64);
          break;
        case LOCAL_APIC_MODE_X2APIC:
          break;
        default:
          ASSERT (FALSE);
      }
    }
  }
  
  /**
    Get the initial local APIC ID of the executing processor assigned by hardware upon power on or reset.
  
    In xAPIC mode, the initial local APIC ID may be different from current APIC ID.
    In x2APIC mode, the local APIC ID can't be changed and there is no concept of initial APIC ID. In this case,
    the 32-bit local APIC ID is returned as initial APIC ID.
  
    @return  32-bit initial local APIC ID of the executing processor.
  **/
  UINT32
  EFIAPI
  GetInitialApicId (
    VOID
    )
  {
    UINT32 ApicId;
    UINT32 MaxCpuIdIndex;
    UINT32 RegEbx;
  
    if (GetApicMode () == LOCAL_APIC_MODE_XAPIC) {
      //
      // Get the max index of basic CPUID
      //
      AsmCpuid (CPUID_SIGNATURE, &MaxCpuIdIndex, NULL, NULL, NULL);
      //
      // If CPUID Leaf B is supported,
      // And CPUID.0BH:EBX[15:0] reports a non-zero value,
      // Then the initial 32-bit APIC ID = CPUID.0BH:EDX
      // Else the initial 8-bit APIC ID = CPUID.1:EBX[31:24]
      //
      if (MaxCpuIdIndex >= CPUID_EXTENDED_TOPOLOGY) {
        AsmCpuidEx (CPUID_EXTENDED_TOPOLOGY, 0, NULL, &RegEbx, NULL, &ApicId);
        if ((RegEbx & (BIT16 - 1)) != 0) {
          return ApicId;
        }
      }
      AsmCpuid (CPUID_VERSION_INFO, NULL, &RegEbx, NULL, NULL);
      return RegEbx >> 24;
    } else {
      return GetApicId ();
    }
  }
  
  /**
    Get the local APIC ID of the executing processor.
  
    @return  32-bit local APIC ID of the executing processor.
  **/
  UINT32
  EFIAPI
  GetApicId (
    VOID
    )
  {
    UINT32 ApicId;
    UINT32 InitApicId;
  
    ApicId = ReadLocalApicReg (XAPIC_ID_OFFSET);
    if (GetApicMode () == LOCAL_APIC_MODE_XAPIC) {
      ApicId = ((InitApicId = GetInitialApicId ()) < 0x100) ? (ApicId >> 24) : InitApicId;
    }
  
    return ApicId;
  }
  
  /**
    Get the value of the local APIC version register.
  
    @return  the value of the local APIC version register.
  **/
  UINT32
  EFIAPI
  GetApicVersion (
    VOID
    )
  {
    return ReadLocalApicReg (XAPIC_VERSION_OFFSET);
  }
  
  /**
    Send a Fixed IPI to a specified target processor.
  
    This function returns after the IPI has been accepted by the target processor.
  
    @param  ApicId   The local APIC ID of the target processor.
    @param  Vector   The vector number of the interrupt being sent.
  **/
  VOID
  EFIAPI
  SendFixedIpi (
    IN UINT32          ApicId,
    IN UINT8           Vector
    )
  {
    LOCAL_APIC_ICR_LOW IcrLow;
  
    IcrLow.Uint32 = 0;
    IcrLow.Bits.DeliveryMode = LOCAL_APIC_DELIVERY_MODE_FIXED;
    IcrLow.Bits.Level = 1;
    IcrLow.Bits.Vector = Vector;
    SendIpi (IcrLow.Uint32, ApicId);
  }
  
  /**
    Send a Fixed IPI to all processors excluding self.
  
    This function returns after the IPI has been accepted by the target processors.
  
    @param  Vector   The vector number of the interrupt being sent.
  **/
  VOID
  EFIAPI
  SendFixedIpiAllExcludingSelf (
    IN UINT8           Vector
    )
  {
    LOCAL_APIC_ICR_LOW IcrLow;
  
    IcrLow.Uint32 = 0;
    IcrLow.Bits.DeliveryMode = LOCAL_APIC_DELIVERY_MODE_FIXED;
    IcrLow.Bits.Level = 1;
    IcrLow.Bits.DestinationShorthand = LOCAL_APIC_DESTINATION_SHORTHAND_ALL_EXCLUDING_SELF;
    IcrLow.Bits.Vector = Vector;
    SendIpi (IcrLow.Uint32, 0);
  }
  
  /**
    Send a SMI IPI to a specified target processor.
  
    This function returns after the IPI has been accepted by the target processor.
  
    @param  ApicId   Specify the local APIC ID of the target processor.
  **/
  VOID
  EFIAPI
  SendSmiIpi (
    IN UINT32          ApicId
    )
  {
    LOCAL_APIC_ICR_LOW IcrLow;
  
    IcrLow.Uint32 = 0;
    IcrLow.Bits.DeliveryMode = LOCAL_APIC_DELIVERY_MODE_SMI;
    IcrLow.Bits.Level = 1;
    SendIpi (IcrLow.Uint32, ApicId);
  }
  
  /**
    Send a SMI IPI to all processors excluding self.
  
    This function returns after the IPI has been accepted by the target processors.
  **/
  VOID
  EFIAPI
  SendSmiIpiAllExcludingSelf (
    VOID
    )
  {
    LOCAL_APIC_ICR_LOW IcrLow;
  
    IcrLow.Uint32 = 0;
    IcrLow.Bits.DeliveryMode = LOCAL_APIC_DELIVERY_MODE_SMI;
    IcrLow.Bits.Level = 1;
    IcrLow.Bits.DestinationShorthand = LOCAL_APIC_DESTINATION_SHORTHAND_ALL_EXCLUDING_SELF;
    SendIpi (IcrLow.Uint32, 0);
  }
  
  /**
    Send an INIT IPI to a specified target processor.
  
    This function returns after the IPI has been accepted by the target processor.
  
    @param  ApicId   Specify the local APIC ID of the target processor.
  **/
  VOID
  EFIAPI
  SendInitIpi (
    IN UINT32          ApicId
    )
  {
    LOCAL_APIC_ICR_LOW IcrLow;
  
    IcrLow.Uint32 = 0;
    IcrLow.Bits.DeliveryMode = LOCAL_APIC_DELIVERY_MODE_INIT;
    IcrLow.Bits.Level = 1;
    SendIpi (IcrLow.Uint32, ApicId);
  }
  
  /**
    Send an INIT IPI to all processors excluding self.
  
    This function returns after the IPI has been accepted by the target processors.
  **/
  VOID
  EFIAPI
  SendInitIpiAllExcludingSelf (
    VOID
    )
  {
    LOCAL_APIC_ICR_LOW IcrLow;
  
    IcrLow.Uint32 = 0;
    IcrLow.Bits.DeliveryMode = LOCAL_APIC_DELIVERY_MODE_INIT;
    IcrLow.Bits.Level = 1;
    IcrLow.Bits.DestinationShorthand = LOCAL_APIC_DESTINATION_SHORTHAND_ALL_EXCLUDING_SELF;
    SendIpi (IcrLow.Uint32, 0);
  }
  
  /**
    Send an INIT-Start-up-Start-up IPI sequence to a specified target processor.
  
    This function returns after the IPI has been accepted by the target processor.
  
    if StartupRoutine >= 1M, then ASSERT.
    if StartupRoutine is not multiple of 4K, then ASSERT.
  
    @param  ApicId          Specify the local APIC ID of the target processor.
    @param  StartupRoutine  Points to a start-up routine which is below 1M physical
                            address and 4K aligned.
  **/
  VOID
  EFIAPI
  SendInitSipiSipi (
    IN UINT32          ApicId,
    IN UINT32          StartupRoutine
    )
  {
    LOCAL_APIC_ICR_LOW IcrLow;
  
    ASSERT (StartupRoutine < 0x100000);
    ASSERT ((StartupRoutine & 0xfff) == 0);
  
    SendInitIpi (ApicId);
    MicroSecondDelay (PcdGet32(PcdCpuInitIpiDelayInMicroSeconds));
    IcrLow.Uint32 = 0;
    IcrLow.Bits.Vector = (StartupRoutine >> 12);
    IcrLow.Bits.DeliveryMode = LOCAL_APIC_DELIVERY_MODE_STARTUP;
    IcrLow.Bits.Level = 1;
    SendIpi (IcrLow.Uint32, ApicId);
    if (!StandardSignatureIsAuthenticAMD ()) {
      MicroSecondDelay (200);
      SendIpi (IcrLow.Uint32, ApicId);
    }
  }
  
  /**
    Send an INIT-Start-up-Start-up IPI sequence to all processors excluding self.
  
    This function returns after the IPI has been accepted by the target processors.
  
    if StartupRoutine >= 1M, then ASSERT.
    if StartupRoutine is not multiple of 4K, then ASSERT.
  
    @param  StartupRoutine    Points to a start-up routine which is below 1M physical
                              address and 4K aligned.
  **/
  VOID
  EFIAPI
  SendInitSipiSipiAllExcludingSelf (
    IN UINT32          StartupRoutine
    )
  {
    LOCAL_APIC_ICR_LOW IcrLow;
  
    ASSERT (StartupRoutine < 0x100000);
    ASSERT ((StartupRoutine & 0xfff) == 0);
  
    SendInitIpiAllExcludingSelf ();
    MicroSecondDelay (PcdGet32(PcdCpuInitIpiDelayInMicroSeconds));
    IcrLow.Uint32 = 0;
    IcrLow.Bits.Vector = (StartupRoutine >> 12);
    IcrLow.Bits.DeliveryMode = LOCAL_APIC_DELIVERY_MODE_STARTUP;
    IcrLow.Bits.Level = 1;
    IcrLow.Bits.DestinationShorthand = LOCAL_APIC_DESTINATION_SHORTHAND_ALL_EXCLUDING_SELF;
    SendIpi (IcrLow.Uint32, 0);
    if (!StandardSignatureIsAuthenticAMD ()) {
      MicroSecondDelay (200);
      SendIpi (IcrLow.Uint32, 0);
    }
  }
  
  /**
    Initialize the state of the SoftwareEnable bit in the Local APIC
    Spurious Interrupt Vector register.
  
    @param  Enable  If TRUE, then set SoftwareEnable to 1
                    If FALSE, then set SoftwareEnable to 0.
  
  **/
  VOID
  EFIAPI
  InitializeLocalApicSoftwareEnable (
    IN BOOLEAN  Enable
    )
  {
    LOCAL_APIC_SVR  Svr;
  
    //
    // Set local APIC software-enabled bit.
    //
    Svr.Uint32 = ReadLocalApicReg (XAPIC_SPURIOUS_VECTOR_OFFSET);
    if (Enable) {
      if (Svr.Bits.SoftwareEnable == 0) {
        Svr.Bits.SoftwareEnable = 1;
        WriteLocalApicReg (XAPIC_SPURIOUS_VECTOR_OFFSET, Svr.Uint32);
      }
    } else {
      if (Svr.Bits.SoftwareEnable == 1) {
        Svr.Bits.SoftwareEnable = 0;
        WriteLocalApicReg (XAPIC_SPURIOUS_VECTOR_OFFSET, Svr.Uint32);
      }
    }
  }
  
  /**
    Programming Virtual Wire Mode.
  
    This function programs the local APIC for virtual wire mode following
    the example described in chapter A.3 of the MP 1.4 spec.
  
    IOxAPIC is not involved in this type of virtual wire mode.
  **/
  VOID
  EFIAPI
  ProgramVirtualWireMode (
    VOID
    )
  {
    LOCAL_APIC_SVR      Svr;
    LOCAL_APIC_LVT_LINT Lint;
  
    //
    // Enable the APIC via SVR and set the spurious interrupt to use Int 00F.
    //
    Svr.Uint32 = ReadLocalApicReg (XAPIC_SPURIOUS_VECTOR_OFFSET);
    Svr.Bits.SpuriousVector = 0xf;
    Svr.Bits.SoftwareEnable = 1;
    WriteLocalApicReg (XAPIC_SPURIOUS_VECTOR_OFFSET, Svr.Uint32);
  
    //
    // Program the LINT0 vector entry as ExtInt. Not masked, edge, active high.
    //
    Lint.Uint32 = ReadLocalApicReg (XAPIC_LVT_LINT0_OFFSET);
    Lint.Bits.DeliveryMode = LOCAL_APIC_DELIVERY_MODE_EXTINT;
    Lint.Bits.InputPinPolarity = 0;
    Lint.Bits.TriggerMode = 0;
    Lint.Bits.Mask = 0;
    WriteLocalApicReg (XAPIC_LVT_LINT0_OFFSET, Lint.Uint32);
  
    //
    // Program the LINT0 vector entry as NMI. Not masked, edge, active high.
    //
    Lint.Uint32 = ReadLocalApicReg (XAPIC_LVT_LINT1_OFFSET);
    Lint.Bits.DeliveryMode = LOCAL_APIC_DELIVERY_MODE_NMI;
    Lint.Bits.InputPinPolarity = 0;
    Lint.Bits.TriggerMode = 0;
    Lint.Bits.Mask = 0;
    WriteLocalApicReg (XAPIC_LVT_LINT1_OFFSET, Lint.Uint32);
  }
  
  /**
    Disable LINT0 & LINT1 interrupts.
  
    This function sets the mask flag in the LVT LINT0 & LINT1 registers.
  **/
  VOID
  EFIAPI
  DisableLvtInterrupts (
    VOID
    )
  {
    LOCAL_APIC_LVT_LINT LvtLint;
  
    LvtLint.Uint32 = ReadLocalApicReg (XAPIC_LVT_LINT0_OFFSET);
    LvtLint.Bits.Mask = 1;
    WriteLocalApicReg (XAPIC_LVT_LINT0_OFFSET, LvtLint.Uint32);
  
    LvtLint.Uint32 = ReadLocalApicReg (XAPIC_LVT_LINT1_OFFSET);
    LvtLint.Bits.Mask = 1;
    WriteLocalApicReg (XAPIC_LVT_LINT1_OFFSET, LvtLint.Uint32);
  }
  
  /**
    Read the initial count value from the init-count register.
  
    @return The initial count value read from the init-count register.
  **/
  UINT32
  EFIAPI
  GetApicTimerInitCount (
    VOID
    )
  {
    return ReadLocalApicReg (XAPIC_TIMER_INIT_COUNT_OFFSET);
  }
  
  /**
    Read the current count value from the current-count register.
  
    @return The current count value read from the current-count register.
  **/
  UINT32
  EFIAPI
  GetApicTimerCurrentCount (
    VOID
    )
  {
    return ReadLocalApicReg (XAPIC_TIMER_CURRENT_COUNT_OFFSET);
  }
  
  /**
    Initialize the local APIC timer.
  
    The local APIC timer is initialized and enabled.
  
    @param DivideValue   The divide value for the DCR. It is one of 1,2,4,8,16,32,64,128.
                         If it is 0, then use the current divide value in the DCR.
    @param InitCount     The initial count value.
    @param PeriodicMode  If TRUE, timer mode is peridoic. Othewise, timer mode is one-shot.
    @param Vector        The timer interrupt vector number.
  **/
  VOID
  EFIAPI
  InitializeApicTimer (
    IN UINTN   DivideValue,
    IN UINT32  InitCount,
    IN BOOLEAN PeriodicMode,
    IN UINT8   Vector
    )
  {
    LOCAL_APIC_DCR       Dcr;
    LOCAL_APIC_LVT_TIMER LvtTimer;
    UINT32               Divisor;
  
    //
    // Ensure local APIC is in software-enabled state.
    //
    InitializeLocalApicSoftwareEnable (TRUE);
  
    //
    // Program init-count register.
    //
    WriteLocalApicReg (XAPIC_TIMER_INIT_COUNT_OFFSET, InitCount);
  
    if (DivideValue != 0) {
      ASSERT (DivideValue <= 128);
      ASSERT (DivideValue == GetPowerOfTwo32((UINT32)DivideValue));
      Divisor = (UINT32)((HighBitSet32 ((UINT32)DivideValue) - 1) & 0x7);
  
      Dcr.Uint32 = ReadLocalApicReg (XAPIC_TIMER_DIVIDE_CONFIGURATION_OFFSET);
      Dcr.Bits.DivideValue1 = (Divisor & 0x3);
      Dcr.Bits.DivideValue2 = (Divisor >> 2);
      WriteLocalApicReg (XAPIC_TIMER_DIVIDE_CONFIGURATION_OFFSET, Dcr.Uint32);
    }
  
    //
    // Enable APIC timer interrupt with specified timer mode.
    //
    LvtTimer.Uint32 = ReadLocalApicReg (XAPIC_LVT_TIMER_OFFSET);
    if (PeriodicMode) {
      LvtTimer.Bits.TimerMode = 1;
    } else {
      LvtTimer.Bits.TimerMode = 0;
    }
    LvtTimer.Bits.Mask = 0;
    LvtTimer.Bits.Vector = Vector;
    WriteLocalApicReg (XAPIC_LVT_TIMER_OFFSET, LvtTimer.Uint32);
  }
  
  /**
    Get the state of the local APIC timer.
  
    This function will ASSERT if the local APIC is not software enabled.
  
    @param DivideValue   Return the divide value for the DCR. It is one of 1,2,4,8,16,32,64,128.
    @param PeriodicMode  Return the timer mode. If TRUE, timer mode is peridoic. Othewise, timer mode is one-shot.
    @param Vector        Return the timer interrupt vector number.
  **/
  VOID
  EFIAPI
  GetApicTimerState (
    OUT UINTN    *DivideValue  OPTIONAL,
    OUT BOOLEAN  *PeriodicMode  OPTIONAL,
    OUT UINT8    *Vector  OPTIONAL
    )
  {
    UINT32 Divisor;
    LOCAL_APIC_DCR Dcr;
    LOCAL_APIC_LVT_TIMER LvtTimer;
  
    //
    // Check the APIC Software Enable/Disable bit (bit 8) in Spurious-Interrupt
    // Vector Register.
    // This bit will be 1, if local APIC is software enabled.
    //
    ASSERT ((ReadLocalApicReg(XAPIC_SPURIOUS_VECTOR_OFFSET) & BIT8) != 0);
  
    if (DivideValue != NULL) {
      Dcr.Uint32 = ReadLocalApicReg (XAPIC_TIMER_DIVIDE_CONFIGURATION_OFFSET);
      Divisor = Dcr.Bits.DivideValue1 | (Dcr.Bits.DivideValue2 << 2);
      Divisor = (Divisor + 1) & 0x7;
      *DivideValue = ((UINTN)1) << Divisor;
    }
  
    if (PeriodicMode != NULL || Vector != NULL) {
      LvtTimer.Uint32 = ReadLocalApicReg (XAPIC_LVT_TIMER_OFFSET);
      if (PeriodicMode != NULL) {
        if (LvtTimer.Bits.TimerMode == 1) {
          *PeriodicMode = TRUE;
        } else {
          *PeriodicMode = FALSE;
        }
      }
      if (Vector != NULL) {
        *Vector = (UINT8) LvtTimer.Bits.Vector;
      }
    }
  }
  
  /**
    Enable the local APIC timer interrupt.
  **/
  VOID
  EFIAPI
  EnableApicTimerInterrupt (
    VOID
    )
  {
    LOCAL_APIC_LVT_TIMER LvtTimer;
  
    LvtTimer.Uint32 = ReadLocalApicReg (XAPIC_LVT_TIMER_OFFSET);
    LvtTimer.Bits.Mask = 0;
    WriteLocalApicReg (XAPIC_LVT_TIMER_OFFSET, LvtTimer.Uint32);
  }
  
  /**
    Disable the local APIC timer interrupt.
  **/
  VOID
  EFIAPI
  DisableApicTimerInterrupt (
    VOID
    )
  {
    LOCAL_APIC_LVT_TIMER LvtTimer;
  
    LvtTimer.Uint32 = ReadLocalApicReg (XAPIC_LVT_TIMER_OFFSET);
    LvtTimer.Bits.Mask = 1;
    WriteLocalApicReg (XAPIC_LVT_TIMER_OFFSET, LvtTimer.Uint32);
  }
  
  /**
    Get the local APIC timer interrupt state.
  
    @retval TRUE  The local APIC timer interrupt is enabled.
    @retval FALSE The local APIC timer interrupt is disabled.
  **/
  BOOLEAN
  EFIAPI
  GetApicTimerInterruptState (
    VOID
    )
  {
    LOCAL_APIC_LVT_TIMER LvtTimer;
  
    LvtTimer.Uint32 = ReadLocalApicReg (XAPIC_LVT_TIMER_OFFSET);
    return (BOOLEAN)(LvtTimer.Bits.Mask == 0);
  }
  
  /**
    Send EOI to the local APIC.
  **/
  VOID
  EFIAPI
  SendApicEoi (
    VOID
    )
  {
    WriteLocalApicReg (XAPIC_EOI_OFFSET, 0);
  }
  
  /**
    Get the 32-bit address that a device should use to send a Message Signaled
    Interrupt (MSI) to the Local APIC of the currently executing processor.
  
    @return 32-bit address used to send an MSI to the Local APIC.
  **/
  UINT32
  EFIAPI
  GetApicMsiAddress (
    VOID
    )
  {
    LOCAL_APIC_MSI_ADDRESS  MsiAddress;
  
    //
    // Return address for an MSI interrupt to be delivered only to the APIC ID
    // of the currently executing processor.
    //
    MsiAddress.Uint32             = 0;
    MsiAddress.Bits.BaseAddress   = 0xFEE;
    MsiAddress.Bits.DestinationId = GetApicId ();
    return MsiAddress.Uint32;
  }
  
  /**
    Get the 64-bit data value that a device should use to send a Message Signaled
    Interrupt (MSI) to the Local APIC of the currently executing processor.
  
    If Vector is not in range 0x10..0xFE, then ASSERT().
    If DeliveryMode is not supported, then ASSERT().
  
    @param  Vector          The 8-bit interrupt vector associated with the MSI.
                            Must be in the range 0x10..0xFE
    @param  DeliveryMode    A 3-bit value that specifies how the recept of the MSI
                            is handled.  The only supported values are:
                              0: LOCAL_APIC_DELIVERY_MODE_FIXED
                              1: LOCAL_APIC_DELIVERY_MODE_LOWEST_PRIORITY
                              2: LOCAL_APIC_DELIVERY_MODE_SMI
                              4: LOCAL_APIC_DELIVERY_MODE_NMI
                              5: LOCAL_APIC_DELIVERY_MODE_INIT
                              7: LOCAL_APIC_DELIVERY_MODE_EXTINT
  
    @param  LevelTriggered  TRUE specifies a level triggered interrupt.
                            FALSE specifies an edge triggered interrupt.
    @param  AssertionLevel  Ignored if LevelTriggered is FALSE.
                            TRUE specifies a level triggered interrupt that active
                            when the interrupt line is asserted.
                            FALSE specifies a level triggered interrupt that active
                            when the interrupt line is deasserted.
  
    @return 64-bit data value used to send an MSI to the Local APIC.
  **/
  UINT64
  EFIAPI
  GetApicMsiValue (
    IN UINT8    Vector,
    IN UINTN    DeliveryMode,
    IN BOOLEAN  LevelTriggered,
    IN BOOLEAN  AssertionLevel
    )
  {
    LOCAL_APIC_MSI_DATA  MsiData;
  
    ASSERT (Vector >= 0x10 && Vector <= 0xFE);
    ASSERT (DeliveryMode < 8 && DeliveryMode != 6 && DeliveryMode != 3);
  
    MsiData.Uint64            = 0;
    MsiData.Bits.Vector       = Vector;
    MsiData.Bits.DeliveryMode = (UINT32)DeliveryMode;
    if (LevelTriggered) {
      MsiData.Bits.TriggerMode = 1;
      if (AssertionLevel) {
        MsiData.Bits.Level = 1;
      }
    }
    return MsiData.Uint64;
  }
  
  /**
    Get Package ID/Core ID/Thread ID of a processor.
  
    The algorithm assumes the target system has symmetry across physical
    package  boundaries with respect to the number of logical processors
    per package,  number of cores per package.
  
    @param[in]  InitialApicId  Initial APIC ID of the target logical processor.
    @param[out]  Package       Returns the processor package ID.
    @param[out]  Core          Returns the processor core ID.
    @param[out]  Thread        Returns the processor thread ID.
  **/
  VOID
  EFIAPI
  GetProcessorLocationByApicId (
    IN  UINT32  InitialApicId,
    OUT UINT32  *Package  OPTIONAL,
    OUT UINT32  *Core    OPTIONAL,
    OUT UINT32  *Thread  OPTIONAL
    )
  {
    BOOLEAN                             TopologyLeafSupported;
    CPUID_VERSION_INFO_EBX              VersionInfoEbx;
    CPUID_VERSION_INFO_EDX              VersionInfoEdx;
    CPUID_CACHE_PARAMS_EAX              CacheParamsEax;
    CPUID_EXTENDED_TOPOLOGY_EAX         ExtendedTopologyEax;
    CPUID_EXTENDED_TOPOLOGY_EBX         ExtendedTopologyEbx;
    CPUID_EXTENDED_TOPOLOGY_ECX         ExtendedTopologyEcx;
    CPUID_AMD_EXTENDED_CPU_SIG_ECX      AmdExtendedCpuSigEcx;
    CPUID_AMD_PROCESSOR_TOPOLOGY_EBX    AmdProcessorTopologyEbx;
    CPUID_AMD_VIR_PHY_ADDRESS_SIZE_ECX  AmdVirPhyAddressSizeEcx;
    UINT32                              MaxStandardCpuIdIndex;
    UINT32                              MaxExtendedCpuIdIndex;
    UINT32                              SubIndex;
    UINTN                               LevelType;
    UINT32                              MaxLogicProcessorsPerPackage;
    UINT32                              MaxCoresPerPackage;
    UINTN                               ThreadBits;
    UINTN                               CoreBits;
  
    //
    // Check if the processor is capable of supporting more than one logical processor.
    //
    AsmCpuid (CPUID_VERSION_INFO, NULL, NULL, NULL, &VersionInfoEdx.Uint32);
    if (VersionInfoEdx.Bits.HTT == 0) {
      if (Thread != NULL) {
        *Thread = 0;
      }
      if (Core != NULL) {
        *Core = 0;
      }
      if (Package != NULL) {
        *Package = 0;
      }
      return;
    }
  
    //
    // Assume three-level mapping of APIC ID: Package|Core|Thread.
    //
    ThreadBits = 0;
    CoreBits = 0;
  
    //
    // Get max index of CPUID
    //
    AsmCpuid (CPUID_SIGNATURE, &MaxStandardCpuIdIndex, NULL, NULL, NULL);
    AsmCpuid (CPUID_EXTENDED_FUNCTION, &MaxExtendedCpuIdIndex, NULL, NULL, NULL);
  
    //
    // If the extended topology enumeration leaf is available, it
    // is the preferred mechanism for enumerating topology.
    //
    TopologyLeafSupported = FALSE;
    if (MaxStandardCpuIdIndex >= CPUID_EXTENDED_TOPOLOGY) {
      AsmCpuidEx(
        CPUID_EXTENDED_TOPOLOGY,
        0,
        &ExtendedTopologyEax.Uint32,
        &ExtendedTopologyEbx.Uint32,
        &ExtendedTopologyEcx.Uint32,
        NULL
        );
      //
      // If CPUID.(EAX=0BH, ECX=0H):EBX returns zero and maximum input value for
      // basic CPUID information is greater than 0BH, then CPUID.0BH leaf is not
      // supported on that processor.
      //
      if (ExtendedTopologyEbx.Uint32 != 0) {
        TopologyLeafSupported = TRUE;
  
        //
        // Sub-leaf index 0 (ECX= 0 as input) provides enumeration parameters to extract
        // the SMT sub-field of x2APIC ID.
        //
        LevelType = ExtendedTopologyEcx.Bits.LevelType;
        ASSERT (LevelType == CPUID_EXTENDED_TOPOLOGY_LEVEL_TYPE_SMT);
        ThreadBits = ExtendedTopologyEax.Bits.ApicIdShift;
  
        //
        // Software must not assume any "level type" encoding
        // value to be related to any sub-leaf index, except sub-leaf 0.
        //
        SubIndex = 1;
        do {
          AsmCpuidEx (
            CPUID_EXTENDED_TOPOLOGY,
            SubIndex,
            &ExtendedTopologyEax.Uint32,
            NULL,
            &ExtendedTopologyEcx.Uint32,
            NULL
            );
          LevelType = ExtendedTopologyEcx.Bits.LevelType;
          if (LevelType == CPUID_EXTENDED_TOPOLOGY_LEVEL_TYPE_CORE) {
            CoreBits = ExtendedTopologyEax.Bits.ApicIdShift - ThreadBits;
            break;
          }
          SubIndex++;
        } while (LevelType != CPUID_EXTENDED_TOPOLOGY_LEVEL_TYPE_INVALID);
      }
    }
  
    if (!TopologyLeafSupported) {
      //
      // Get logical processor count
      //
      AsmCpuid (CPUID_VERSION_INFO, NULL, &VersionInfoEbx.Uint32, NULL, NULL);
      MaxLogicProcessorsPerPackage = VersionInfoEbx.Bits.MaximumAddressableIdsForLogicalProcessors;
  
      //
      // Assume single-core processor
      //
      MaxCoresPerPackage = 1;
  
      //
      // Check for topology extensions on AMD processor
      //
      if (StandardSignatureIsAuthenticAMD()) {
        if (MaxExtendedCpuIdIndex >= CPUID_AMD_PROCESSOR_TOPOLOGY) {
          AsmCpuid (CPUID_EXTENDED_CPU_SIG, NULL, NULL, &AmdExtendedCpuSigEcx.Uint32, NULL);
          if (AmdExtendedCpuSigEcx.Bits.TopologyExtensions != 0) {
            //
            // Account for max possible thread count to decode ApicId
            //
            AsmCpuid (CPUID_VIR_PHY_ADDRESS_SIZE, NULL, NULL, &AmdVirPhyAddressSizeEcx.Uint32, NULL);
            MaxLogicProcessorsPerPackage = 1 << AmdVirPhyAddressSizeEcx.Bits.ApicIdCoreIdSize;
  
            //
            // Get cores per processor package
            //
            AsmCpuid (CPUID_AMD_PROCESSOR_TOPOLOGY, NULL, &AmdProcessorTopologyEbx.Uint32, NULL, NULL);
            MaxCoresPerPackage = MaxLogicProcessorsPerPackage / (AmdProcessorTopologyEbx.Bits.ThreadsPerCore + 1);
          }
        }
      }
      else {
        //
        // Extract core count based on CACHE information
        //
        if (MaxStandardCpuIdIndex >= CPUID_CACHE_PARAMS) {
          AsmCpuidEx (CPUID_CACHE_PARAMS, 0, &CacheParamsEax.Uint32, NULL, NULL, NULL);
          if (CacheParamsEax.Uint32 != 0) {
            MaxCoresPerPackage = CacheParamsEax.Bits.MaximumAddressableIdsForLogicalProcessors + 1;
          }
        }
      }
  
      ThreadBits = (UINTN)(HighBitSet32(MaxLogicProcessorsPerPackage / MaxCoresPerPackage - 1) + 1);
      CoreBits = (UINTN)(HighBitSet32(MaxCoresPerPackage - 1) + 1);
    }
  
    if (Thread != NULL) {
      *Thread = InitialApicId & ((1 << ThreadBits) - 1);
    }
    if (Core != NULL) {
      *Core = (InitialApicId >> ThreadBits) & ((1 << CoreBits) - 1);
    }
    if (Package != NULL) {
      *Package = (InitialApicId >> (ThreadBits + CoreBits));
    }
  }
  
  /**
    Get Package ID/Die ID/Tile ID/Module ID/Core ID/Thread ID of a processor.
  
    The algorithm assumes the target system has symmetry across physical
    package boundaries with respect to the number of threads per core, number of
    cores per module, number of modules per tile, number of tiles per die, number
    of dies per package.
  
    @param[in]   InitialApicId Initial APIC ID of the target logical processor.
    @param[out]  Package       Returns the processor package ID.
    @param[out]  Die           Returns the processor die ID.
    @param[out]  Tile          Returns the processor tile ID.
    @param[out]  Module        Returns the processor module ID.
    @param[out]  Core          Returns the processor core ID.
    @param[out]  Thread        Returns the processor thread ID.
  **/
  VOID
  EFIAPI
  GetProcessorLocation2ByApicId (
    IN  UINT32  InitialApicId,
    OUT UINT32  *Package  OPTIONAL,
    OUT UINT32  *Die      OPTIONAL,
    OUT UINT32  *Tile     OPTIONAL,
    OUT UINT32  *Module   OPTIONAL,
    OUT UINT32  *Core     OPTIONAL,
    OUT UINT32  *Thread   OPTIONAL
    )
  {
    CPUID_EXTENDED_TOPOLOGY_EAX         ExtendedTopologyEax;
    CPUID_EXTENDED_TOPOLOGY_ECX         ExtendedTopologyEcx;
    UINT32                              MaxStandardCpuIdIndex;
    UINT32                              Index;
    UINTN                               LevelType;
    UINT32                              Bits[CPUID_V2_EXTENDED_TOPOLOGY_LEVEL_TYPE_DIE + 2];
    UINT32                              *Location[CPUID_V2_EXTENDED_TOPOLOGY_LEVEL_TYPE_DIE + 2];
  
    for (LevelType = 0; LevelType < ARRAY_SIZE (Bits); LevelType++) {
      Bits[LevelType] = 0;
    }
  
    //
    // Get max index of CPUID
    //
    AsmCpuid (CPUID_SIGNATURE, &MaxStandardCpuIdIndex, NULL, NULL, NULL);
    if (MaxStandardCpuIdIndex < CPUID_V2_EXTENDED_TOPOLOGY) {
      if (Die != NULL) {
        *Die = 0;
      }
      if (Tile != NULL) {
        *Tile = 0;
      }
      if (Module != NULL) {
        *Module = 0;
      }
      GetProcessorLocationByApicId (InitialApicId, Package, Core, Thread);
      return;
    }
  
    //
    // If the V2 extended topology enumeration leaf is available, it
    // is the preferred mechanism for enumerating topology.
    //
    for (Index = 0; ; Index++) {
      AsmCpuidEx(
        CPUID_V2_EXTENDED_TOPOLOGY,
        Index,
        &ExtendedTopologyEax.Uint32,
        NULL,
        &ExtendedTopologyEcx.Uint32,
        NULL
        );
  
      LevelType = ExtendedTopologyEcx.Bits.LevelType;
  
      //
      // first level reported should be SMT.
      //
      ASSERT ((Index != 0) || (LevelType == CPUID_EXTENDED_TOPOLOGY_LEVEL_TYPE_SMT));
      if (LevelType == CPUID_EXTENDED_TOPOLOGY_LEVEL_TYPE_INVALID) {
        break;
      }
      ASSERT (LevelType < ARRAY_SIZE (Bits));
      Bits[LevelType] = ExtendedTopologyEax.Bits.ApicIdShift;
    }
  
    for (LevelType = CPUID_EXTENDED_TOPOLOGY_LEVEL_TYPE_CORE; LevelType < ARRAY_SIZE (Bits); LevelType++) {
      //
      // If there are more levels between level-1 (low-level) and level-2 (high-level), the unknown levels will be ignored
      // and treated as an extension of the last known level (i.e., level-1 in this case).
      //
      if (Bits[LevelType] == 0) {
        Bits[LevelType] = Bits[LevelType - 1];
      }
    }
  
    Location[CPUID_V2_EXTENDED_TOPOLOGY_LEVEL_TYPE_DIE + 1] = Package;
    Location[CPUID_V2_EXTENDED_TOPOLOGY_LEVEL_TYPE_DIE    ] = Die;
    Location[CPUID_V2_EXTENDED_TOPOLOGY_LEVEL_TYPE_TILE   ] = Tile;
    Location[CPUID_V2_EXTENDED_TOPOLOGY_LEVEL_TYPE_MODULE ] = Module;
    Location[CPUID_EXTENDED_TOPOLOGY_LEVEL_TYPE_CORE   ]    = Core;
    Location[CPUID_EXTENDED_TOPOLOGY_LEVEL_TYPE_SMT    ]    = Thread;
  
    Bits[CPUID_V2_EXTENDED_TOPOLOGY_LEVEL_TYPE_DIE + 1] = 32;
  
    for ( LevelType = CPUID_EXTENDED_TOPOLOGY_LEVEL_TYPE_SMT
        ; LevelType <= CPUID_V2_EXTENDED_TOPOLOGY_LEVEL_TYPE_DIE + 1
        ; LevelType ++
        ) {
      if (Location[LevelType] != NULL) {
        //
        // Bits[i] holds the number of bits to shift right on x2APIC ID to get a unique
        // topology ID of the next level type.
        //
        *Location[LevelType] = InitialApicId >> Bits[LevelType - 1];
  
        //
        // Bits[i] - Bits[i-1] holds the number of bits for the next ONE level type.
        //
        *Location[LevelType] &= (1 << (Bits[LevelType] - Bits[LevelType - 1])) - 1;
      }
    }
  }
  