/**@file
  Memory Detection for Virtual Machines.

  Copyright (c) 2006 - 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.

Module Name:

  MemDetect.c

**/

//
// The package level header files this module uses
//
#include <IndustryStandard/E820.h>
#include <IndustryStandard/Q35MchIch9.h>
#include <PiPei.h>

//
// The Library classes this module consumes
//
#include <Library/BaseLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/HobLib.h>
#include <Library/IoLib.h>
#include <Library/PcdLib.h>
#include <Library/PciLib.h>
#include <Library/PeimEntryPoint.h>
#include <Library/ResourcePublicationLib.h>
#include <Library/MtrrLib.h>
#include <Library/QemuFwCfgLib.h>

#include "Platform.h"
#include "Cmos.h"

UINT8 mPhysMemAddressWidth;

STATIC UINT32 mS3AcpiReservedMemoryBase;
STATIC UINT32 mS3AcpiReservedMemorySize;

STATIC UINT16 mQ35TsegMbytes;

VOID
Q35TsegMbytesInitialization (
  VOID
  )
{
  UINT16        ExtendedTsegMbytes;
  RETURN_STATUS PcdStatus;

  if (mHostBridgeDevId != INTEL_Q35_MCH_DEVICE_ID) {
    DEBUG ((
      DEBUG_ERROR,
      "%a: no TSEG (SMRAM) on host bridge DID=0x%04x; "
      "only DID=0x%04x (Q35) is supported\n",
      __FUNCTION__,
      mHostBridgeDevId,
      INTEL_Q35_MCH_DEVICE_ID
      ));
    ASSERT (FALSE);
    CpuDeadLoop ();
  }

  //
  // Check if QEMU offers an extended TSEG.
  //
  // This can be seen from writing MCH_EXT_TSEG_MB_QUERY to the MCH_EXT_TSEG_MB
  // register, and reading back the register.
  //
  // On a QEMU machine type that does not offer an extended TSEG, the initial
  // write overwrites whatever value a malicious guest OS may have placed in
  // the (unimplemented) register, before entering S3 or rebooting.
  // Subsequently, the read returns MCH_EXT_TSEG_MB_QUERY unchanged.
  //
  // On a QEMU machine type that offers an extended TSEG, the initial write
  // triggers an update to the register. Subsequently, the value read back
  // (which is guaranteed to differ from MCH_EXT_TSEG_MB_QUERY) tells us the
  // number of megabytes.
  //
  PciWrite16 (DRAMC_REGISTER_Q35 (MCH_EXT_TSEG_MB), MCH_EXT_TSEG_MB_QUERY);
  ExtendedTsegMbytes = PciRead16 (DRAMC_REGISTER_Q35 (MCH_EXT_TSEG_MB));
  if (ExtendedTsegMbytes == MCH_EXT_TSEG_MB_QUERY) {
    mQ35TsegMbytes = PcdGet16 (PcdQ35TsegMbytes);
    return;
  }

  DEBUG ((
    DEBUG_INFO,
    "%a: QEMU offers an extended TSEG (%d MB)\n",
    __FUNCTION__,
    ExtendedTsegMbytes
    ));
  PcdStatus = PcdSet16S (PcdQ35TsegMbytes, ExtendedTsegMbytes);
  ASSERT_RETURN_ERROR (PcdStatus);
  mQ35TsegMbytes = ExtendedTsegMbytes;
}


/**
  Iterate over the RAM entries in QEMU's fw_cfg E820 RAM map that start outside
  of the 32-bit address range.

  Find the highest exclusive >=4GB RAM address, or produce memory resource
  descriptor HOBs for RAM entries that start at or above 4GB.

  @param[out] MaxAddress  If MaxAddress is NULL, then ScanOrAdd64BitE820Ram()
                          produces memory resource descriptor HOBs for RAM
                          entries that start at or above 4GB.

                          Otherwise, MaxAddress holds the highest exclusive
                          >=4GB RAM address on output. If QEMU's fw_cfg E820
                          RAM map contains no RAM entry that starts outside of
                          the 32-bit address range, then MaxAddress is exactly
                          4GB on output.

  @retval EFI_SUCCESS         The fw_cfg E820 RAM map was found and processed.

  @retval EFI_PROTOCOL_ERROR  The RAM map was found, but its size wasn't a
                              whole multiple of sizeof(EFI_E820_ENTRY64). No
                              RAM entry was processed.

  @return                     Error codes from QemuFwCfgFindFile(). No RAM
                              entry was processed.
**/
STATIC
EFI_STATUS
ScanOrAdd64BitE820Ram (
  OUT UINT64 *MaxAddress OPTIONAL
  )
{
  EFI_STATUS           Status;
  FIRMWARE_CONFIG_ITEM FwCfgItem;
  UINTN                FwCfgSize;
  EFI_E820_ENTRY64     E820Entry;
  UINTN                Processed;

  Status = QemuFwCfgFindFile ("etc/e820", &FwCfgItem, &FwCfgSize);
  if (EFI_ERROR (Status)) {
    return Status;
  }
  if (FwCfgSize % sizeof E820Entry != 0) {
    return EFI_PROTOCOL_ERROR;
  }

  if (MaxAddress != NULL) {
    *MaxAddress = BASE_4GB;
  }

  QemuFwCfgSelectItem (FwCfgItem);
  for (Processed = 0; Processed < FwCfgSize; Processed += sizeof E820Entry) {
    QemuFwCfgReadBytes (sizeof E820Entry, &E820Entry);
    DEBUG ((
      DEBUG_VERBOSE,
      "%a: Base=0x%Lx Length=0x%Lx Type=%u\n",
      __FUNCTION__,
      E820Entry.BaseAddr,
      E820Entry.Length,
      E820Entry.Type
      ));
    if (E820Entry.Type == EfiAcpiAddressRangeMemory &&
        E820Entry.BaseAddr >= BASE_4GB) {
      if (MaxAddress == NULL) {
        UINT64 Base;
        UINT64 End;

        //
        // Round up the start address, and round down the end address.
        //
        Base = ALIGN_VALUE (E820Entry.BaseAddr, (UINT64)EFI_PAGE_SIZE);
        End = (E820Entry.BaseAddr + E820Entry.Length) &
              ~(UINT64)EFI_PAGE_MASK;
        if (Base < End) {
          AddMemoryRangeHob (Base, End);
          DEBUG ((
            DEBUG_VERBOSE,
            "%a: AddMemoryRangeHob [0x%Lx, 0x%Lx)\n",
            __FUNCTION__,
            Base,
            End
            ));
        }
      } else {
        UINT64 Candidate;

        Candidate = E820Entry.BaseAddr + E820Entry.Length;
        if (Candidate > *MaxAddress) {
          *MaxAddress = Candidate;
          DEBUG ((
            DEBUG_VERBOSE,
            "%a: MaxAddress=0x%Lx\n",
            __FUNCTION__,
            *MaxAddress
            ));
        }
      }
    }
  }
  return EFI_SUCCESS;
}


UINT32
GetSystemMemorySizeBelow4gb (
  VOID
  )
{
  UINT8 Cmos0x34;
  UINT8 Cmos0x35;

  //
  // CMOS 0x34/0x35 specifies the system memory above 16 MB.
  // * CMOS(0x35) is the high byte
  // * CMOS(0x34) is the low byte
  // * The size is specified in 64kb chunks
  // * Since this is memory above 16MB, the 16MB must be added
  //   into the calculation to get the total memory size.
  //

  Cmos0x34 = (UINT8) CmosRead8 (0x34);
  Cmos0x35 = (UINT8) CmosRead8 (0x35);

  return (UINT32) (((UINTN)((Cmos0x35 << 8) + Cmos0x34) << 16) + SIZE_16MB);
}


STATIC
UINT64
GetSystemMemorySizeAbove4gb (
  )
{
  UINT32 Size;
  UINTN  CmosIndex;

  //
  // CMOS 0x5b-0x5d specifies the system memory above 4GB MB.
  // * CMOS(0x5d) is the most significant size byte
  // * CMOS(0x5c) is the middle size byte
  // * CMOS(0x5b) is the least significant size byte
  // * The size is specified in 64kb chunks
  //

  Size = 0;
  for (CmosIndex = 0x5d; CmosIndex >= 0x5b; CmosIndex--) {
    Size = (UINT32) (Size << 8) + (UINT32) CmosRead8 (CmosIndex);
  }

  return LShiftU64 (Size, 16);
}


/**
  Return the highest address that DXE could possibly use, plus one.
**/
STATIC
UINT64
GetFirstNonAddress (
  VOID
  )
{
  UINT64               FirstNonAddress;
  UINT64               Pci64Base, Pci64Size;
  CHAR8                MbString[7 + 1];
  EFI_STATUS           Status;
  FIRMWARE_CONFIG_ITEM FwCfgItem;
  UINTN                FwCfgSize;
  UINT64               HotPlugMemoryEnd;
  RETURN_STATUS        PcdStatus;

  //
  // set FirstNonAddress to suppress incorrect compiler/analyzer warnings
  //
  FirstNonAddress = 0;

  //
  // If QEMU presents an E820 map, then get the highest exclusive >=4GB RAM
  // address from it. This can express an address >= 4GB+1TB.
  //
  // Otherwise, get the flat size of the memory above 4GB from the CMOS (which
  // can only express a size smaller than 1TB), and add it to 4GB.
  //
  Status = ScanOrAdd64BitE820Ram (&FirstNonAddress);
  if (EFI_ERROR (Status)) {
    FirstNonAddress = BASE_4GB + GetSystemMemorySizeAbove4gb ();
  }

  //
  // If DXE is 32-bit, then we're done; PciBusDxe will degrade 64-bit MMIO
  // resources to 32-bit anyway. See DegradeResource() in
  // "PciResourceSupport.c".
  //
#ifdef MDE_CPU_IA32
  if (!FeaturePcdGet (PcdDxeIplSwitchToLongMode)) {
    return FirstNonAddress;
  }
#endif

  //
  // Otherwise, in order to calculate the highest address plus one, we must
  // consider the 64-bit PCI host aperture too. Fetch the default size.
  //
  Pci64Size = PcdGet64 (PcdPciMmio64Size);

  //
  // See if the user specified the number of megabytes for the 64-bit PCI host
  // aperture. The number of non-NUL characters in MbString allows for
  // 9,999,999 MB, which is approximately 10 TB.
  //
  // As signaled by the "X-" prefix, this knob is experimental, and might go
  // away at any time.
  //
  Status = QemuFwCfgFindFile ("opt/ovmf/X-PciMmio64Mb", &FwCfgItem,
             &FwCfgSize);
  if (!EFI_ERROR (Status)) {
    if (FwCfgSize >= sizeof MbString) {
      DEBUG ((EFI_D_WARN,
        "%a: ignoring malformed 64-bit PCI host aperture size from fw_cfg\n",
        __FUNCTION__));
    } else {
      QemuFwCfgSelectItem (FwCfgItem);
      QemuFwCfgReadBytes (FwCfgSize, MbString);
      MbString[FwCfgSize] = '\0';
      Pci64Size = LShiftU64 (AsciiStrDecimalToUint64 (MbString), 20);
    }
  }

  if (Pci64Size == 0) {
    if (mBootMode != BOOT_ON_S3_RESUME) {
      DEBUG ((EFI_D_INFO, "%a: disabling 64-bit PCI host aperture\n",
        __FUNCTION__));
      PcdStatus = PcdSet64S (PcdPciMmio64Size, 0);
      ASSERT_RETURN_ERROR (PcdStatus);
    }

    //
    // There's nothing more to do; the amount of memory above 4GB fully
    // determines the highest address plus one. The memory hotplug area (see
    // below) plays no role for the firmware in this case.
    //
    return FirstNonAddress;
  }

  //
  // The "etc/reserved-memory-end" fw_cfg file, when present, contains an
  // absolute, exclusive end address for the memory hotplug area. This area
  // starts right at the end of the memory above 4GB. The 64-bit PCI host
  // aperture must be placed above it.
  //
  Status = QemuFwCfgFindFile ("etc/reserved-memory-end", &FwCfgItem,
             &FwCfgSize);
  if (!EFI_ERROR (Status) && FwCfgSize == sizeof HotPlugMemoryEnd) {
    QemuFwCfgSelectItem (FwCfgItem);
    QemuFwCfgReadBytes (FwCfgSize, &HotPlugMemoryEnd);
    DEBUG ((DEBUG_VERBOSE, "%a: HotPlugMemoryEnd=0x%Lx\n", __FUNCTION__,
      HotPlugMemoryEnd));

    ASSERT (HotPlugMemoryEnd >= FirstNonAddress);
    FirstNonAddress = HotPlugMemoryEnd;
  }

  //
  // SeaBIOS aligns both boundaries of the 64-bit PCI host aperture to 1GB, so
  // that the host can map it with 1GB hugepages. Follow suit.
  //
  Pci64Base = ALIGN_VALUE (FirstNonAddress, (UINT64)SIZE_1GB);
  Pci64Size = ALIGN_VALUE (Pci64Size, (UINT64)SIZE_1GB);

  //
  // The 64-bit PCI host aperture should also be "naturally" aligned. The
  // alignment is determined by rounding the size of the aperture down to the
  // next smaller or equal power of two. That is, align the aperture by the
  // largest BAR size that can fit into it.
  //
  Pci64Base = ALIGN_VALUE (Pci64Base, GetPowerOfTwo64 (Pci64Size));

  if (mBootMode != BOOT_ON_S3_RESUME) {
    //
    // The core PciHostBridgeDxe driver will automatically add this range to
    // the GCD memory space map through our PciHostBridgeLib instance; here we
    // only need to set the PCDs.
    //
    PcdStatus = PcdSet64S (PcdPciMmio64Base, Pci64Base);
    ASSERT_RETURN_ERROR (PcdStatus);
    PcdStatus = PcdSet64S (PcdPciMmio64Size, Pci64Size);
    ASSERT_RETURN_ERROR (PcdStatus);

    DEBUG ((EFI_D_INFO, "%a: Pci64Base=0x%Lx Pci64Size=0x%Lx\n",
      __FUNCTION__, Pci64Base, Pci64Size));
  }

  //
  // The useful address space ends with the 64-bit PCI host aperture.
  //
  FirstNonAddress = Pci64Base + Pci64Size;
  return FirstNonAddress;
}


/**
  Initialize the mPhysMemAddressWidth variable, based on guest RAM size.
**/
VOID
AddressWidthInitialization (
  VOID
  )
{
  UINT64 FirstNonAddress;

  //
  // As guest-physical memory size grows, the permanent PEI RAM requirements
  // are dominated by the identity-mapping page tables built by the DXE IPL.
  // The DXL IPL keys off of the physical address bits advertized in the CPU
  // HOB. To conserve memory, we calculate the minimum address width here.
  //
  FirstNonAddress      = GetFirstNonAddress ();
  mPhysMemAddressWidth = (UINT8)HighBitSet64 (FirstNonAddress);

  //
  // If FirstNonAddress is not an integral power of two, then we need an
  // additional bit.
  //
  if ((FirstNonAddress & (FirstNonAddress - 1)) != 0) {
    ++mPhysMemAddressWidth;
  }

  //
  // The minimum address width is 36 (covers up to and excluding 64 GB, which
  // is the maximum for Ia32 + PAE). The theoretical architecture maximum for
  // X64 long mode is 52 bits, but the DXE IPL clamps that down to 48 bits. We
  // can simply assert that here, since 48 bits are good enough for 256 TB.
  //
  if (mPhysMemAddressWidth <= 36) {
    mPhysMemAddressWidth = 36;
  }
  ASSERT (mPhysMemAddressWidth <= 48);
}


/**
  Calculate the cap for the permanent PEI memory.
**/
STATIC
UINT32
GetPeiMemoryCap (
  VOID
  )
{
  BOOLEAN Page1GSupport;
  UINT32  RegEax;
  UINT32  RegEdx;
  UINT32  Pml4Entries;
  UINT32  PdpEntries;
  UINTN   TotalPages;

  //
  // If DXE is 32-bit, then just return the traditional 64 MB cap.
  //
#ifdef MDE_CPU_IA32
  if (!FeaturePcdGet (PcdDxeIplSwitchToLongMode)) {
    return SIZE_64MB;
  }
#endif

  //
  // Dependent on physical address width, PEI memory allocations can be
  // dominated by the page tables built for 64-bit DXE. So we key the cap off
  // of those. The code below is based on CreateIdentityMappingPageTables() in
  // "MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c".
  //
  Page1GSupport = FALSE;
  if (PcdGetBool (PcdUse1GPageTable)) {
    AsmCpuid (0x80000000, &RegEax, NULL, NULL, NULL);
    if (RegEax >= 0x80000001) {
      AsmCpuid (0x80000001, NULL, NULL, NULL, &RegEdx);
      if ((RegEdx & BIT26) != 0) {
        Page1GSupport = TRUE;
      }
    }
  }

  if (mPhysMemAddressWidth <= 39) {
    Pml4Entries = 1;
    PdpEntries = 1 << (mPhysMemAddressWidth - 30);
    ASSERT (PdpEntries <= 0x200);
  } else {
    Pml4Entries = 1 << (mPhysMemAddressWidth - 39);
    ASSERT (Pml4Entries <= 0x200);
    PdpEntries = 512;
  }

  TotalPages = Page1GSupport ? Pml4Entries + 1 :
                               (PdpEntries + 1) * Pml4Entries + 1;
  ASSERT (TotalPages <= 0x40201);

  //
  // Add 64 MB for miscellaneous allocations. Note that for
  // mPhysMemAddressWidth values close to 36, the cap will actually be
  // dominated by this increment.
  //
  return (UINT32)(EFI_PAGES_TO_SIZE (TotalPages) + SIZE_64MB);
}


/**
  Publish PEI core memory

  @return EFI_SUCCESS     The PEIM initialized successfully.

**/
EFI_STATUS
PublishPeiMemory (
  VOID
  )
{
  EFI_STATUS                  Status;
  EFI_PHYSICAL_ADDRESS        MemoryBase;
  UINT64                      MemorySize;
  UINT32                      LowerMemorySize;
  UINT32                      PeiMemoryCap;

  LowerMemorySize = GetSystemMemorySizeBelow4gb ();
  if (FeaturePcdGet (PcdSmmSmramRequire)) {
    //
    // TSEG is chipped from the end of low RAM
    //
    LowerMemorySize -= mQ35TsegMbytes * SIZE_1MB;
  }

  //
  // If S3 is supported, then the S3 permanent PEI memory is placed next,
  // downwards. Its size is primarily dictated by CpuMpPei. The formula below
  // is an approximation.
  //
  if (mS3Supported) {
    mS3AcpiReservedMemorySize = SIZE_512KB +
      mMaxCpuCount *
      PcdGet32 (PcdCpuApStackSize);
    mS3AcpiReservedMemoryBase = LowerMemorySize - mS3AcpiReservedMemorySize;
    LowerMemorySize = mS3AcpiReservedMemoryBase;
  }

  if (mBootMode == BOOT_ON_S3_RESUME) {
    MemoryBase = mS3AcpiReservedMemoryBase;
    MemorySize = mS3AcpiReservedMemorySize;
  } else {
    PeiMemoryCap = GetPeiMemoryCap ();
    DEBUG ((EFI_D_INFO, "%a: mPhysMemAddressWidth=%d PeiMemoryCap=%u KB\n",
      __FUNCTION__, mPhysMemAddressWidth, PeiMemoryCap >> 10));

    //
    // Determine the range of memory to use during PEI
    //
    // Technically we could lay the permanent PEI RAM over SEC's temporary
    // decompression and scratch buffer even if "secure S3" is needed, since
    // their lifetimes don't overlap. However, PeiFvInitialization() will cover
    // RAM up to PcdOvmfDecompressionScratchEnd with an EfiACPIMemoryNVS memory
    // allocation HOB, and other allocations served from the permanent PEI RAM
    // shouldn't overlap with that HOB.
    //
    MemoryBase = mS3Supported && FeaturePcdGet (PcdSmmSmramRequire) ?
      PcdGet32 (PcdOvmfDecompressionScratchEnd) :
      PcdGet32 (PcdOvmfDxeMemFvBase) + PcdGet32 (PcdOvmfDxeMemFvSize);
    MemorySize = LowerMemorySize - MemoryBase;
    if (MemorySize > PeiMemoryCap) {
      MemoryBase = LowerMemorySize - PeiMemoryCap;
      MemorySize = PeiMemoryCap;
    }
  }

  //
  // Publish this memory to the PEI Core
  //
  Status = PublishSystemMemory(MemoryBase, MemorySize);
  ASSERT_EFI_ERROR (Status);

  return Status;
}


/**
  Peform Memory Detection for QEMU / KVM

**/
STATIC
VOID
QemuInitializeRam (
  VOID
  )
{
  UINT64                      LowerMemorySize;
  UINT64                      UpperMemorySize;
  MTRR_SETTINGS               MtrrSettings;
  EFI_STATUS                  Status;

  DEBUG ((EFI_D_INFO, "%a called\n", __FUNCTION__));

  //
  // Determine total memory size available
  //
  LowerMemorySize = GetSystemMemorySizeBelow4gb ();
  UpperMemorySize = GetSystemMemorySizeAbove4gb ();

  if (mBootMode == BOOT_ON_S3_RESUME) {
    //
    // Create the following memory HOB as an exception on the S3 boot path.
    //
    // Normally we'd create memory HOBs only on the normal boot path. However,
    // CpuMpPei specifically needs such a low-memory HOB on the S3 path as
    // well, for "borrowing" a subset of it temporarily, for the AP startup
    // vector.
    //
    // CpuMpPei saves the original contents of the borrowed area in permanent
    // PEI RAM, in a backup buffer allocated with the normal PEI services.
    // CpuMpPei restores the original contents ("returns" the borrowed area) at
    // End-of-PEI. End-of-PEI in turn is emitted by S3Resume2Pei before
    // transferring control to the OS's wakeup vector in the FACS.
    //
    // We expect any other PEIMs that "borrow" memory similarly to CpuMpPei to
    // restore the original contents. Furthermore, we expect all such PEIMs
    // (CpuMpPei included) to claim the borrowed areas by producing memory
    // allocation HOBs, and to honor preexistent memory allocation HOBs when
    // looking for an area to borrow.
    //
    AddMemoryRangeHob (0, BASE_512KB + BASE_128KB);
  } else {
    //
    // Create memory HOBs
    //
    AddMemoryRangeHob (0, BASE_512KB + BASE_128KB);

    if (FeaturePcdGet (PcdSmmSmramRequire)) {
      UINT32 TsegSize;

      TsegSize = mQ35TsegMbytes * SIZE_1MB;
      AddMemoryRangeHob (BASE_1MB, LowerMemorySize - TsegSize);
      AddReservedMemoryBaseSizeHob (LowerMemorySize - TsegSize, TsegSize,
        TRUE);
    } else {
      AddMemoryRangeHob (BASE_1MB, LowerMemorySize);
    }

    //
    // If QEMU presents an E820 map, then create memory HOBs for the >=4GB RAM
    // entries. Otherwise, create a single memory HOB with the flat >=4GB
    // memory size read from the CMOS.
    //
    Status = ScanOrAdd64BitE820Ram (NULL);
    if (EFI_ERROR (Status) && UpperMemorySize != 0) {
      AddMemoryBaseSizeHob (BASE_4GB, UpperMemorySize);
    }
  }

  //
  // We'd like to keep the following ranges uncached:
  // - [640 KB, 1 MB)
  // - [LowerMemorySize, 4 GB)
  //
  // Everything else should be WB. Unfortunately, programming the inverse (ie.
  // keeping the default UC, and configuring the complement set of the above as
  // WB) is not reliable in general, because the end of the upper RAM can have
  // practically any alignment, and we may not have enough variable MTRRs to
  // cover it exactly.
  //
  if (IsMtrrSupported ()) {
    MtrrGetAllMtrrs (&MtrrSettings);

    //
    // MTRRs disabled, fixed MTRRs disabled, default type is uncached
    //
    ASSERT ((MtrrSettings.MtrrDefType & BIT11) == 0);
    ASSERT ((MtrrSettings.MtrrDefType & BIT10) == 0);
    ASSERT ((MtrrSettings.MtrrDefType & 0xFF) == 0);

    //
    // flip default type to writeback
    //
    SetMem (&MtrrSettings.Fixed, sizeof MtrrSettings.Fixed, 0x06);
    ZeroMem (&MtrrSettings.Variables, sizeof MtrrSettings.Variables);
    MtrrSettings.MtrrDefType |= BIT11 | BIT10 | 6;
    MtrrSetAllMtrrs (&MtrrSettings);

    //
    // Set memory range from 640KB to 1MB to uncacheable
    //
    Status = MtrrSetMemoryAttribute (BASE_512KB + BASE_128KB,
               BASE_1MB - (BASE_512KB + BASE_128KB), CacheUncacheable);
    ASSERT_EFI_ERROR (Status);

    //
    // Set memory range from the "top of lower RAM" (RAM below 4GB) to 4GB as
    // uncacheable
    //
    Status = MtrrSetMemoryAttribute (LowerMemorySize,
               SIZE_4GB - LowerMemorySize, CacheUncacheable);
    ASSERT_EFI_ERROR (Status);
  }
}

/**
  Publish system RAM and reserve memory regions

**/
VOID
InitializeRamRegions (
  VOID
  )
{
  if (!mXen) {
    QemuInitializeRam ();
  } else {
    XenPublishRamRegions ();
  }

  if (mS3Supported && mBootMode != BOOT_ON_S3_RESUME) {
    //
    // This is the memory range that will be used for PEI on S3 resume
    //
    BuildMemoryAllocationHob (
      mS3AcpiReservedMemoryBase,
      mS3AcpiReservedMemorySize,
      EfiACPIMemoryNVS
      );

    //
    // Cover the initial RAM area used as stack and temporary PEI heap.
    //
    // This is reserved as ACPI NVS so it can be used on S3 resume.
    //
    BuildMemoryAllocationHob (
      PcdGet32 (PcdOvmfSecPeiTempRamBase),
      PcdGet32 (PcdOvmfSecPeiTempRamSize),
      EfiACPIMemoryNVS
      );

    //
    // SEC stores its table of GUIDed section handlers here.
    //
    BuildMemoryAllocationHob (
      PcdGet64 (PcdGuidedExtractHandlerTableAddress),
      PcdGet32 (PcdGuidedExtractHandlerTableSize),
      EfiACPIMemoryNVS
      );

#ifdef MDE_CPU_X64
    //
    // Reserve the initial page tables built by the reset vector code.
    //
    // Since this memory range will be used by the Reset Vector on S3
    // resume, it must be reserved as ACPI NVS.
    //
    BuildMemoryAllocationHob (
      (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdOvmfSecPageTablesBase),
      (UINT64)(UINTN) PcdGet32 (PcdOvmfSecPageTablesSize),
      EfiACPIMemoryNVS
      );
#endif
  }

  if (mBootMode != BOOT_ON_S3_RESUME) {
    if (!FeaturePcdGet (PcdSmmSmramRequire)) {
      //
      // Reserve the lock box storage area
      //
      // Since this memory range will be used on S3 resume, it must be
      // reserved as ACPI NVS.
      //
      // If S3 is unsupported, then various drivers might still write to the
      // LockBox area. We ought to prevent DXE from serving allocation requests
      // such that they would overlap the LockBox storage.
      //
      ZeroMem (
        (VOID*)(UINTN) PcdGet32 (PcdOvmfLockBoxStorageBase),
        (UINTN) PcdGet32 (PcdOvmfLockBoxStorageSize)
        );
      BuildMemoryAllocationHob (
        (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdOvmfLockBoxStorageBase),
        (UINT64)(UINTN) PcdGet32 (PcdOvmfLockBoxStorageSize),
        mS3Supported ? EfiACPIMemoryNVS : EfiBootServicesData
        );
    }

    if (FeaturePcdGet (PcdSmmSmramRequire)) {
      UINT32 TsegSize;

      //
      // Make sure the TSEG area that we reported as a reserved memory resource
      // cannot be used for reserved memory allocations.
      //
      TsegSize = mQ35TsegMbytes * SIZE_1MB;
      BuildMemoryAllocationHob (
        GetSystemMemorySizeBelow4gb() - TsegSize,
        TsegSize,
        EfiReservedMemoryType
        );
    }
  }
}