[mirror_edk2.git] / OvmfPkg / Library / PlatformInitLib / MemDetect.c

/**@file
  Memory Detection for Virtual Machines.

  Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

Module Name:

  MemDetect.c

**/

//
// The package level header files this module uses
//
#include <IndustryStandard/E820.h>
#include <IndustryStandard/I440FxPiix4.h>
#include <IndustryStandard/Q35MchIch9.h>
#include <IndustryStandard/CloudHv.h>
#include <IndustryStandard/Xen/arch-x86/hvm/start_info.h>
#include <PiPei.h>
#include <Register/Intel/SmramSaveStateMap.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/MemEncryptSevLib.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 <Library/QemuFwCfgSimpleParserLib.h>
#include <Library/TdxLib.h>

#include <Library/PlatformInitLib.h>

VOID
EFIAPI
PlatformQemuUc32BaseInitialization (
  IN OUT EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
  )
{
  UINT32  LowerMemorySize;

  if (PlatformInfoHob->HostBridgeDevId == 0xffff /* microvm */) {
    return;
  }

  if (PlatformInfoHob->HostBridgeDevId == INTEL_Q35_MCH_DEVICE_ID) {
    //
    // On q35, the 32-bit area that we'll mark as UC, through variable MTRRs,
    // starts at PcdPciExpressBaseAddress. The platform DSC is responsible for
    // setting PcdPciExpressBaseAddress such that describing the
    // [PcdPciExpressBaseAddress, 4GB) range require a very small number of
    // variable MTRRs (preferably 1 or 2).
    //
    ASSERT (PcdGet64 (PcdPciExpressBaseAddress) <= MAX_UINT32);
    PlatformInfoHob->Uc32Base = (UINT32)PcdGet64 (PcdPciExpressBaseAddress);
    return;
  }

  if (PlatformInfoHob->HostBridgeDevId == CLOUDHV_DEVICE_ID) {
    PlatformInfoHob->Uc32Size = CLOUDHV_MMIO_HOLE_SIZE;
    PlatformInfoHob->Uc32Base = CLOUDHV_MMIO_HOLE_ADDRESS;
    return;
  }

  ASSERT (PlatformInfoHob->HostBridgeDevId == INTEL_82441_DEVICE_ID);
  //
  // On i440fx, start with the [LowerMemorySize, 4GB) range. Make sure one
  // variable MTRR suffices by truncating the size to a whole power of two,
  // while keeping the end affixed to 4GB. This will round the base up.
  //
  LowerMemorySize           = PlatformGetSystemMemorySizeBelow4gb (PlatformInfoHob);
  PlatformInfoHob->Uc32Size = GetPowerOfTwo32 ((UINT32)(SIZE_4GB - LowerMemorySize));
  PlatformInfoHob->Uc32Base = (UINT32)(SIZE_4GB - PlatformInfoHob->Uc32Size);
  //
  // Assuming that LowerMemorySize is at least 1 byte, Uc32Size is at most 2GB.
  // Therefore Uc32Base is at least 2GB.
  //
  ASSERT (PlatformInfoHob->Uc32Base >= BASE_2GB);

  if (PlatformInfoHob->Uc32Base != LowerMemorySize) {
    DEBUG ((
      DEBUG_VERBOSE,
      "%a: rounded UC32 base from 0x%x up to 0x%x, for "
      "an UC32 size of 0x%x\n",
      __FUNCTION__,
      LowerMemorySize,
      PlatformInfoHob->Uc32Base,
      PlatformInfoHob->Uc32Size
      ));
  }
}

/**
  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 PlatformScanOrAdd64BitE820Ram()
                          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
PlatformScanOrAdd64BitE820Ram (
  IN BOOLEAN  AddHighHob,
  OUT UINT64  *LowMemory OPTIONAL,
  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 (LowMemory != NULL) {
    *LowMemory = 0;
  }

  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) {
      if (AddHighHob && (E820Entry.BaseAddr >= BASE_4GB)) {
        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) {
          PlatformAddMemoryRangeHob (Base, End);
          DEBUG ((
            DEBUG_VERBOSE,
            "%a: PlatformAddMemoryRangeHob [0x%Lx, 0x%Lx)\n",
            __FUNCTION__,
            Base,
            End
            ));
        }
      }

      if (MaxAddress || LowMemory) {
        UINT64  Candidate;

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

        if (LowMemory && (Candidate > *LowMemory) && (Candidate < BASE_4GB)) {
          *LowMemory = Candidate;
          DEBUG ((
            DEBUG_VERBOSE,
            "%a: LowMemory=0x%Lx\n",
            __FUNCTION__,
            *LowMemory
            ));
        }
      }
    }
  }

  return EFI_SUCCESS;
}

/**
  Returns PVH memmap

  @param Entries      Pointer to PVH memmap
  @param Count        Number of entries

  @return EFI_STATUS
**/
EFI_STATUS
GetPvhMemmapEntries (
  struct hvm_memmap_table_entry  **Entries,
  UINT32                         *Count
  )
{
  UINT32                 *PVHResetVectorData;
  struct hvm_start_info  *pvh_start_info;

  PVHResetVectorData = (VOID *)(UINTN)PcdGet32 (PcdXenPvhStartOfDayStructPtr);
  if (PVHResetVectorData == 0) {
    return EFI_NOT_FOUND;
  }

  pvh_start_info = (struct hvm_start_info *)(UINTN)PVHResetVectorData[0];

  *Entries = (struct hvm_memmap_table_entry *)(UINTN)pvh_start_info->memmap_paddr;
  *Count   = pvh_start_info->memmap_entries;

  return EFI_SUCCESS;
}

STATIC
UINT64
GetHighestSystemMemoryAddressFromPvhMemmap (
  BOOLEAN  Below4gb
  )
{
  struct hvm_memmap_table_entry  *Memmap;
  UINT32                         MemmapEntriesCount;
  struct hvm_memmap_table_entry  *Entry;
  EFI_STATUS                     Status;
  UINT32                         Loop;
  UINT64                         HighestAddress;
  UINT64                         EntryEnd;

  HighestAddress = 0;

  Status = GetPvhMemmapEntries (&Memmap, &MemmapEntriesCount);
  ASSERT_EFI_ERROR (Status);

  for (Loop = 0; Loop < MemmapEntriesCount; Loop++) {
    Entry    = Memmap + Loop;
    EntryEnd = Entry->addr + Entry->size;

    if ((Entry->type == XEN_HVM_MEMMAP_TYPE_RAM) &&
        (EntryEnd > HighestAddress))
    {
      if (Below4gb && (EntryEnd <= BASE_4GB)) {
        HighestAddress = EntryEnd;
      } else if (!Below4gb && (EntryEnd >= BASE_4GB)) {
        HighestAddress = EntryEnd;
      }
    }
  }

  return HighestAddress;
}

UINT32
EFIAPI
PlatformGetSystemMemorySizeBelow4gb (
  IN EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
  )
{
  EFI_STATUS  Status;
  UINT64      LowerMemorySize = 0;
  UINT8       Cmos0x34;
  UINT8       Cmos0x35;

  if (PlatformInfoHob->HostBridgeDevId == CLOUDHV_DEVICE_ID) {
    // Get the information from PVH memmap
    return (UINT32)GetHighestSystemMemoryAddressFromPvhMemmap (TRUE);
  }

  Status = PlatformScanOrAdd64BitE820Ram (FALSE, &LowerMemorySize, NULL);
  if ((Status == EFI_SUCCESS) && (LowerMemorySize > 0)) {
    return (UINT32)LowerMemorySize;
  }

  //
  // 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)PlatformCmosRead8 (0x34);
  Cmos0x35 = (UINT8)PlatformCmosRead8 (0x35);

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

STATIC
UINT64
PlatformGetSystemMemorySizeAbove4gb (
  )
{
  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)PlatformCmosRead8 (CmosIndex);
  }

  return LShiftU64 (Size, 16);
}

/**
  Return the highest address that DXE could possibly use, plus one.
**/
STATIC
UINT64
PlatformGetFirstNonAddress (
  IN OUT  EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
  )
{
  UINT64                FirstNonAddress;
  UINT32                FwCfgPciMmio64Mb;
  EFI_STATUS            Status;
  FIRMWARE_CONFIG_ITEM  FwCfgItem;
  UINTN                 FwCfgSize;
  UINT64                HotPlugMemoryEnd;

  //
  // 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 = PlatformScanOrAdd64BitE820Ram (FALSE, NULL, &FirstNonAddress);
  if (EFI_ERROR (Status)) {
    FirstNonAddress = BASE_4GB + PlatformGetSystemMemorySizeAbove4gb ();
  }

  //
  // 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

  //
  // See if the user specified the number of megabytes for the 64-bit PCI host
  // aperture. Accept an aperture size up to 16TB.
  //
  // As signaled by the "X-" prefix, this knob is experimental, and might go
  // away at any time.
  //
  Status = QemuFwCfgParseUint32 (
             "opt/ovmf/X-PciMmio64Mb",
             FALSE,
             &FwCfgPciMmio64Mb
             );
  switch (Status) {
    case EFI_UNSUPPORTED:
    case EFI_NOT_FOUND:
      break;
    case EFI_SUCCESS:
      if (FwCfgPciMmio64Mb <= 0x1000000) {
        PlatformInfoHob->PcdPciMmio64Size = LShiftU64 (FwCfgPciMmio64Mb, 20);
        break;
      }

    //
    // fall through
    //
    default:
      DEBUG ((
        DEBUG_WARN,
        "%a: ignoring malformed 64-bit PCI host aperture size from fw_cfg\n",
        __FUNCTION__
        ));
      break;
  }

  if (PlatformInfoHob->PcdPciMmio64Size == 0) {
    if (PlatformInfoHob->BootMode != BOOT_ON_S3_RESUME) {
      DEBUG ((
        DEBUG_INFO,
        "%a: disabling 64-bit PCI host aperture\n",
        __FUNCTION__
        ));
    }

    //
    // 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.
  //
  PlatformInfoHob->PcdPciMmio64Base = ALIGN_VALUE (FirstNonAddress, (UINT64)SIZE_1GB);
  PlatformInfoHob->PcdPciMmio64Size = ALIGN_VALUE (PlatformInfoHob->PcdPciMmio64Size, (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.
  //
  PlatformInfoHob->PcdPciMmio64Base = ALIGN_VALUE (PlatformInfoHob->PcdPciMmio64Base, GetPowerOfTwo64 (PlatformInfoHob->PcdPciMmio64Size));

  //
  // The useful address space ends with the 64-bit PCI host aperture.
  //
  FirstNonAddress = PlatformInfoHob->PcdPciMmio64Base + PlatformInfoHob->PcdPciMmio64Size;
  return FirstNonAddress;
}

/**
  Initialize the PhysMemAddressWidth field in PlatformInfoHob based on guest RAM size.
**/
VOID
EFIAPI
PlatformAddressWidthInitialization (
  IN OUT EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
  )
{
  UINT64  FirstNonAddress;
  UINT8   PhysMemAddressWidth;

  //
  // 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     = PlatformGetFirstNonAddress (PlatformInfoHob);
  PhysMemAddressWidth = (UINT8)HighBitSet64 (FirstNonAddress);

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

  //
  // 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 (PhysMemAddressWidth <= 36) {
    PhysMemAddressWidth = 36;
  }

 #if defined (MDE_CPU_X64)
  if (TdIsEnabled ()) {
    if (TdSharedPageMask () == (1ULL << 47)) {
      PhysMemAddressWidth = 48;
    } else {
      PhysMemAddressWidth = 52;
    }
  }

  ASSERT (PhysMemAddressWidth <= 52);
 #else
  ASSERT (PhysMemAddressWidth <= 48);
 #endif

  PlatformInfoHob->FirstNonAddress     = FirstNonAddress;
  PlatformInfoHob->PhysMemAddressWidth = PhysMemAddressWidth;
}

STATIC
VOID
QemuInitializeRamBelow1gb (
  IN EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
  )
{
  if (PlatformInfoHob->SmmSmramRequire && PlatformInfoHob->Q35SmramAtDefaultSmbase) {
    PlatformAddMemoryRangeHob (0, SMM_DEFAULT_SMBASE);
    PlatformAddReservedMemoryBaseSizeHob (
      SMM_DEFAULT_SMBASE,
      MCH_DEFAULT_SMBASE_SIZE,
      TRUE /* Cacheable */
      );
    STATIC_ASSERT (
      SMM_DEFAULT_SMBASE + MCH_DEFAULT_SMBASE_SIZE < BASE_512KB + BASE_128KB,
      "end of SMRAM at default SMBASE ends at, or exceeds, 640KB"
      );
    PlatformAddMemoryRangeHob (
      SMM_DEFAULT_SMBASE + MCH_DEFAULT_SMBASE_SIZE,
      BASE_512KB + BASE_128KB
      );
  } else {
    PlatformAddMemoryRangeHob (0, BASE_512KB + BASE_128KB);
  }
}

/**
  Peform Memory Detection for QEMU / KVM

**/
VOID
EFIAPI
PlatformQemuInitializeRam (
  IN EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
  )
{
  UINT64         LowerMemorySize;
  UINT64         UpperMemorySize;
  MTRR_SETTINGS  MtrrSettings;
  EFI_STATUS     Status;

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

  //
  // Determine total memory size available
  //
  LowerMemorySize = PlatformGetSystemMemorySizeBelow4gb (PlatformInfoHob);

  if (PlatformInfoHob->BootMode == 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.
    //
    QemuInitializeRamBelow1gb (PlatformInfoHob);
  } else {
    //
    // Create memory HOBs
    //
    QemuInitializeRamBelow1gb (PlatformInfoHob);

    if (PlatformInfoHob->SmmSmramRequire) {
      UINT32  TsegSize;

      TsegSize = PlatformInfoHob->Q35TsegMbytes * SIZE_1MB;
      PlatformAddMemoryRangeHob (BASE_1MB, LowerMemorySize - TsegSize);
      PlatformAddReservedMemoryBaseSizeHob (
        LowerMemorySize - TsegSize,
        TsegSize,
        TRUE
        );
    } else {
      PlatformAddMemoryRangeHob (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 = PlatformScanOrAdd64BitE820Ram (TRUE, NULL, NULL);
    if (EFI_ERROR (Status)) {
      UpperMemorySize = PlatformGetSystemMemorySizeAbove4gb ();
      if (UpperMemorySize != 0) {
        PlatformAddMemoryBaseSizeHob (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 () && (PlatformInfoHob->HostBridgeDevId != CLOUDHV_DEVICE_ID)) {
    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 the memory range from the start of the 32-bit MMIO area (32-bit PCI
    // MMIO aperture on i440fx, PCIEXBAR on q35) to 4GB as uncacheable.
    //
    Status = MtrrSetMemoryAttribute (
               PlatformInfoHob->Uc32Base,
               SIZE_4GB - PlatformInfoHob->Uc32Base,
               CacheUncacheable
               );
    ASSERT_EFI_ERROR (Status);
  }
}

VOID
EFIAPI
PlatformQemuInitializeRamForS3 (
  IN EFI_HOB_PLATFORM_INFO  *PlatformInfoHob
  )
{
  if (PlatformInfoHob->S3Supported && (PlatformInfoHob->BootMode != BOOT_ON_S3_RESUME)) {
    //
    // This is the memory range that will be used for PEI on S3 resume
    //
    BuildMemoryAllocationHob (
      PlatformInfoHob->S3AcpiReservedMemoryBase,
      PlatformInfoHob->S3AcpiReservedMemorySize,
      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
      );

    if (PlatformInfoHob->SevEsIsEnabled) {
      //
      // If SEV-ES is enabled, reserve the GHCB-related memory area. This
      // includes the extra page table used to break down the 2MB page
      // mapping into 4KB page entries where the GHCB resides and the
      // GHCB area itself.
      //
      // 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 (PcdOvmfSecGhcbPageTableBase),
        (UINT64)(UINTN)PcdGet32 (PcdOvmfSecGhcbPageTableSize),
        EfiACPIMemoryNVS
        );
      BuildMemoryAllocationHob (
        (EFI_PHYSICAL_ADDRESS)(UINTN)PcdGet32 (PcdOvmfSecGhcbBase),
        (UINT64)(UINTN)PcdGet32 (PcdOvmfSecGhcbSize),
        EfiACPIMemoryNVS
        );
      BuildMemoryAllocationHob (
        (EFI_PHYSICAL_ADDRESS)(UINTN)PcdGet32 (PcdOvmfSecGhcbBackupBase),
        (UINT64)(UINTN)PcdGet32 (PcdOvmfSecGhcbBackupSize),
        EfiACPIMemoryNVS
        );
    }

 #endif
  }

  if (PlatformInfoHob->BootMode != BOOT_ON_S3_RESUME) {
    if (!PlatformInfoHob->SmmSmramRequire) {
      //
      // 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),
        PlatformInfoHob->S3Supported ? EfiACPIMemoryNVS : EfiBootServicesData
        );
    }

    if (PlatformInfoHob->SmmSmramRequire) {
      UINT32  TsegSize;

      //
      // Make sure the TSEG area that we reported as a reserved memory resource
      // cannot be used for reserved memory allocations.
      //
      TsegSize = PlatformInfoHob->Q35TsegMbytes * SIZE_1MB;
      BuildMemoryAllocationHob (
        PlatformGetSystemMemorySizeBelow4gb (PlatformInfoHob) - TsegSize,
        TsegSize,
        EfiReservedMemoryType
        );
      //
      // Similarly, allocate away the (already reserved) SMRAM at the default
      // SMBASE, if it exists.
      //
      if (PlatformInfoHob->Q35SmramAtDefaultSmbase) {
        BuildMemoryAllocationHob (
          SMM_DEFAULT_SMBASE,
          MCH_DEFAULT_SMBASE_SIZE,
          EfiReservedMemoryType
          );
      }
    }

 #ifdef MDE_CPU_X64
    if (FixedPcdGet32 (PcdOvmfWorkAreaSize) != 0) {
      //
      // Reserve the work area.
      //
      // Since this memory range will be used by the Reset Vector on S3
      // resume, it must be reserved as ACPI NVS.
      //
      // If S3 is unsupported, then various drivers might still write to the
      // work area. We ought to prevent DXE from serving allocation requests
      // such that they would overlap the work area.
      //
      BuildMemoryAllocationHob (
        (EFI_PHYSICAL_ADDRESS)(UINTN)FixedPcdGet32 (PcdOvmfWorkAreaBase),
        (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfWorkAreaSize),
        PlatformInfoHob->S3Supported ? EfiACPIMemoryNVS : EfiBootServicesData
        );
    }

 #endif
  }
}