diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index d59b461..9ee4b59 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -39,6 +39,9 @@
 
 UINT8 mPhysMemAddressWidth;
 
+STATIC UINT32 mS3AcpiReservedMemoryBase;
+STATIC UINT32 mS3AcpiReservedMemorySize;
+
 UINT32
 GetSystemMemorySizeBelow4gb (
   VOID
@@ -335,18 +338,31 @@
   UINT64                      LowerMemorySize;
   UINT32                      PeiMemoryCap;
 
-  if (mBootMode == BOOT_ON_S3_RESUME) {
-    MemoryBase = PcdGet32 (PcdS3AcpiReservedMemoryBase);
-    MemorySize = PcdGet32 (PcdS3AcpiReservedMemorySize);
-  } else {
-    LowerMemorySize = GetSystemMemorySizeBelow4gb ();
-    if (FeaturePcdGet (PcdSmmSmramRequire)) {
-      //
-      // TSEG is chipped from the end of low RAM
-      //
-      LowerMemorySize -= FixedPcdGet8 (PcdQ35TsegMbytes) * SIZE_1MB;
-    }
+  LowerMemorySize = GetSystemMemorySizeBelow4gb ();
+  if (FeaturePcdGet (PcdSmmSmramRequire)) {
+    //
+    // TSEG is chipped from the end of low RAM
+    //
+    LowerMemorySize -= FixedPcdGet8 (PcdQ35TsegMbytes) * 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 +
+      PcdGet32 (PcdCpuMaxLogicalProcessorNumber) *
+      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));
@@ -514,8 +530,8 @@
     // This is the memory range that will be used for PEI on S3 resume
     //
     BuildMemoryAllocationHob (
-      (EFI_PHYSICAL_ADDRESS)(UINTN) PcdGet32 (PcdS3AcpiReservedMemoryBase),
-      (UINT64)(UINTN) PcdGet32 (PcdS3AcpiReservedMemorySize),
+      mS3AcpiReservedMemoryBase,
+      mS3AcpiReservedMemorySize,
       EfiACPIMemoryNVS
       );
 
diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 3556404..5d765ba 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -65,7 +65,6 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPeiMemFvSize
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDxeMemFvBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDxeMemFvSize
-  gUefiOvmfPkgTokenSpaceGuid.PcdS3AcpiReservedMemoryBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPageTablesBase
@@ -82,7 +81,6 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio64Size
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35TsegMbytes
-  gEfiIntelFrameworkModulePkgTokenSpaceGuid.PcdS3AcpiReservedMemorySize
   gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress
   gEfiMdeModulePkgTokenSpaceGuid.PcdVariableStoreSize
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize
@@ -95,6 +93,8 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdPropertiesTableEnable
   gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiS3Enable
   gUefiCpuPkgTokenSpaceGuid.PcdCpuLocalApicBaseAddress
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuMaxLogicalProcessorNumber
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuApStackSize
 
 [FixedPcd]
   gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress