diff --git a/Library/OcAcpiLib/OcAcpiLib.c b/Library/OcAcpiLib/OcAcpiLib.c
index 76e0c1592f989cc556773aefb6a7680b0f7e5822..c242bbb3d8e60bb1bfb602029c3456333600cd19 100755
--- a/Library/OcAcpiLib/OcAcpiLib.c
+++ b/Library/OcAcpiLib/OcAcpiLib.c
@@ -263,6 +263,170 @@ AcpiFindName (
   return 0;
 }
 
+STATIC
+VOID
+AcpiRefreshTableChecksum (
+  IN EFI_ACPI_DESCRIPTION_HEADER  *Table
+  )
+{
+  UINT32      TablePrintSignature;
+
+  TablePrintSignature = AcpiReadSignature ((EFI_ACPI_COMMON_HEADER *) Table);
+  Table->Checksum     = 0;
+  Table->Checksum     = CalculateCheckSum8 ((UINT8 *) Table, Table->Length);
+
+  DEBUG ((
+    DEBUG_INFO,
+    "OCA: Refreshed %.4a checksum to %02x\n",
+    (CHAR8 *) &TablePrintSignature,
+    Table->Checksum
+    ));
+}
+
+STATIC
+BOOLEAN
+AcpiIsTableWritable (
+  IN     EFI_ACPI_COMMON_HEADER  *Table
+  )
+{
+  UINT32  LengthOriginal;
+
+  LengthOriginal = Table->Length;
+  (*(volatile UINT32 *)&Table->Length)++;
+
+  if (LengthOriginal == *(volatile UINT32 *)&Table->Length) {
+    return FALSE;
+  }
+
+  Table->Length = LengthOriginal;
+  return TRUE;
+}
+
+STATIC
+EFI_STATUS
+AcpiAllocateCopyTable (
+  IN     EFI_ACPI_COMMON_HEADER  *Table,
+  IN     UINT32                  NewSize OPTIONAL,
+     OUT EFI_ACPI_COMMON_HEADER  **NewTable
+  )
+{
+  EFI_STATUS              Status;
+  UINT32                  TablePrintSignature;
+  EFI_PHYSICAL_ADDRESS    NewTableAddress;
+
+  if (NewSize < Table->Length) {
+    NewSize = Table->Length;
+  }
+
+  TablePrintSignature = AcpiReadSignature (Table);
+
+  NewTableAddress = BASE_4GB - 1;
+  Status = gBS->AllocatePages (
+    AllocateMaxAddress,
+    EfiACPIMemoryNVS,
+    EFI_SIZE_TO_PAGES (NewSize),
+    &NewTableAddress
+    );
+  if (EFI_ERROR (Status)) {
+    DEBUG ((
+      DEBUG_WARN,
+      "OCA: Failed to allocate %u bytes for table %.4a\n",
+      NewSize,
+      (CHAR8 *) &TablePrintSignature
+      ));
+    return Status;
+  }
+
+  *NewTable = (EFI_ACPI_COMMON_HEADER *)(UINTN) NewTableAddress;
+
+  DEBUG ((
+    DEBUG_INFO,
+    "OCA: Allocated new table %.4a at %p\n",
+    (CHAR8 *) &TablePrintSignature,
+    *NewTable
+    ));
+
+  CopyMem (*NewTable, Table, Table->Length);
+  ZeroMem (((UINT8 *) *NewTable) + Table->Length, EFI_PAGES_TO_SIZE (EFI_SIZE_TO_PAGES (NewSize)) - Table->Length);
+  (*NewTable)->Length = NewSize;
+
+  return EFI_SUCCESS;
+}
+
+STATIC
+EFI_STATUS
+AcpiAllocateCopyFadt (
+  IN OUT OC_ACPI_CONTEXT             *Context,
+  IN     UINT32                      NewSize
+  )
+{
+  EFI_STATUS              Status;
+  EFI_ACPI_COMMON_HEADER  *NewFadt;
+  UINT32                  Index;
+
+  Status = AcpiAllocateCopyTable (
+    (EFI_ACPI_COMMON_HEADER *) Context->Fadt,
+    NewSize,
+    &NewFadt
+    );
+  if (EFI_ERROR (Status)) {
+    return Status;
+  }
+
+  for (Index = 0; Index < Context->NumberOfTables; ++Index) {
+    //
+    // There is a possibility for multiple FADT tables.
+    //
+    if (Context->Tables[Index]->Signature == EFI_ACPI_6_2_FIXED_ACPI_DESCRIPTION_TABLE_SIGNATURE) {
+      Context->Tables[Index] = NewFadt;
+    }
+  }
+  Context->Fadt = (EFI_ACPI_6_2_FIXED_ACPI_DESCRIPTION_TABLE *) NewFadt;
+
+  return EFI_SUCCESS;
+}
+
+STATIC
+EFI_STATUS
+AcpiAllocateCopyDsdt (
+  IN OUT OC_ACPI_CONTEXT             *Context,
+  IN     EFI_ACPI_DESCRIPTION_HEADER *NewDsdt     OPTIONAL
+  )
+{
+  EFI_STATUS              Status;
+  EFI_ACPI_COMMON_HEADER  *AllocatedDsdt;
+
+  Status = AcpiAllocateCopyTable (
+    (EFI_ACPI_COMMON_HEADER *) (NewDsdt != NULL ? NewDsdt : Context->Dsdt),
+    0,
+    &AllocatedDsdt
+    );
+  if (EFI_ERROR (Status)) {
+    return Status;
+  }
+
+  //
+  // Reallocate FADT if needed.
+  //
+  if (!AcpiIsTableWritable ((EFI_ACPI_COMMON_HEADER *) Context->Fadt)) {
+    Status = AcpiAllocateCopyFadt (Context, 0);
+    if (EFI_ERROR (Status)) {
+      FreePool (AllocatedDsdt);
+      return Status;
+    }
+  }
+
+  if (Context->Fadt->Header.Length >= OFFSET_OF (EFI_ACPI_6_2_FIXED_ACPI_DESCRIPTION_TABLE, XDsdt) + sizeof (Context->Fadt->XDsdt)) {
+    Context->Fadt->XDsdt = (UINT64)(UINTN) AllocatedDsdt;
+  }
+  Context->Fadt->Dsdt = (UINT32)(UINTN) AllocatedDsdt;
+  AcpiRefreshTableChecksum ((EFI_ACPI_DESCRIPTION_HEADER *) Context->Fadt);
+
+  Context->Dsdt = (EFI_ACPI_DESCRIPTION_HEADER *) AllocatedDsdt;
+
+  return EFI_SUCCESS;
+}
+
 /**
   Load ACPI table regions.
 
@@ -624,6 +788,15 @@ AcpiInitContext (
         Context->Dsdt->Length,
         Index
         ));
+
+      if ((UINTN)Context->Dsdt < BASE_1MB) {
+        DEBUG ((
+          DEBUG_INFO,
+          "OCA: Unlocking DSDT at %p\n",
+          Context->Dsdt
+          ));
+        LegacyRegionUnlock ((UINT32)(UINTN)Context->Tables[DstIndex], Context->Tables[DstIndex]->Length);
+      }
     }
 
     ++DstIndex;
@@ -850,7 +1023,7 @@ AcpiInsertTable (
 {
   EFI_ACPI_COMMON_HEADER    *Common;
   EFI_STATUS                Status;
-  EFI_PHYSICAL_ADDRESS      Table;
+  EFI_ACPI_COMMON_HEADER    *NewTable;
   EFI_ACPI_COMMON_HEADER    **NewTables;
   BOOLEAN                   ReplaceDsdt;
   UINT32                    TablePrintSignature;
@@ -887,54 +1060,37 @@ AcpiInsertTable (
     Context->AllocatedTables += 2;
   }
 
-  Table = BASE_4GB - 1;
-  Status = gBS->AllocatePages (
-          AllocateMaxAddress,
-          EfiACPIMemoryNVS,
-          EFI_SIZE_TO_PAGES (Length),
-          &Table
-          );
-
-  if (EFI_ERROR (Status)) {
-    DEBUG ((DEBUG_WARN, "OCA: Failed to allocate %u bytes for inserted ACPI table\n", Length));
-    return Status;
-  }
-
-  CopyMem ((UINT8 *)(UINTN)Table, Data, Length);
-  ZeroMem ((UINT8 *)(UINTN)Table + Length, EFI_PAGES_TO_SIZE (EFI_SIZE_TO_PAGES (Length)) - Length);
-
   if (ReplaceDsdt) {
     DEBUG ((
       DEBUG_INFO,
       "OCA: Replaced DSDT of %u bytes into ACPI\n",
       Common->Length
       ));
-    Context->Dsdt = (EFI_ACPI_DESCRIPTION_HEADER *)(UINTN)Table;
-    if (Context->Fadt->Header.Length >= OFFSET_OF (EFI_ACPI_6_2_FIXED_ACPI_DESCRIPTION_TABLE, XDsdt) + sizeof (Context->Fadt->XDsdt)) {
-      Context->Fadt->XDsdt = (UINT64)(UINTN) Context->Dsdt;
-    }
-    Context->Fadt->Dsdt = (UINT32)(UINTN) Context->Dsdt;
 
-    Context->Fadt->Header.Checksum = 0;
-    Context->Fadt->Header.Checksum = CalculateCheckSum8 (
-      (UINT8 *) Context->Fadt,
-      Context->Fadt->Header.Length
-      );
+    Status = AcpiAllocateCopyDsdt (Context, (EFI_ACPI_DESCRIPTION_HEADER *) Data);
+    if (EFI_ERROR (Status)) {
+      return Status;
+    }
 
   } else {
-    TablePrintSignature = AcpiReadSignature (Common);
+    Status = AcpiAllocateCopyTable ((EFI_ACPI_COMMON_HEADER *) Data, 0, &NewTable);
+    if (EFI_ERROR (Status)) {
+      return Status;
+    }
+
+    TablePrintSignature = AcpiReadSignature (NewTable);
 
     DEBUG ((
       DEBUG_INFO,
       "OCA: Inserted table %.4a (%08x) (OEM %016Lx) of %u bytes into ACPI at index %u\n",
       (CHAR8 *) &TablePrintSignature,
-      Common->Signature,
-      AcpiReadOemTableId (Common),
-      Common->Length,
+      NewTable->Signature,
+      AcpiReadOemTableId (NewTable),
+      NewTable->Length,
       Context->NumberOfTables
       ));
 
-    Context->Tables[Context->NumberOfTables] = (EFI_ACPI_COMMON_HEADER *)(UINTN)Table;
+    Context->Tables[Context->NumberOfTables] = NewTable;
     ++Context->NumberOfTables;
   }
 
@@ -946,16 +1102,33 @@ AcpiNormalizeHeaders (
   IN OUT OC_ACPI_CONTEXT  *Context
   )
 {
-  UINT32  Index;
-  UINT32  TablePrintSignature;
+  EFI_STATUS              Status;
+  UINT32                  Index;
+  EFI_ACPI_COMMON_HEADER  *NewTable;
+  UINT32                  TablePrintSignature;
 
   if (Context->Dsdt != NULL) {
+    if (!AcpiIsTableWritable ((EFI_ACPI_COMMON_HEADER *) Context->Dsdt)) {
+      Status = AcpiAllocateCopyDsdt (Context, NULL);
+      if (EFI_ERROR (Status)) {
+        return;
+      }
+    }
+
     if (AcpiNormalizeTableHeaders (Context->Dsdt)) {
       DEBUG ((DEBUG_INFO, "OCA: Normalized DSDT of %u bytes headers\n", Context->Dsdt->Length));
     }
   }
 
   for (Index = 0; Index < Context->NumberOfTables; ++Index) {
+    if (!AcpiIsTableWritable (Context->Tables[Index])) {
+      Status = AcpiAllocateCopyTable (Context->Tables[Index], 0, &NewTable);
+      if (EFI_ERROR (Status)) {
+        return;
+      }
+      Context->Tables[Index] = NewTable;
+    }
+
     if (AcpiNormalizeTableHeaders ((EFI_ACPI_DESCRIPTION_HEADER *) Context->Tables[Index])) {
       TablePrintSignature = AcpiReadSignature (Context->Tables[Index]);
 
@@ -978,11 +1151,13 @@ AcpiApplyPatch (
   IN     OC_ACPI_PATCH    *Patch
   )
 {
-  UINT32  Index;
-  UINT64  CurrOemTableId;
-  UINT32  ReplaceCount;
-  UINT32  ReplaceLimit;
-  UINT32  TablePrintSignature;
+  EFI_STATUS              Status;
+  UINT32                  Index;
+  UINT64                  CurrOemTableId;
+  UINT32                  ReplaceCount;
+  UINT32                  ReplaceLimit;
+  UINT32                  TablePrintSignature;
+  EFI_ACPI_COMMON_HEADER  *NewTable;
 
   DEBUG ((DEBUG_INFO, "OCA: Applying %u byte ACPI patch skip %u, count %u\n", Patch->Size, Patch->Skip, Patch->Count));
 
@@ -995,6 +1170,13 @@ AcpiApplyPatch (
       ReplaceLimit = Context->Dsdt->Length;
     }
 
+    if (!AcpiIsTableWritable ((EFI_ACPI_COMMON_HEADER *) Context->Dsdt)) {
+      Status = AcpiAllocateCopyDsdt (Context, NULL);
+      if (EFI_ERROR (Status)) {
+        return Status;
+      }
+    }
+
     ReplaceCount = ApplyPatch (
       Patch->Find,
       Patch->Mask,
@@ -1017,17 +1199,9 @@ AcpiApplyPatch (
       ));
 
     if (ReplaceCount > 0) {
-      Context->Dsdt->Checksum = 0;
-      Context->Dsdt->Checksum = CalculateCheckSum8 (
-        (UINT8 *) Context->Dsdt,
-        Context->Dsdt->Length
-        );
+      AcpiRefreshTableChecksum (Context->Dsdt);
+
 
-      DEBUG ((
-        DEBUG_INFO,
-        "OCA: Refreshed DSDT checksum to %02x\n",
-        Context->Dsdt->Checksum
-        ));
     }
   }
 
@@ -1050,6 +1224,14 @@ AcpiApplyPatch (
         ReplaceLimit = Context->Tables[Index]->Length;
       }
 
+      if (!AcpiIsTableWritable (Context->Tables[Index])) {
+        Status = AcpiAllocateCopyTable (Context->Tables[Index], 0, &NewTable);
+        if (EFI_ERROR (Status)) {
+          return Status;
+        }
+        Context->Tables[Index] = NewTable;
+      }
+
       ReplaceCount = ApplyPatch (
         Patch->Find,
         Patch->Mask,
@@ -1078,17 +1260,7 @@ AcpiApplyPatch (
         ));
 
       if (ReplaceCount > 0 && Context->Tables[Index]->Length >= sizeof (EFI_ACPI_DESCRIPTION_HEADER)) {
-        ((EFI_ACPI_DESCRIPTION_HEADER *)Context->Tables[Index])->Checksum = 0;
-        ((EFI_ACPI_DESCRIPTION_HEADER *)Context->Tables[Index])->Checksum = CalculateCheckSum8 (
-          (UINT8 *) Context->Tables[Index],
-          Context->Tables[Index]->Length
-          );
-
-        DEBUG ((
-          DEBUG_INFO,
-          "OCA: Refreshed checksum to %02x\n",
-          ((EFI_ACPI_DESCRIPTION_HEADER *)Context->Tables[Index])->Checksum
-          ));
+        AcpiRefreshTableChecksum ((EFI_ACPI_DESCRIPTION_HEADER *) Context->Tables[Index]);
       }
     }
   }
@@ -1145,7 +1317,9 @@ AcpiRelocateRegions (
   IN OUT OC_ACPI_CONTEXT  *Context
   )
 {
-  UINT32  Index;
+  EFI_STATUS              Status;
+  UINT32                  Index;
+  EFI_ACPI_COMMON_HEADER  *NewTable;
 
   //
   // Should not be called before AcpiLoadRegions, but just in case.
@@ -1157,11 +1331,26 @@ AcpiRelocateRegions (
   }
 
   if (Context->Dsdt != NULL) {
+    if (!AcpiIsTableWritable ((EFI_ACPI_COMMON_HEADER *) Context->Dsdt)) {
+      Status = AcpiAllocateCopyDsdt (Context, NULL);
+      if (EFI_ERROR (Status)) {
+        return;
+      }
+    }
+
     AcpiRelocateTableRegions (Context, (EFI_ACPI_COMMON_HEADER *) Context->Dsdt);
   }
 
   for (Index = 0; Index < Context->NumberOfTables; ++Index) {
     if (Context->Tables[Index]->Signature == EFI_ACPI_6_2_SECONDARY_SYSTEM_DESCRIPTION_TABLE_SIGNATURE) {
+      if (!AcpiIsTableWritable (Context->Tables[Index])) {
+        Status = AcpiAllocateCopyTable (Context->Tables[Index], 0, &NewTable);
+        if (EFI_ERROR (Status)) {
+          return;
+        }
+        Context->Tables[Index] = NewTable;
+      }
+
       AcpiRelocateTableRegions (Context, Context->Tables[Index]);
     }
   }
@@ -1172,12 +1361,9 @@ AcpiFadtEnableReset (
   IN OUT OC_ACPI_CONTEXT  *Context
   )
 {
-  EFI_STATUS                                 Status;
-  EFI_PHYSICAL_ADDRESS                       Table;
-  UINT32                                     OldSize;
-  UINT32                                     RequiredSize;
-  EFI_ACPI_6_2_FIXED_ACPI_DESCRIPTION_TABLE  *Fadt;
-  UINT32                                     Index;
+  EFI_STATUS    Status;
+  UINT32        OldSize;
+  UINT32        RequiredSize;
 
   if (Context->Fadt == NULL) {
     return EFI_NOT_FOUND;
@@ -1196,39 +1382,17 @@ AcpiFadtEnableReset (
   // REF: https://github.com/acidanthera/bugtracker/issues/897
   //
 
-  if (OldSize < RequiredSize) {
-    Table = BASE_4GB - 1;
-    Status = gBS->AllocatePages (
-      AllocateMaxAddress,
-      EfiACPIMemoryNVS,
-      EFI_SIZE_TO_PAGES (RequiredSize),
-      &Table
-      );
-
+  if (OldSize < RequiredSize || !AcpiIsTableWritable ((EFI_ACPI_COMMON_HEADER *) Context->Fadt)) {
+    Status = AcpiAllocateCopyFadt (Context, OldSize < RequiredSize ? RequiredSize : 0);
     if (EFI_ERROR (Status)) {
       return Status;
     }
 
-    Fadt = (EFI_ACPI_6_2_FIXED_ACPI_DESCRIPTION_TABLE *)(UINTN) Table;
-    CopyMem (Fadt, Context->Fadt, OldSize);
-    ZeroMem (((UINT8 *) Context->Fadt) + OldSize, RequiredSize - OldSize);
-    Fadt->Header.Length = RequiredSize;
-
-    for (Index = 0; Index < Context->NumberOfTables; ++Index) {
-      //
-      // I think sometimes there are multiple FADT tables.
-      //
-      if (Context->Tables[Index]->Signature == EFI_ACPI_6_2_FIXED_ACPI_DESCRIPTION_TABLE_SIGNATURE) {
-        Context->Tables[Index] = (EFI_ACPI_COMMON_HEADER *) Fadt;
-      }
-    }
-  } else if ((Context->Fadt->Flags & EFI_ACPI_6_2_RESET_REG_SUP) == 0
+  } else if (!((Context->Fadt->Flags & EFI_ACPI_6_2_RESET_REG_SUP) == 0
     || (Context->Fadt->Flags & EFI_ACPI_6_2_SLP_BUTTON) == 0
     || (Context->Fadt->Flags & EFI_ACPI_6_2_PWR_BUTTON) != 0
     || Context->Fadt->ResetReg.Address == 0
-    || Context->Fadt->ResetReg.RegisterBitWidth != 8) {
-    Fadt = Context->Fadt;
-  } else {
+    || Context->Fadt->ResetReg.RegisterBitWidth != 8)) {
     return EFI_SUCCESS;
   }
 
@@ -1236,24 +1400,23 @@ AcpiFadtEnableReset (
   // Enable sleep button, but disable power button actions.
   // This resolves power button action in macOS on some models.
   //
-  Fadt->Flags |= EFI_ACPI_6_2_SLP_BUTTON | EFI_ACPI_6_2_RESET_REG_SUP;
-  Fadt->Flags &= ~EFI_ACPI_6_2_PWR_BUTTON;
+  Context->Fadt->Flags |= EFI_ACPI_6_2_SLP_BUTTON | EFI_ACPI_6_2_RESET_REG_SUP;
+  Context->Fadt->Flags &= ~EFI_ACPI_6_2_PWR_BUTTON;
 
-  if (Fadt->ResetReg.Address == 0 || Fadt->ResetReg.RegisterBitWidth != 8) {
+  if (Context->Fadt->ResetReg.Address == 0 || Context->Fadt->ResetReg.RegisterBitWidth != 8) {
     //
     // Resetting through port 0xCF9 is universal on Intel and AMD.
     // But may not be the case on some laptops, which use 0xB2.
     //
-    Fadt->ResetReg.AddressSpaceId    = EFI_ACPI_6_2_SYSTEM_IO;
-    Fadt->ResetReg.RegisterBitWidth  = 8;
-    Fadt->ResetReg.RegisterBitOffset = 0;
-    Fadt->ResetReg.AccessSize        = EFI_ACPI_6_2_BYTE;
-    Fadt->ResetReg.Address           = 0xCF9;
-    Fadt->ResetValue                 = 6;
+    Context->Fadt->ResetReg.AddressSpaceId    = EFI_ACPI_6_2_SYSTEM_IO;
+    Context->Fadt->ResetReg.RegisterBitWidth  = 8;
+    Context->Fadt->ResetReg.RegisterBitOffset = 0;
+    Context->Fadt->ResetReg.AccessSize        = EFI_ACPI_6_2_BYTE;
+    Context->Fadt->ResetReg.Address           = 0xCF9;
+    Context->Fadt->ResetValue                 = 6;
   }
 
-  Fadt->Header.Checksum = 0;
-  Fadt->Header.Checksum = CalculateCheckSum8 ((UINT8 *) Fadt, Fadt->Header.Length);
+  AcpiRefreshTableChecksum ((EFI_ACPI_DESCRIPTION_HEADER *) Context->Fadt);
 
   return EFI_SUCCESS;
 }
@@ -1263,13 +1426,32 @@ AcpiResetLogoStatus (
   IN OUT OC_ACPI_CONTEXT  *Context
   )
 {
-  UINT32  Index;
+  EFI_STATUS  Status;
+  UINT32      Index;
+
+  EFI_ACPI_6_2_BOOT_GRAPHICS_RESOURCE_TABLE *Bgrt;
+  EFI_ACPI_6_2_BOOT_GRAPHICS_RESOURCE_TABLE *BgrtNew;
 
   for (Index = 0; Index < Context->NumberOfTables; ++Index) {
     if (Context->Tables[Index]->Signature == EFI_ACPI_6_2_BOOT_GRAPHICS_RESOURCE_TABLE_SIGNATURE) {
       if (Context->Tables[Index]->Length >= sizeof (EFI_ACPI_6_2_BOOT_GRAPHICS_RESOURCE_TABLE)) {
-        EFI_ACPI_6_2_BOOT_GRAPHICS_RESOURCE_TABLE *Bgrt =
-          (EFI_ACPI_6_2_BOOT_GRAPHICS_RESOURCE_TABLE *)Context->Tables[Index];
+        Bgrt = (EFI_ACPI_6_2_BOOT_GRAPHICS_RESOURCE_TABLE *) Context->Tables[Index];
+
+        if (!AcpiIsTableWritable ((EFI_ACPI_COMMON_HEADER *) Bgrt)) {
+          Status = AcpiAllocateCopyTable (
+            (EFI_ACPI_COMMON_HEADER *) Bgrt,
+            0,
+            (EFI_ACPI_COMMON_HEADER **) &BgrtNew
+            );
+
+          if (EFI_ERROR (Status)) {
+            return;
+          }
+
+          Context->Tables[Index] = (EFI_ACPI_COMMON_HEADER *) BgrtNew;
+          Bgrt                   = BgrtNew;
+        }
+
         Bgrt->Status &= ~EFI_ACPI_6_2_BGRT_STATUS_DISPLAYED;
         Bgrt->Header.Checksum = 0;
         Bgrt->Header.Checksum = CalculateCheckSum8 (
@@ -1288,7 +1470,11 @@ AcpiHandleHardwareSignature (
   IN     BOOLEAN          Reset
   )
 {
+  EFI_STATUS  Status;
+  BOOLEAN     IsXFirmwareCtrl;
+
   EFI_ACPI_6_2_FIRMWARE_ACPI_CONTROL_STRUCTURE  *Facs;
+  EFI_ACPI_6_2_FIRMWARE_ACPI_CONTROL_STRUCTURE  *FacsNew;
 
   if (Context->Fadt == NULL) {
     return;
@@ -1296,8 +1482,10 @@ AcpiHandleHardwareSignature (
 
   if (Context->Fadt->Header.Length >= OFFSET_OF (EFI_ACPI_6_2_FIXED_ACPI_DESCRIPTION_TABLE, XFirmwareCtrl) + sizeof (Context->Fadt->XFirmwareCtrl)) {
     Facs = (EFI_ACPI_6_2_FIRMWARE_ACPI_CONTROL_STRUCTURE *)(UINTN) Context->Fadt->XFirmwareCtrl;
+    IsXFirmwareCtrl = TRUE;
   } else {
     Facs = NULL;
+    IsXFirmwareCtrl = FALSE;
   }
 
   if (Facs == NULL && Context->Fadt->Header.Length >= OFFSET_OF (EFI_ACPI_6_2_FIXED_ACPI_DESCRIPTION_TABLE, FirmwareCtrl) + sizeof (Context->Fadt->FirmwareCtrl)) {
@@ -1308,6 +1496,37 @@ AcpiHandleHardwareSignature (
     DEBUG ((DEBUG_INFO, "OCA: FACS signature is %X (%d)\n", Facs->Flags, Reset));
 
     if (Reset) {
+      if (!AcpiIsTableWritable ((EFI_ACPI_COMMON_HEADER *) Facs)) {
+        Status = AcpiAllocateCopyTable (
+          (EFI_ACPI_COMMON_HEADER *) Facs,
+          0,
+          (EFI_ACPI_COMMON_HEADER **) &FacsNew
+          );
+        if (EFI_ERROR (Status)) {
+          return;
+        }
+
+        //
+        // Reallocate FADT if needed.
+        //
+        if (!AcpiIsTableWritable ((EFI_ACPI_COMMON_HEADER *) Context->Fadt)) {
+          Status = AcpiAllocateCopyFadt (Context, 0);
+          if (EFI_ERROR (Status)) {
+            FreePool (FacsNew);
+            return;
+          }
+        }
+
+        if (IsXFirmwareCtrl) {
+          Context->Fadt->XFirmwareCtrl = (UINT64)(UINTN) FacsNew;
+        } else {
+          Context->Fadt->FirmwareCtrl = (UINT32)(UINTN) FacsNew;
+        }
+        AcpiRefreshTableChecksum ((EFI_ACPI_DESCRIPTION_HEADER *) Context->Fadt);
+
+        Facs = FacsNew;
+      }
+
       //
       // TODO: We might also want to unset S4BIOS_F flag in Facs->Flags.
       //