Modify CpuPageTableLib code to enable PAE paging.
In PageTableMap() API:
When creating new PAE page table, after creating page table,
set all MustBeZero fields of 4 PDPTE to 0. The MustBeZero
fields are treated as RW and other attributes by the common
map logic. So they might be set to 1.
When updating exsiting PAE page table, the special steps are:
1.Prepare 4K-aligned 32bytes memory in stack for 4 temp PDPTE.
2.Copy original 4 PDPTE to the 4 temp PDPTE and set the RW,
  UserSupervisor to 1 and set Nx of 4 temp PDPTE to 0.
4.After updating the page table, set the MustBeZero fields of
  4 temp PDPTE to 0.
5.Copy the temp PDPTE to original PDPTE.

In PageTableParse() API, also create 4 temp PDPTE in stack.
Copy original 4 PDPTE to the 4 temp PDPTE. Then set the RW,
UserSupervisor to 1 and set Nx of 4 temp PDPTE to 0. Finally
use the address of temp PDPTE as the page table address.

Signed-off-by: Dun Tan <dun....@intel.com>
Cc: Eric Dong <eric.d...@intel.com>
Cc: Ray Ni <ray...@intel.com>
Cc: Rahul Kumar <rahul1.ku...@intel.com>
Cc: Gerd Hoffmann <kra...@redhat.com>
---
 UefiCpuPkg/Library/CpuPageTableLib/CpuPageTable.h      | 10 +++++++---
 UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c   | 53 
++++++++++++++++++++++++++++++++++++++++++++++++-----
 UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableParse.c | 25 
+++++++++++++++++++++----
 3 files changed, 76 insertions(+), 12 deletions(-)

diff --git a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTable.h 
b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTable.h
index 2c67ecb469..521d56c148 100644
--- a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTable.h
+++ b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTable.h
@@ -15,11 +15,14 @@
 #include <Library/DebugLib.h>
 #include <Library/CpuPageTableLib.h>
 
-#define IA32_PE_BASE_ADDRESS_MASK_40  0xFFFFFFFFFF000ull
-#define IA32_PE_BASE_ADDRESS_MASK_39  0xFFFFFFFFFE000ull
+#define IA32_PE_BASE_ADDRESS_MASK_40         0xFFFFFFFFFF000ull
+#define IA32_PE_BASE_ADDRESS_MASK_39         0xFFFFFFFFFE000ull
+#define IA32_PE_BASE_ADDRESS_MASK_PAE_PDPTE  0xFFFFFFFFFFFE0ull
 
 #define REGION_LENGTH(l)  LShiftU64 (1, (l) * 9 + 3)
 
+#define MAX_PAE_PDPTE_NUM  4
+
 typedef enum {
   Pte   = 1,
   Pde   = 2,
@@ -60,7 +63,8 @@ typedef union {
   UINT64    Uint64;
 } IA32_PAGE_NON_LEAF_ENTRY;
 
-#define IA32_PNLE_PAGE_TABLE_BASE_ADDRESS(pa)  ((pa)->Uint64 & 
IA32_PE_BASE_ADDRESS_MASK_40)
+#define IA32_PNLE_PAGE_TABLE_BASE_ADDRESS(pa)       ((pa)->Uint64 & 
IA32_PE_BASE_ADDRESS_MASK_40)
+#define IA32_PAE_PDPTE_PAGE_TABLE_BASE_ADDRESS(pa)  ((pa)->Uint64 & 
IA32_PE_BASE_ADDRESS_MASK_PAE_PDPTE)
 
 ///
 /// Format of a PML5 Entry (PML5E) that References a PML4 Table
diff --git a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c 
b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
index 773948349e..8769e45f25 100644
--- a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
+++ b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
@@ -661,15 +661,17 @@ PageTableMap (
   IA32_PAGE_LEVEL     MaxLeafLevel;
   IA32_MAP_ATTRIBUTE  ParentAttribute;
   BOOLEAN             LocalIsModified;
+  UINTN               Index;
+  IA32_PAGING_ENTRY   *PagingEntry;
+  UINT8               BufferInStack[SIZE_4KB - 1 + MAX_PAE_PDPTE_NUM * sizeof 
(IA32_PAGING_ENTRY)];
 
   if (Length == 0) {
     return RETURN_SUCCESS;
   }
 
-  if ((PagingMode == Paging32bit) || (PagingMode == PagingPae) || (PagingMode 
>= PagingModeMax)) {
+  if ((PagingMode == Paging32bit) || (PagingMode >= PagingModeMax)) {
     //
     // 32bit paging is never supported.
-    // PAE paging will be supported later.
     //
     return RETURN_UNSUPPORTED;
   }
@@ -706,17 +708,32 @@ PageTableMap (
 
   MaxLeafLevel     = (IA32_PAGE_LEVEL)(UINT8)PagingMode;
   MaxLevel         = (IA32_PAGE_LEVEL)(UINT8)(PagingMode >> 8);
-  MaxLinearAddress = LShiftU64 (1, 12 + MaxLevel * 9);
+  MaxLinearAddress = (PagingMode == PagingPae) ? LShiftU64 (1, 32) : LShiftU64 
(1, 12 + MaxLevel * 9);
 
   if ((LinearAddress > MaxLinearAddress) || (Length > MaxLinearAddress - 
LinearAddress)) {
     //
-    // Maximum linear address is (1 << 48) or (1 << 57)
+    // Maximum linear address is (1 << 32), (1 << 48) or (1 << 57)
     //
     return RETURN_INVALID_PARAMETER;
   }
 
   TopPagingEntry.Uintn = *PageTable;
   if (TopPagingEntry.Uintn != 0) {
+    if (PagingMode == PagingPae) {
+      //
+      // Create 4 temporary PDPTE at a 4k-aligned address.
+      // Copy the original PDPTE content and set ReadWrite, UserSupervisor to 
1, set Nx to 0.
+      //
+      TopPagingEntry.Uintn = ALIGN_VALUE ((UINTN)BufferInStack, BASE_4KB);
+      PagingEntry          = (IA32_PAGING_ENTRY *)(TopPagingEntry.Uintn);
+      CopyMem (PagingEntry, (VOID *)(*PageTable), MAX_PAE_PDPTE_NUM * sizeof 
(IA32_PAGING_ENTRY));
+      for (Index = 0; Index < MAX_PAE_PDPTE_NUM; Index++) {
+        PagingEntry[Index].Pnle.Bits.ReadWrite      = 1;
+        PagingEntry[Index].Pnle.Bits.UserSupervisor = 1;
+        PagingEntry[Index].Pnle.Bits.Nx             = 0;
+      }
+    }
+
     TopPagingEntry.Pce.Present        = 1;
     TopPagingEntry.Pce.ReadWrite      = 1;
     TopPagingEntry.Pce.UserSupervisor = 1;
@@ -792,7 +809,33 @@ PageTableMap (
   }
 
   if (!RETURN_ERROR (Status)) {
-    *PageTable = (UINTN)(TopPagingEntry.Uintn & IA32_PE_BASE_ADDRESS_MASK_40);
+    PagingEntry = (IA32_PAGING_ENTRY *)(UINTN)(TopPagingEntry.Uintn & 
IA32_PE_BASE_ADDRESS_MASK_40);
+
+    if (PagingMode == PagingPae) {
+      //
+      // These MustBeZero fields are treated as RW and other attributes by the 
common map logic. So they might be set to 1.
+      //
+      for (Index = 0; Index < MAX_PAE_PDPTE_NUM; Index++) {
+        PagingEntry[Index].PdptePae.Bits.MustBeZero  = 0;
+        PagingEntry[Index].PdptePae.Bits.MustBeZero2 = 0;
+        PagingEntry[Index].PdptePae.Bits.MustBeZero3 = 0;
+      }
+
+      if (*PageTable != 0) {
+        //
+        // Copy temp PDPTE to original PDPTE.
+        //
+        CopyMem ((VOID *)(*PageTable), PagingEntry, MAX_PAE_PDPTE_NUM * sizeof 
(IA32_PAGING_ENTRY));
+      }
+    }
+
+    if (*PageTable == 0) {
+      //
+      // Do not assign the *PageTable when it's an existing page table.
+      // If it's an existing PAE page table, PagingEntry is the temp buffer in 
stack.
+      //
+      *PageTable = (UINTN)PagingEntry;
+    }
   }
 
   return Status;
diff --git a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableParse.c 
b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableParse.c
index 65490751ab..f6d7b9bb4c 100644
--- a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableParse.c
+++ b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableParse.c
@@ -158,6 +158,7 @@ VOID
 PageTableLibParsePnle (
   IN     UINT64              PageTableBaseAddress,
   IN     UINTN               Level,
+  IN     UINTN               MaxLevel,
   IN     UINT64              RegionStart,
   IN     IA32_MAP_ATTRIBUTE  *ParentMapAttribute,
   IN OUT IA32_MAP_ENTRY      *Map,
@@ -171,13 +172,15 @@ PageTableLibParsePnle (
   UINTN               Index;
   IA32_MAP_ATTRIBUTE  MapAttribute;
   UINT64              RegionLength;
+  UINTN               PagingEntryNumber;
 
   ASSERT (OneEntry != NULL);
 
-  PagingEntry  = (IA32_PAGING_ENTRY *)(UINTN)PageTableBaseAddress;
-  RegionLength = REGION_LENGTH (Level);
+  PagingEntry       = (IA32_PAGING_ENTRY *)(UINTN)PageTableBaseAddress;
+  RegionLength      = REGION_LENGTH (Level);
+  PagingEntryNumber = ((MaxLevel == 3) && (Level == 3)) ? MAX_PAE_PDPTE_NUM : 
512;
 
-  for (Index = 0; Index < 512; Index++, RegionStart += RegionLength) {
+  for (Index = 0; Index < PagingEntryNumber; Index++, RegionStart += 
RegionLength) {
     if (PagingEntry[Index].Pce.Present == 0) {
       continue;
     }
@@ -228,6 +231,7 @@ PageTableLibParsePnle (
       PageTableLibParsePnle (
         IA32_PNLE_PAGE_TABLE_BASE_ADDRESS (&PagingEntry[Index].Pnle),
         Level - 1,
+        MaxLevel,
         RegionStart,
         &MapAttribute,
         Map,
@@ -269,6 +273,8 @@ PageTableParse (
   IA32_MAP_ENTRY      *LastEntry;
   IA32_MAP_ENTRY      OneEntry;
   UINTN               MaxLevel;
+  UINTN               Index;
+  IA32_PAGING_ENTRY   BufferInStack[MAX_PAE_PDPTE_NUM];
 
   if ((PagingMode == Paging32bit) || (PagingMode >= PagingModeMax)) {
     //
@@ -290,6 +296,17 @@ PageTableParse (
     return RETURN_SUCCESS;
   }
 
+  if (PagingMode == PagingPae) {
+    CopyMem (BufferInStack, (VOID *)PageTable, sizeof (BufferInStack));
+    for (Index = 0; Index < MAX_PAE_PDPTE_NUM; Index++) {
+      BufferInStack[Index].Pnle.Bits.ReadWrite      = 1;
+      BufferInStack[Index].Pnle.Bits.UserSupervisor = 1;
+      BufferInStack[Index].Pnle.Bits.Nx             = 0;
+    }
+
+    PageTable = (UINTN)BufferInStack;
+  }
+
   //
   // Page table layout is as below:
   //
@@ -319,7 +336,7 @@ PageTableParse (
   MapCapacity = *MapCount;
   *MapCount   = 0;
   LastEntry   = NULL;
-  PageTableLibParsePnle ((UINT64)PageTable, MaxLevel, 0, &NopAttribute, Map, 
MapCount, MapCapacity, &LastEntry, &OneEntry);
+  PageTableLibParsePnle ((UINT64)PageTable, MaxLevel, MaxLevel, 0, 
&NopAttribute, Map, MapCount, MapCapacity, &LastEntry, &OneEntry);
 
   if (*MapCount > MapCapacity) {
     return RETURN_BUFFER_TOO_SMALL;
-- 
2.31.1.windows.1



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