[Patch V4 18/21] UefiCpuPkg: Combine branch for non-present and leaf ParentEntry

["duntan" <dun.tan@intel.com>]

Combine 'if' condition branch for non-present and leaf Parent
Entry in PageTableLibMapInLevel. Most steps of these two condition
are the same. This commit doesn't change any functionality.

Signed-off-by: Dun Tan <dun.tan@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
---
 UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c | 83 +++++++++++++++++++++++++++++++----------------------------------------------------
 1 file changed, 31 insertions(+), 52 deletions(-)

diff --git a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
index 55a756ad90..773948349e 100644
--- a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
+++ b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
@@ -348,68 +348,45 @@ PageTableLibMapInLevel (
   // ParentPagingEntry ONLY is deferenced for checking Present and MustBeOne bits
   // when Modify is FALSE.
   //
-
-  if (ParentPagingEntry->Pce.Present == 0) {
-    //
-    // [LinearAddress, LinearAddress + Length] contains non-present range.
-    //
-    Status = IsAttributesAndMaskValidForNonPresentEntry (Attribute, Mask);
-    if (RETURN_ERROR (Status)) {
-      return Status;
-    }
-
+  if ((ParentPagingEntry->Pce.Present == 0) || IsPle (ParentPagingEntry, Level + 1)) {
     //
-    // Check the attribute in ParentPagingEntry is equal to attribute calculated by input Attribue and Mask.
-    //
-    PleBAttribute.Uint64 = PageTableLibGetPleBMapAttribute (&ParentPagingEntry->PleB, ParentAttribute);
-    if ((IA32_MAP_ATTRIBUTE_ATTRIBUTES (&PleBAttribute) & IA32_MAP_ATTRIBUTE_ATTRIBUTES (Mask))
-        == (IA32_MAP_ATTRIBUTE_ATTRIBUTES (Attribute) & IA32_MAP_ATTRIBUTE_ATTRIBUTES (Mask)))
-    {
-      return RETURN_SUCCESS;
-    }
-
-    //
-    // The parent entry is CR3 or PML5E/PML4E/PDPTE/PDE.
+    // When ParentPagingEntry is non-present, parent entry is CR3 or PML5E/PML4E/PDPTE/PDE.
     // It does NOT point to an existing page directory.
+    // When ParentPagingEntry is present, parent entry is leaf PDPTE_1G or PDE_2M. Split to 2M or 4K pages.
+    // Note: it's impossible the parent entry is a PTE_4K.
     //
-    ASSERT (Buffer == NULL || *BufferSize >= SIZE_4KB);
-    CreateNew    = TRUE;
-    *BufferSize -= SIZE_4KB;
+    OneOfPagingEntry.Pnle.Uint64 = 0;
+    PleBAttribute.Uint64         = PageTableLibGetPleBMapAttribute (&ParentPagingEntry->PleB, ParentAttribute);
 
-    if (Modify) {
-      ParentPagingEntry->Uintn = (UINTN)Buffer + *BufferSize;
-      ZeroMem ((VOID *)ParentPagingEntry->Uintn, SIZE_4KB);
+    if (ParentPagingEntry->Pce.Present == 0) {
       //
-      // Set default attribute bits for PML5E/PML4E/PDPTE/PDE.
+      // [LinearAddress, LinearAddress + Length] contains non-present range.
       //
-      PageTableLibSetPnle (&ParentPagingEntry->Pnle, &NopAttribute, &AllOneMask);
+      Status = IsAttributesAndMaskValidForNonPresentEntry (Attribute, Mask);
+      if (RETURN_ERROR (Status)) {
+        return Status;
+      }
     } else {
-      //
-      // Just make sure Present and MustBeZero (PageSize) bits are accurate.
-      //
-      OneOfPagingEntry.Pnle.Uint64 = 0;
+      PageTableLibSetPle (Level, &OneOfPagingEntry, 0, &PleBAttribute, &AllOneMask);
     }
-  } else if (IsPle (ParentPagingEntry, Level + 1)) {
-    //
-    // The parent entry is a PDPTE_1G or PDE_2M. Split to 2M or 4K pages.
-    // Note: it's impossible the parent entry is a PTE_4K.
-    //
+
     //
-    // Use NOP attributes as the attribute of grand-parents because CPU will consider
-    // the actual attributes of grand-parents when determing the memory type.
+    // Check if the attribute, the physical address calculated by ParentPagingEntry is equal to
+    // the attribute, the physical address calculated by input Attribue and Mask.
     //
-    PleBAttribute.Uint64 = PageTableLibGetPleBMapAttribute (&ParentPagingEntry->PleB, ParentAttribute);
     if ((IA32_MAP_ATTRIBUTE_ATTRIBUTES (&PleBAttribute) & IA32_MAP_ATTRIBUTE_ATTRIBUTES (Mask))
         == (IA32_MAP_ATTRIBUTE_ATTRIBUTES (Attribute) & IA32_MAP_ATTRIBUTE_ATTRIBUTES (Mask)))
     {
-      //
-      // This function is called when the memory length is less than the region length of the parent level.
-      // No need to split the page when the attributes equal.
-      //
       if ((Mask->Bits.PageTableBaseAddressLow == 0) && (Mask->Bits.PageTableBaseAddressHigh == 0)) {
         return RETURN_SUCCESS;
       }
 
+      //
+      // Non-present entry won't reach there since:
+      // 1.When map non-present entry to present, the attribute must be different.
+      // 2.When still map non-present entry to non-present, PageTableBaseAddressLow and High in Mask must be 0.
+      //
+      ASSERT (ParentPagingEntry->Pce.Present == 1);
       PhysicalAddrInEntry = IA32_MAP_ATTRIBUTE_PAGE_TABLE_BASE_ADDRESS (&PleBAttribute) + PagingEntryIndex * RegionLength;
       PhysicalAddrInAttr  = (IA32_MAP_ATTRIBUTE_PAGE_TABLE_BASE_ADDRESS (Attribute) + Offset) & (~RegionMask);
       if (PhysicalAddrInEntry == PhysicalAddrInAttr) {
@@ -420,17 +397,19 @@ PageTableLibMapInLevel (
     ASSERT (Buffer == NULL || *BufferSize >= SIZE_4KB);
     CreateNew    = TRUE;
     *BufferSize -= SIZE_4KB;
-    PageTableLibSetPle (Level, &OneOfPagingEntry, 0, &PleBAttribute, &AllOneMask);
+
     if (Modify) {
-      //
-      // Create 512 child-level entries that map to 2M/4K.
-      //
       PagingEntry = (IA32_PAGING_ENTRY *)((UINTN)Buffer + *BufferSize);
       ZeroMem (PagingEntry, SIZE_4KB);
 
-      for (SubOffset = 0, Index = 0; Index < 512; Index++) {
-        PagingEntry[Index].Uint64 = OneOfPagingEntry.Uint64 + SubOffset;
-        SubOffset                += RegionLength;
+      if (ParentPagingEntry->Pce.Present) {
+        //
+        // Create 512 child-level entries that map to 2M/4K.
+        //
+        for (SubOffset = 0, Index = 0; Index < 512; Index++) {
+          PagingEntry[Index].Uint64 = OneOfPagingEntry.Uint64 + SubOffset;
+          SubOffset                += RegionLength;
+        }
       }
 
       //
-- 
2.31.1.windows.1