[PATCH] UefiCpuPkg/PiSmmCpu: Enable 5L paging only when phy addr line > 48

["Ni, Ray" <ray.ni@intel.com>]

Today's behavior is to enable 5l paging when CPU supports it
(CPUID[7,0].ECX.BIT[16] is set).

The patch changes the behavior to enable 5l paging when two
conditions are both met:
1. CPU supports it;
2. The max physical address bits is bigger than 48.

Because 4-level paging can support to address physical address up to
2^48 - 1, there is no need to enable 5-level paging with max
physical address bits <= 48.

Signed-off-by: Ray Ni <ray.ni@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Eric Dong <Eric.dong@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c     | 57 +++++++++++++--------
 UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm |  4 +-
 2 files changed, 39 insertions(+), 22 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
index 733d107efd..e5c4788c13 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
@@ -16,8 +16,8 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 LIST_ENTRY                          mPagePool = INITIALIZE_LIST_HEAD_VARIABLE (mPagePool);
 BOOLEAN                             m1GPageTableSupport = FALSE;
 BOOLEAN                             mCpuSmmRestrictedMemoryAccess;
-BOOLEAN                             m5LevelPagingSupport;
-X86_ASSEMBLY_PATCH_LABEL            gPatch5LevelPagingSupport;
+BOOLEAN                             m5LevelPagingNeeded;
+X86_ASSEMBLY_PATCH_LABEL            gPatch5LevelPagingNeeded;
 
 /**
   Disable CET.
@@ -63,28 +63,45 @@ Is1GPageSupport (
 }
 
 /**
-  Check if 5-level paging is supported by processor or not.
-
-  @retval TRUE   5-level paging is supported.
-  @retval FALSE  5-level paging is not supported.
+  The routine returns TRUE when CPU supports it (CPUID[7,0].ECX.BIT[16] is set) and
+  the max physical address bits is bigger than 48. Because 4-level paging can support
+  to address physical address up to 2^48 - 1, there is no need to enable 5-level paging
+  with max physical address bits <= 48.
 
+  @retval TRUE  5-level paging enabling is needed.
+  @retval FALSE 5-level paging enabling is not needed.
 **/
 BOOLEAN
-Is5LevelPagingSupport (
+Is5LevelPagingNeeded (
   VOID
   )
 {
-  CPUID_STRUCTURED_EXTENDED_FEATURE_FLAGS_ECX EcxFlags;
+  CPUID_VIR_PHY_ADDRESS_SIZE_EAX              VirPhyAddressSize;
+  CPUID_STRUCTURED_EXTENDED_FEATURE_FLAGS_ECX ExtFeatureEcx;
+  UINT32                                      MaxExtendedFunctionId;
 
+  AsmCpuid (CPUID_EXTENDED_FUNCTION, &MaxExtendedFunctionId, NULL, NULL, NULL);
+  if (MaxExtendedFunctionId >= CPUID_VIR_PHY_ADDRESS_SIZE) {
+    AsmCpuid (CPUID_VIR_PHY_ADDRESS_SIZE, &VirPhyAddressSize.Uint32, NULL, NULL, NULL);
+  } else {
+    VirPhyAddressSize.Bits.PhysicalAddressBits = 36;
+  }
   AsmCpuidEx (
     CPUID_STRUCTURED_EXTENDED_FEATURE_FLAGS,
     CPUID_STRUCTURED_EXTENDED_FEATURE_FLAGS_SUB_LEAF_INFO,
-    NULL,
-    NULL,
-    &EcxFlags.Uint32,
-    NULL
+    NULL, NULL, &ExtFeatureEcx.Uint32, NULL
     );
-  return (BOOLEAN) (EcxFlags.Bits.FiveLevelPage != 0);
+  DEBUG ((
+    DEBUG_INFO, "PhysicalAddressBits = %d, 5LPageTable = %d.\n",
+    VirPhyAddressSize.Bits.PhysicalAddressBits, ExtFeatureEcx.Bits.FiveLevelPage
+    ));
+
+  if (VirPhyAddressSize.Bits.PhysicalAddressBits > 4 * 9 + 12) {
+    ASSERT (ExtFeatureEcx.Bits.FiveLevelPage == 1);
+    return TRUE;
+  } else {
+    return FALSE;
+  }
 }
 
 /**
@@ -190,7 +207,7 @@ SetStaticPageTable (
   //  when 5-Level Paging is disabled.
   //
   ASSERT (mPhysicalAddressBits <= 52);
-  if (!m5LevelPagingSupport && mPhysicalAddressBits > 48) {
+  if (!m5LevelPagingNeeded && mPhysicalAddressBits > 48) {
     mPhysicalAddressBits = 48;
   }
 
@@ -217,7 +234,7 @@ SetStaticPageTable (
 
   PageMapLevel4Entry = PageMap;
   PageMapLevel5Entry = NULL;
-  if (m5LevelPagingSupport) {
+  if (m5LevelPagingNeeded) {
     //
     // By architecture only one PageMapLevel5 exists - so lets allocate storage for it.
     //
@@ -233,7 +250,7 @@ SetStaticPageTable (
     // So lets allocate space for them and fill them in in the IndexOfPml4Entries loop.
     // When 5-Level Paging is disabled, below allocation happens only once.
     //
-    if (m5LevelPagingSupport) {
+    if (m5LevelPagingNeeded) {
       PageMapLevel4Entry = (UINT64 *) ((*PageMapLevel5Entry) & ~mAddressEncMask & gPhyMask);
       if (PageMapLevel4Entry == NULL) {
         PageMapLevel4Entry = AllocatePageTableMemory (1);
@@ -336,10 +353,10 @@ SmmInitPageTable (
 
   mCpuSmmRestrictedMemoryAccess = PcdGetBool (PcdCpuSmmRestrictedMemoryAccess);
   m1GPageTableSupport           = Is1GPageSupport ();
-  m5LevelPagingSupport          = Is5LevelPagingSupport ();
+  m5LevelPagingNeeded           = Is5LevelPagingNeeded ();
   mPhysicalAddressBits          = CalculateMaximumSupportAddress ();
-  PatchInstructionX86 (gPatch5LevelPagingSupport, m5LevelPagingSupport, 1);
-  DEBUG ((DEBUG_INFO, "5LevelPaging Support            - %d\n", m5LevelPagingSupport));
+  PatchInstructionX86 (gPatch5LevelPagingNeeded, m5LevelPagingNeeded, 1);
+  DEBUG ((DEBUG_INFO, "5LevelPaging Needed             - %d\n", m5LevelPagingNeeded));
   DEBUG ((DEBUG_INFO, "1GPageTable Support             - %d\n", m1GPageTableSupport));
   DEBUG ((DEBUG_INFO, "PcdCpuSmmRestrictedMemoryAccess - %d\n", mCpuSmmRestrictedMemoryAccess));
   DEBUG ((DEBUG_INFO, "PhysicalAddressBits             - %d\n", mPhysicalAddressBits));
@@ -370,7 +387,7 @@ SmmInitPageTable (
   SetSubEntriesNum (Pml4Entry, 3);
   PTEntry = Pml4Entry;
 
-  if (m5LevelPagingSupport) {
+  if (m5LevelPagingNeeded) {
     //
     // Fill PML5 entry
     //
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
index 271492a9d7..db06d22d51 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
@@ -69,7 +69,7 @@ extern ASM_PFX(mXdSupported)
 global ASM_PFX(gPatchXdSupported)
 global ASM_PFX(gPatchSmiStack)
 global ASM_PFX(gPatchSmiCr3)
-global ASM_PFX(gPatch5LevelPagingSupport)
+global ASM_PFX(gPatch5LevelPagingNeeded)
 global ASM_PFX(gcSmiHandlerTemplate)
 global ASM_PFX(gcSmiHandlerSize)
 
@@ -127,7 +127,7 @@ ASM_PFX(gPatchSmiCr3):
     mov     eax, 0x668                   ; as cr4.PGE is not set here, refresh cr3
 
     mov     cl, strict byte 0            ; source operand will be patched
-ASM_PFX(gPatch5LevelPagingSupport):
+ASM_PFX(gPatch5LevelPagingNeeded):
     cmp     cl, 0
     je      SkipEnable5LevelPaging
     ;
-- 
2.21.0.windows.1