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[edk2-devel] [PATCH 2/5] UefiCpuPkg/PiSmmCpu: Use new PCD PcdCpuSmmRestrictedMemoryAccess

Ni, Ray posted 5 patches 6 years, 5 months ago
[edk2-devel] [PATCH 2/5] UefiCpuPkg/PiSmmCpu: Use new PCD PcdCpuSmmRestrictedMemoryAccess
Posted by Ni, Ray 6 years, 5 months ago 
The patch changes PiSmmCpu driver to consume PCD
PcdCpuSmmRestrictedMemoryAccess.
Because the behavior controlled by PcdCpuSmmStaticPageTable in
original code is not changed after switching to
PcdCpuSmmRestrictedMemoryAccess.

The functionality is not impacted by this patch.

Signed-off-by: Ray Ni <ray.ni@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf |  4 +-
 UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c      | 52 ++++++++++++--------
 2 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
index da0308c47f..b12b2691f8 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
@@ -133,7 +133,6 @@ [Pcd]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuHotPlugDataAddress               ## SOMETIMES_PRODUCES
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmCodeAccessCheckEnable         ## CONSUMES
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode                      ## CONSUMES
-  gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStaticPageTable               ## CONSUMES
   gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmShadowStackSize               ## SOMETIMES_CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiS3Enable                   ## CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask    ## CONSUMES
@@ -141,6 +140,9 @@ [Pcd]
   gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPropertyMask               ## CONSUMES
   gEfiMdePkgTokenSpaceGuid.PcdControlFlowEnforcementPropertyMask        ## CONSUMES
 
+[Pcd.X64]
+  gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmRestrictedMemoryAccess        ## CONSUMES
+
 [Depex]
   gEfiMpServiceProtocolGuid
 
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
index d60c404a3d..7516f35055 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
@@ -15,7 +15,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 
 LIST_ENTRY                          mPagePool = INITIALIZE_LIST_HEAD_VARIABLE (mPagePool);
 BOOLEAN                             m1GPageTableSupport = FALSE;
-BOOLEAN                             mCpuSmmStaticPageTable;
+BOOLEAN                             mCpuSmmRestrictedMemoryAccess;
 BOOLEAN                             m5LevelPagingSupport;
 X86_ASSEMBLY_PATCH_LABEL            gPatch5LevelPagingSupport;
 
@@ -334,15 +334,15 @@ SmmInitPageTable (
   //
   InitializeSpinLock (mPFLock);
 
-  mCpuSmmStaticPageTable = PcdGetBool (PcdCpuSmmStaticPageTable);
-  m1GPageTableSupport    = Is1GPageSupport ();
-  m5LevelPagingSupport   = Is5LevelPagingSupport ();
-  mPhysicalAddressBits   = CalculateMaximumSupportAddress ();
+  mCpuSmmRestrictedMemoryAccess = PcdGetBool (PcdCpuSmmRestrictedMemoryAccess);
+  m1GPageTableSupport           = Is1GPageSupport ();
+  m5LevelPagingSupport          = Is5LevelPagingSupport ();
+  mPhysicalAddressBits          = CalculateMaximumSupportAddress ();
   PatchInstructionX86 (gPatch5LevelPagingSupport, m5LevelPagingSupport, 1);
-  DEBUG ((DEBUG_INFO, "5LevelPaging Support     - %d\n", m5LevelPagingSupport));
-  DEBUG ((DEBUG_INFO, "1GPageTable Support      - %d\n", m1GPageTableSupport));
-  DEBUG ((DEBUG_INFO, "PcdCpuSmmStaticPageTable - %d\n", mCpuSmmStaticPageTable));
-  DEBUG ((DEBUG_INFO, "PhysicalAddressBits      - %d\n", mPhysicalAddressBits));
+  DEBUG ((DEBUG_INFO, "5LevelPaging Support            - %d\n", m5LevelPagingSupport));
+  DEBUG ((DEBUG_INFO, "1GPageTable Support             - %d\n", m1GPageTableSupport));
+  DEBUG ((DEBUG_INFO, "PcdCpuSmmRestrictedMemoryAccess - %d\n", mCpuSmmRestrictedMemoryAccess));
+  DEBUG ((DEBUG_INFO, "PhysicalAddressBits             - %d\n", mPhysicalAddressBits));
   //
   // Generate PAE page table for the first 4GB memory space
   //
@@ -385,7 +385,11 @@ SmmInitPageTable (
     PTEntry = Pml5Entry;
   }
 
-  if (mCpuSmmStaticPageTable) {
+  if (mCpuSmmRestrictedMemoryAccess) {
+    //
+    // When access to non-SMRAM memory is restricted, create page table
+    // that covers all memory space.
+    //
     SetStaticPageTable ((UINTN)PTEntry);
   } else {
     //
@@ -972,7 +976,7 @@ SmiPFHandler (
 
   PFAddress = AsmReadCr2 ();
 
-  if (mCpuSmmStaticPageTable && (PFAddress >= LShiftU64 (1, (mPhysicalAddressBits - 1)))) {
+  if (mCpuSmmRestrictedMemoryAccess && (PFAddress >= LShiftU64 (1, (mPhysicalAddressBits - 1)))) {
     DumpCpuContext (InterruptType, SystemContext);
     DEBUG ((DEBUG_ERROR, "Do not support address 0x%lx by processor!\n", PFAddress));
     CpuDeadLoop ();
@@ -1049,7 +1053,7 @@ SmiPFHandler (
       goto Exit;
     }
 
-    if (mCpuSmmStaticPageTable && IsSmmCommBufferForbiddenAddress (PFAddress)) {
+    if (mCpuSmmRestrictedMemoryAccess && IsSmmCommBufferForbiddenAddress (PFAddress)) {
       DumpCpuContext (InterruptType, SystemContext);
       DEBUG ((DEBUG_ERROR, "Access SMM communication forbidden address (0x%lx)!\n", PFAddress));
       DEBUG_CODE (
@@ -1100,26 +1104,26 @@ SetPageTableAttributes (
   Enable5LevelPaging = (BOOLEAN) (Cr4.Bits.LA57 == 1);
 
   //
-  // Don't do this if
-  //  - no static page table; or
+  // Don't mark page table memory as read-only if
+  //  - no restriction on access to non-SMRAM memory; or
   //  - SMM heap guard feature enabled; or
   //      BIT2: SMM page guard enabled
   //      BIT3: SMM pool guard enabled
   //  - SMM profile feature enabled
   //
-  if (!mCpuSmmStaticPageTable ||
+  if (!mCpuSmmRestrictedMemoryAccess ||
       ((PcdGet8 (PcdHeapGuardPropertyMask) & (BIT3 | BIT2)) != 0) ||
       FeaturePcdGet (PcdCpuSmmProfileEnable)) {
     //
-    // Static paging and heap guard could not be enabled at the same time.
+    // Restriction on access to non-SMRAM memory and heap guard could not be enabled at the same time.
     //
-    ASSERT (!(mCpuSmmStaticPageTable &&
+    ASSERT (!(mCpuSmmRestrictedMemoryAccess &&
               (PcdGet8 (PcdHeapGuardPropertyMask) & (BIT3 | BIT2)) != 0));
 
     //
-    // Static paging and SMM profile could not be enabled at the same time.
+    // Restriction on access to non-SMRAM memory and SMM profile could not be enabled at the same time.
     //
-    ASSERT (!(mCpuSmmStaticPageTable && FeaturePcdGet (PcdCpuSmmProfileEnable)));
+    ASSERT (!(mCpuSmmRestrictedMemoryAccess && FeaturePcdGet (PcdCpuSmmProfileEnable)));
     return ;
   }
 
@@ -1223,7 +1227,10 @@ SaveCr2 (
   OUT UINTN  *Cr2
   )
 {
-  if (!mCpuSmmStaticPageTable) {
+  if (!mCpuSmmRestrictedMemoryAccess) {
+    //
+    // On-demand paging is enabled when access to non-SMRAM is not restricted.
+    //
     *Cr2 = AsmReadCr2 ();
   }
 }
@@ -1238,7 +1245,10 @@ RestoreCr2 (
   IN UINTN  Cr2
   )
 {
-  if (!mCpuSmmStaticPageTable) {
+  if (!mCpuSmmRestrictedMemoryAccess) {
+    //
+    // On-demand paging is enabled when access to non-SMRAM is not restricted.
+    //
     AsmWriteCr2 (Cr2);
   }
 }
-- 
2.21.0.windows.1


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Re: [edk2-devel] [PATCH 2/5] UefiCpuPkg/PiSmmCpu: Use new PCD PcdCpuSmmRestrictedMemoryAccess
Posted by Dong, Eric 6 years, 5 months ago 
Reviewed-by: Eric Dong <eric.dong@intel.com>

> -----Original Message-----
> From: Ni, Ray
> Sent: Monday, August 26, 2019 6:45 AM
> To: devel@edk2.groups.io
> Cc: Dong, Eric <eric.dong@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>;
> Laszlo Ersek <lersek@redhat.com>
> Subject: [PATCH 2/5] UefiCpuPkg/PiSmmCpu: Use new PCD
> PcdCpuSmmRestrictedMemoryAccess
> 
> The patch changes PiSmmCpu driver to consume PCD
> PcdCpuSmmRestrictedMemoryAccess.
> Because the behavior controlled by PcdCpuSmmStaticPageTable in original
> code is not changed after switching to PcdCpuSmmRestrictedMemoryAccess.
> 
> The functionality is not impacted by this patch.
> 
> Signed-off-by: Ray Ni <ray.ni@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf |  4 +-
>  UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c      | 52 ++++++++++++--------
>  2 files changed, 34 insertions(+), 22 deletions(-)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
> b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
> index da0308c47f..b12b2691f8 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
> @@ -133,7 +133,6 @@ [Pcd]
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuHotPlugDataAddress               ##
> SOMETIMES_PRODUCES
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmCodeAccessCheckEnable         ##
> CONSUMES
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode                      ##
> CONSUMES
> -  gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStaticPageTable               ##
> CONSUMES
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmShadowStackSize               ##
> SOMETIMES_CONSUMES
>    gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiS3Enable                   ##
> CONSUMES
> 
> gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask
> ## CONSUMES
> @@ -141,6 +140,9 @@ [Pcd]
>    gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPropertyMask               ##
> CONSUMES
>    gEfiMdePkgTokenSpaceGuid.PcdControlFlowEnforcementPropertyMask
> ## CONSUMES
> 
> +[Pcd.X64]
> +  gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmRestrictedMemoryAccess        ##
> CONSUMES
> +
>  [Depex]
>    gEfiMpServiceProtocolGuid
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> index d60c404a3d..7516f35055 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> @@ -15,7 +15,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
> 
>  LIST_ENTRY                          mPagePool = INITIALIZE_LIST_HEAD_VARIABLE
> (mPagePool);
>  BOOLEAN                             m1GPageTableSupport = FALSE;
> -BOOLEAN                             mCpuSmmStaticPageTable;
> +BOOLEAN                             mCpuSmmRestrictedMemoryAccess;
>  BOOLEAN                             m5LevelPagingSupport;
>  X86_ASSEMBLY_PATCH_LABEL            gPatch5LevelPagingSupport;
> 
> @@ -334,15 +334,15 @@ SmmInitPageTable (
>    //
>    InitializeSpinLock (mPFLock);
> 
> -  mCpuSmmStaticPageTable = PcdGetBool (PcdCpuSmmStaticPageTable);
> -  m1GPageTableSupport    = Is1GPageSupport ();
> -  m5LevelPagingSupport   = Is5LevelPagingSupport ();
> -  mPhysicalAddressBits   = CalculateMaximumSupportAddress ();
> +  mCpuSmmRestrictedMemoryAccess = PcdGetBool
> (PcdCpuSmmRestrictedMemoryAccess);
> +  m1GPageTableSupport           = Is1GPageSupport ();
> +  m5LevelPagingSupport          = Is5LevelPagingSupport ();
> +  mPhysicalAddressBits          = CalculateMaximumSupportAddress ();
>    PatchInstructionX86 (gPatch5LevelPagingSupport, m5LevelPagingSupport, 1);
> -  DEBUG ((DEBUG_INFO, "5LevelPaging Support     - %d\n",
> m5LevelPagingSupport));
> -  DEBUG ((DEBUG_INFO, "1GPageTable Support      - %d\n",
> m1GPageTableSupport));
> -  DEBUG ((DEBUG_INFO, "PcdCpuSmmStaticPageTable - %d\n",
> mCpuSmmStaticPageTable));
> -  DEBUG ((DEBUG_INFO, "PhysicalAddressBits      - %d\n",
> mPhysicalAddressBits));
> +  DEBUG ((DEBUG_INFO, "5LevelPaging Support            - %d\n",
> m5LevelPagingSupport));
> +  DEBUG ((DEBUG_INFO, "1GPageTable Support             - %d\n",
> m1GPageTableSupport));
> +  DEBUG ((DEBUG_INFO, "PcdCpuSmmRestrictedMemoryAccess - %d\n",
> mCpuSmmRestrictedMemoryAccess));
> +  DEBUG ((DEBUG_INFO, "PhysicalAddressBits             - %d\n",
> mPhysicalAddressBits));
>    //
>    // Generate PAE page table for the first 4GB memory space
>    //
> @@ -385,7 +385,11 @@ SmmInitPageTable (
>      PTEntry = Pml5Entry;
>    }
> 
> -  if (mCpuSmmStaticPageTable) {
> +  if (mCpuSmmRestrictedMemoryAccess) {
> +    //
> +    // When access to non-SMRAM memory is restricted, create page table
> +    // that covers all memory space.
> +    //
>      SetStaticPageTable ((UINTN)PTEntry);
>    } else {
>      //
> @@ -972,7 +976,7 @@ SmiPFHandler (
> 
>    PFAddress = AsmReadCr2 ();
> 
> -  if (mCpuSmmStaticPageTable && (PFAddress >= LShiftU64 (1,
> (mPhysicalAddressBits - 1)))) {
> +  if (mCpuSmmRestrictedMemoryAccess && (PFAddress >= LShiftU64 (1,
> + (mPhysicalAddressBits - 1)))) {
>      DumpCpuContext (InterruptType, SystemContext);
>      DEBUG ((DEBUG_ERROR, "Do not support address 0x%lx by processor!\n",
> PFAddress));
>      CpuDeadLoop ();
> @@ -1049,7 +1053,7 @@ SmiPFHandler (
>        goto Exit;
>      }
> 
> -    if (mCpuSmmStaticPageTable && IsSmmCommBufferForbiddenAddress
> (PFAddress)) {
> +    if (mCpuSmmRestrictedMemoryAccess &&
> + IsSmmCommBufferForbiddenAddress (PFAddress)) {
>        DumpCpuContext (InterruptType, SystemContext);
>        DEBUG ((DEBUG_ERROR, "Access SMM communication forbidden address
> (0x%lx)!\n", PFAddress));
>        DEBUG_CODE (
> @@ -1100,26 +1104,26 @@ SetPageTableAttributes (
>    Enable5LevelPaging = (BOOLEAN) (Cr4.Bits.LA57 == 1);
> 
>    //
> -  // Don't do this if
> -  //  - no static page table; or
> +  // Don't mark page table memory as read-only if  //  - no restriction
> + on access to non-SMRAM memory; or
>    //  - SMM heap guard feature enabled; or
>    //      BIT2: SMM page guard enabled
>    //      BIT3: SMM pool guard enabled
>    //  - SMM profile feature enabled
>    //
> -  if (!mCpuSmmStaticPageTable ||
> +  if (!mCpuSmmRestrictedMemoryAccess ||
>        ((PcdGet8 (PcdHeapGuardPropertyMask) & (BIT3 | BIT2)) != 0) ||
>        FeaturePcdGet (PcdCpuSmmProfileEnable)) {
>      //
> -    // Static paging and heap guard could not be enabled at the same time.
> +    // Restriction on access to non-SMRAM memory and heap guard could not
> be enabled at the same time.
>      //
> -    ASSERT (!(mCpuSmmStaticPageTable &&
> +    ASSERT (!(mCpuSmmRestrictedMemoryAccess &&
>                (PcdGet8 (PcdHeapGuardPropertyMask) & (BIT3 | BIT2)) != 0));
> 
>      //
> -    // Static paging and SMM profile could not be enabled at the same time.
> +    // Restriction on access to non-SMRAM memory and SMM profile could not
> be enabled at the same time.
>      //
> -    ASSERT (!(mCpuSmmStaticPageTable && FeaturePcdGet
> (PcdCpuSmmProfileEnable)));
> +    ASSERT (!(mCpuSmmRestrictedMemoryAccess && FeaturePcdGet
> + (PcdCpuSmmProfileEnable)));
>      return ;
>    }
> 
> @@ -1223,7 +1227,10 @@ SaveCr2 (
>    OUT UINTN  *Cr2
>    )
>  {
> -  if (!mCpuSmmStaticPageTable) {
> +  if (!mCpuSmmRestrictedMemoryAccess) {
> +    //
> +    // On-demand paging is enabled when access to non-SMRAM is not
> restricted.
> +    //
>      *Cr2 = AsmReadCr2 ();
>    }
>  }
> @@ -1238,7 +1245,10 @@ RestoreCr2 (
>    IN UINTN  Cr2
>    )
>  {
> -  if (!mCpuSmmStaticPageTable) {
> +  if (!mCpuSmmRestrictedMemoryAccess) {
> +    //
> +    // On-demand paging is enabled when access to non-SMRAM is not
> restricted.
> +    //
>      AsmWriteCr2 (Cr2);
>    }
>  }
> --
> 2.21.0.windows.1


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Re: [edk2-devel] [PATCH 2/5] UefiCpuPkg/PiSmmCpu: Use new PCD PcdCpuSmmRestrictedMemoryAccess
Posted by Laszlo Ersek 6 years, 5 months ago 
On 08/26/19 00:45, Ni, Ray wrote:
> The patch changes PiSmmCpu driver to consume PCD
> PcdCpuSmmRestrictedMemoryAccess.
> Because the behavior controlled by PcdCpuSmmStaticPageTable in
> original code is not changed after switching to
> PcdCpuSmmRestrictedMemoryAccess.
> 
> The functionality is not impacted by this patch.
> 
> Signed-off-by: Ray Ni <ray.ni@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf |  4 +-
>  UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c      | 52 ++++++++++++--------
>  2 files changed, 34 insertions(+), 22 deletions(-)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
> index da0308c47f..b12b2691f8 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
> @@ -133,7 +133,6 @@ [Pcd]
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuHotPlugDataAddress               ## SOMETIMES_PRODUCES
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmCodeAccessCheckEnable         ## CONSUMES
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmSyncMode                      ## CONSUMES
> -  gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStaticPageTable               ## CONSUMES
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmShadowStackSize               ## SOMETIMES_CONSUMES
>    gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiS3Enable                   ## CONSUMES
>    gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask    ## CONSUMES
> @@ -141,6 +140,9 @@ [Pcd]
>    gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPropertyMask               ## CONSUMES
>    gEfiMdePkgTokenSpaceGuid.PcdControlFlowEnforcementPropertyMask        ## CONSUMES
>  
> +[Pcd.X64]
> +  gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmRestrictedMemoryAccess        ## CONSUMES
> +
>  [Depex]
>    gEfiMpServiceProtocolGuid
>  
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> index d60c404a3d..7516f35055 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
> @@ -15,7 +15,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
>  
>  LIST_ENTRY                          mPagePool = INITIALIZE_LIST_HEAD_VARIABLE (mPagePool);
>  BOOLEAN                             m1GPageTableSupport = FALSE;
> -BOOLEAN                             mCpuSmmStaticPageTable;
> +BOOLEAN                             mCpuSmmRestrictedMemoryAccess;
>  BOOLEAN                             m5LevelPagingSupport;
>  X86_ASSEMBLY_PATCH_LABEL            gPatch5LevelPagingSupport;
>  
> @@ -334,15 +334,15 @@ SmmInitPageTable (
>    //
>    InitializeSpinLock (mPFLock);
>  
> -  mCpuSmmStaticPageTable = PcdGetBool (PcdCpuSmmStaticPageTable);
> -  m1GPageTableSupport    = Is1GPageSupport ();
> -  m5LevelPagingSupport   = Is5LevelPagingSupport ();
> -  mPhysicalAddressBits   = CalculateMaximumSupportAddress ();
> +  mCpuSmmRestrictedMemoryAccess = PcdGetBool (PcdCpuSmmRestrictedMemoryAccess);
> +  m1GPageTableSupport           = Is1GPageSupport ();
> +  m5LevelPagingSupport          = Is5LevelPagingSupport ();
> +  mPhysicalAddressBits          = CalculateMaximumSupportAddress ();
>    PatchInstructionX86 (gPatch5LevelPagingSupport, m5LevelPagingSupport, 1);
> -  DEBUG ((DEBUG_INFO, "5LevelPaging Support     - %d\n", m5LevelPagingSupport));
> -  DEBUG ((DEBUG_INFO, "1GPageTable Support      - %d\n", m1GPageTableSupport));
> -  DEBUG ((DEBUG_INFO, "PcdCpuSmmStaticPageTable - %d\n", mCpuSmmStaticPageTable));
> -  DEBUG ((DEBUG_INFO, "PhysicalAddressBits      - %d\n", mPhysicalAddressBits));
> +  DEBUG ((DEBUG_INFO, "5LevelPaging Support            - %d\n", m5LevelPagingSupport));
> +  DEBUG ((DEBUG_INFO, "1GPageTable Support             - %d\n", m1GPageTableSupport));
> +  DEBUG ((DEBUG_INFO, "PcdCpuSmmRestrictedMemoryAccess - %d\n", mCpuSmmRestrictedMemoryAccess));
> +  DEBUG ((DEBUG_INFO, "PhysicalAddressBits             - %d\n", mPhysicalAddressBits));
>    //
>    // Generate PAE page table for the first 4GB memory space
>    //
> @@ -385,7 +385,11 @@ SmmInitPageTable (
>      PTEntry = Pml5Entry;
>    }
>  
> -  if (mCpuSmmStaticPageTable) {
> +  if (mCpuSmmRestrictedMemoryAccess) {
> +    //
> +    // When access to non-SMRAM memory is restricted, create page table
> +    // that covers all memory space.
> +    //
>      SetStaticPageTable ((UINTN)PTEntry);
>    } else {
>      //
> @@ -972,7 +976,7 @@ SmiPFHandler (
>  
>    PFAddress = AsmReadCr2 ();
>  
> -  if (mCpuSmmStaticPageTable && (PFAddress >= LShiftU64 (1, (mPhysicalAddressBits - 1)))) {
> +  if (mCpuSmmRestrictedMemoryAccess && (PFAddress >= LShiftU64 (1, (mPhysicalAddressBits - 1)))) {
>      DumpCpuContext (InterruptType, SystemContext);
>      DEBUG ((DEBUG_ERROR, "Do not support address 0x%lx by processor!\n", PFAddress));
>      CpuDeadLoop ();
> @@ -1049,7 +1053,7 @@ SmiPFHandler (
>        goto Exit;
>      }
>  
> -    if (mCpuSmmStaticPageTable && IsSmmCommBufferForbiddenAddress (PFAddress)) {
> +    if (mCpuSmmRestrictedMemoryAccess && IsSmmCommBufferForbiddenAddress (PFAddress)) {
>        DumpCpuContext (InterruptType, SystemContext);
>        DEBUG ((DEBUG_ERROR, "Access SMM communication forbidden address (0x%lx)!\n", PFAddress));
>        DEBUG_CODE (
> @@ -1100,26 +1104,26 @@ SetPageTableAttributes (
>    Enable5LevelPaging = (BOOLEAN) (Cr4.Bits.LA57 == 1);
>  
>    //
> -  // Don't do this if
> -  //  - no static page table; or
> +  // Don't mark page table memory as read-only if
> +  //  - no restriction on access to non-SMRAM memory; or
>    //  - SMM heap guard feature enabled; or
>    //      BIT2: SMM page guard enabled
>    //      BIT3: SMM pool guard enabled
>    //  - SMM profile feature enabled
>    //
> -  if (!mCpuSmmStaticPageTable ||
> +  if (!mCpuSmmRestrictedMemoryAccess ||
>        ((PcdGet8 (PcdHeapGuardPropertyMask) & (BIT3 | BIT2)) != 0) ||
>        FeaturePcdGet (PcdCpuSmmProfileEnable)) {
>      //
> -    // Static paging and heap guard could not be enabled at the same time.
> +    // Restriction on access to non-SMRAM memory and heap guard could not be enabled at the same time.
>      //
> -    ASSERT (!(mCpuSmmStaticPageTable &&
> +    ASSERT (!(mCpuSmmRestrictedMemoryAccess &&
>                (PcdGet8 (PcdHeapGuardPropertyMask) & (BIT3 | BIT2)) != 0));
>  
>      //
> -    // Static paging and SMM profile could not be enabled at the same time.
> +    // Restriction on access to non-SMRAM memory and SMM profile could not be enabled at the same time.
>      //
> -    ASSERT (!(mCpuSmmStaticPageTable && FeaturePcdGet (PcdCpuSmmProfileEnable)));
> +    ASSERT (!(mCpuSmmRestrictedMemoryAccess && FeaturePcdGet (PcdCpuSmmProfileEnable)));
>      return ;
>    }
>  
> @@ -1223,7 +1227,10 @@ SaveCr2 (
>    OUT UINTN  *Cr2
>    )
>  {
> -  if (!mCpuSmmStaticPageTable) {
> +  if (!mCpuSmmRestrictedMemoryAccess) {
> +    //
> +    // On-demand paging is enabled when access to non-SMRAM is not restricted.
> +    //
>      *Cr2 = AsmReadCr2 ();
>    }
>  }
> @@ -1238,7 +1245,10 @@ RestoreCr2 (
>    IN UINTN  Cr2
>    )
>  {
> -  if (!mCpuSmmStaticPageTable) {
> +  if (!mCpuSmmRestrictedMemoryAccess) {
> +    //
> +    // On-demand paging is enabled when access to non-SMRAM is not restricted.
> +    //
>      AsmWriteCr2 (Cr2);
>    }
>  }
> 

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

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