[PATCH 3/5] UefiCpuPkg/PiSmmCpu: Restrict access per PcdCpuSmmRestrictedMemoryAccess

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

Today's behavior is to always restrict access to non-SMRAM regardless
the value of PcdCpuSmmRestrictedMemoryAccess.

Because RAS components require to access all non-SMRAM memory, the
patch changes the code logic to honor PcdCpuSmmRestrictedMemoryAccess
so that only when the PCD is true, the restriction takes affect and
page table memory is also protected.

Because IA32 build doesn't reference this PCD, such restriction
always takes affect in IA32 build.

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/Ia32/PageTbl.c   | 14 ++++++++++++++
 UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c | 18 ++++++++++--------
 UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h | 11 +++++++++++
 UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c    | 14 ++++++++++++++
 4 files changed, 49 insertions(+), 8 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c
index 05fb455936..f891a81112 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/PageTbl.c
@@ -336,3 +336,17 @@ RestoreCr2 (
 {
   return ;
 }
+
+/**
+  Return whether access to non-SMRAM is restricted.
+
+  @retval TRUE  Access to non-SMRAM is restricted.
+  @retval FALSE Access to non-SMRAM is not restricted.
+*/
+BOOLEAN
+IsRestrictedMemoryAccess (
+  VOID
+  )
+{
+  return TRUE;
+}
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
index 69a04dfb23..723fd5042f 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
@@ -1431,15 +1431,17 @@ PerformRemainingTasks (
     //
     SetMemMapAttributes ();
 
-    //
-    // For outside SMRAM, we only map SMM communication buffer or MMIO.
-    //
-    SetUefiMemMapAttributes ();
+    if (IsRestrictedMemoryAccess ()) {
+      //
+      // For outside SMRAM, we only map SMM communication buffer or MMIO.
+      //
+      SetUefiMemMapAttributes ();
 
-    //
-    // Set page table itself to be read-only
-    //
-    SetPageTableAttributes ();
+      //
+      // Set page table itself to be read-only
+      //
+      SetPageTableAttributes ();
+    }
 
     //
     // Configure SMM Code Access Check feature if available.
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
index 8c29f1a558..daf977f654 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
@@ -1450,4 +1450,15 @@ InitializeDataForMmMp (
   VOID
   );
 
+/**
+  Return whether access to non-SMRAM is restricted.
+
+  @retval TRUE  Access to non-SMRAM is restricted.
+  @retval FALSE Access to non-SMRAM is not restricted.
+*/
+BOOLEAN
+IsRestrictedMemoryAccess (
+  VOID
+  );
+
 #endif
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
index 7516f35055..733d107efd 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
@@ -1252,3 +1252,17 @@ RestoreCr2 (
     AsmWriteCr2 (Cr2);
   }
 }
+
+/**
+  Return whether access to non-SMRAM is restricted.
+
+  @retval TRUE  Access to non-SMRAM is restricted.
+  @retval FALSE Access to non-SMRAM is not restricted.
+*/
+BOOLEAN
+IsRestrictedMemoryAccess (
+  VOID
+  )
+{
+  return mCpuSmmRestrictedMemoryAccess;
+}
-- 
2.21.0.windows.1