[PATCH] UefiCpuPkg/SmmCpu: Block SMM read-out only when static paging is used

[Ruiyu Ni <ruiyu.ni@intel.com>]

From: Jiewen Yao <jiewen.yao@intel.com>

Today's implementation blocks SMM read-out no matter static paging
is enabled or not. But certain platform may need to read non-SMM
content from SMM code. These platforms don't have a way to disable
the read-out blocking.

The patch updates the policy to only block SMM read-out when static
paging is enabled. So that the static paging can be disabled for
those platforms that want SMM read-out.

Setting PcdCpuSmmStaticPageTable to FALSE can disable the static
paging.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Ruiyu Ni <ruiyu.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/X64/PageTbl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
index 5bb7d57238..117502dafa 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/PageTbl.c
@@ -1,7 +1,7 @@
 /** @file
 Page Fault (#PF) handler for X64 processors
 
-Copyright (c) 2009 - 2017, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2009 - 2018, Intel Corporation. All rights reserved.<BR>
 Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
 
 This program and the accompanying materials
@@ -890,7 +890,7 @@ SmiPFHandler (
       CpuDeadLoop ();
     }
 
-    if (IsSmmCommBufferForbiddenAddress (PFAddress)) {
+    if (mCpuSmmStaticPageTable && IsSmmCommBufferForbiddenAddress (PFAddress)) {
       DumpCpuContext (InterruptType, SystemContext);
       DEBUG ((DEBUG_ERROR, "Access SMM communication forbidden address (0x%lx)!\n", PFAddress));
       DEBUG_CODE (
-- 
2.16.1.windows.1