[Patch V3 2/8] MdePkg/BaseLib: Use PcdSpeculationBarrierType

["Michael D Kinney" <michael.d.kinney@intel.com>]

Use PcdSpeculationBarrierType in the x86 implementation
of SpeculationBarrier() to select between AsmLfence(),
AsmCpuid(), and no operation.

Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
---
 MdePkg/Library/BaseLib/BaseLib.inf             | 1 +
 MdePkg/Library/BaseLib/X86SpeculationBarrier.c | 8 ++++++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/MdePkg/Library/BaseLib/BaseLib.inf b/MdePkg/Library/BaseLib/BaseLib.inf
index 533e83e0b2..3586beb0ab 100644
--- a/MdePkg/Library/BaseLib/BaseLib.inf
+++ b/MdePkg/Library/BaseLib/BaseLib.inf
@@ -394,6 +394,7 @@ [Pcd]
   gEfiMdePkgTokenSpaceGuid.PcdMaximumAsciiStringLength     ## SOMETIMES_CONSUMES
   gEfiMdePkgTokenSpaceGuid.PcdMaximumUnicodeStringLength   ## SOMETIMES_CONSUMES
   gEfiMdePkgTokenSpaceGuid.PcdControlFlowEnforcementPropertyMask   ## SOMETIMES_CONSUMES
+  gEfiMdePkgTokenSpaceGuid.PcdSpeculationBarrierType       ## SOMETIMES_CONSUMES
 
 [FeaturePcd]
   gEfiMdePkgTokenSpaceGuid.PcdVerifyNodeInList  ## CONSUMES
diff --git a/MdePkg/Library/BaseLib/X86SpeculationBarrier.c b/MdePkg/Library/BaseLib/X86SpeculationBarrier.c
index 8e5f983bb8..b28fd8de9b 100644
--- a/MdePkg/Library/BaseLib/X86SpeculationBarrier.c
+++ b/MdePkg/Library/BaseLib/X86SpeculationBarrier.c
@@ -1,7 +1,7 @@
 /** @file
   SpeculationBarrier() function for IA32 and x64.
 
-  Copyright (C) 2018, Intel Corporation. All rights reserved.<BR>
+  Copyright (C) 2018 - 2019, Intel Corporation. All rights reserved.<BR>
 
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
@@ -22,5 +22,9 @@ SpeculationBarrier (
   VOID
   )
 {
-  AsmLfence ();
+  if (PcdGet8 (PcdSpeculationBarrierType) == 0x01) {
+    AsmLfence ();
+  } else if (PcdGet8 (PcdSpeculationBarrierType) == 0x02) {
+    AsmCpuid (0x01, NULL, NULL, NULL, NULL);
+  }
 }
-- 
2.21.0.windows.1