Current implementation only loads the latest revision if there is no microcode
loaded. Per IA32 User Manual, we should load the newer revision by comparing
the existing microcode loaded with the updating revision.
Cc: Feng Tian <feng.t...@intel.com>
Cc: Michael Kinney <michael.d.kin...@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff....@intel.com>
---
UefiCpuPkg/CpuMpPei/Microcode.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/UefiCpuPkg/CpuMpPei/Microcode.c b/UefiCpuPkg/CpuMpPei/Microcode.c
index 70e149b..9dcbf99 100644
--- a/UefiCpuPkg/CpuMpPei/Microcode.c
+++ b/UefiCpuPkg/CpuMpPei/Microcode.c
@@ -1,7 +1,7 @@
/** @file
Implementation of loading microcode on processors.
- Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>
+ Copyright (c) 2015 - 2016, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD
License
which accompanies this distribution. The full text of the license may be
found at
@@ -57,7 +57,6 @@ MicrocodeDetect (
UINTN TotalSize;
UINT32 CheckSum32;
BOOLEAN CorrectMicrocode;
- INT32 CurrentSignature;
MICROCODE_INFO MicrocodeInfo;
ZeroMem (&MicrocodeInfo, sizeof (MICROCODE_INFO));
@@ -181,17 +180,20 @@ MicrocodeDetect (
if (LatestRevision > 0) {
//
- // Get microcode update signature of currently loaded microcode update
+ // BIOS only authenticate updates that contain a numerically larger
revision
+ // than the currently loaded revision, where Current Signature < New Update
+ // Revision. A processor with no loaded update is considered to have a
+ // revision equal to zero.
//
- CurrentSignature = GetCurrentMicrocodeSignature ();
- //
- // If no microcode update has been loaded, then trigger microcode load.
- //
- if (CurrentSignature == 0) {
+ if (LatestRevision > GetCurrentMicrocodeSignature ()) {
AsmWriteMsr64 (
EFI_MSR_IA32_BIOS_UPDT_TRIG,
(UINT64) (UINTN) MicrocodeInfo.MicrocodeData
);
+ //
+ // Get and verify new microcode signature
+ //
+ ASSERT (LatestRevision == GetCurrentMicrocodeSignature ());
MicrocodeInfo.Load = TRUE;
} else {
MicrocodeInfo.Load = FALSE;
--
1.9.5.msysgit.0
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