REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2040
Supports new logic which test current value before write new value.
Only write new value when current value not same as new value.
Signed-off-by: Eric Dong <eric.d...@intel.com>
Cc: Ray Ni <ray...@intel.com>
Acked-by: Laszlo Ersek <ler...@redhat.com>
---
.../CpuFeaturesInitialize.c | 31 ++++++++++++++++++-
1 file changed, 30 insertions(+), 1 deletion(-)
diff --git a/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c
b/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c
index 63bc50a55f..0a4fcff033 100644
--- a/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c
+++ b/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c
@@ -826,6 +826,7 @@ ProgramProcessorRegister (
UINTN ValidThreadCount;
UINT32 *ValidCoreCountPerPackage;
EFI_STATUS Status;
+ UINT64 CurrentValue;
//
// Traverse Register Table of this logical processor
@@ -848,7 +849,16 @@ ProgramProcessorRegister (
if (EFI_ERROR (Status)) {
break;
}
-
+ if (RegisterTableEntry->TestThenWrite) {
+ CurrentValue = BitFieldRead64 (
+ Value,
+ RegisterTableEntry->ValidBitStart,
+ RegisterTableEntry->ValidBitStart +
RegisterTableEntry->ValidBitLength - 1
+ );
+ if (CurrentValue == RegisterTableEntry->Value) {
+ break;
+ }
+ }
Value = (UINTN) BitFieldWrite64 (
Value,
RegisterTableEntry->ValidBitStart,
@@ -857,10 +867,29 @@ ProgramProcessorRegister (
);
ReadWriteCr (RegisterTableEntry->Index, FALSE, &Value);
break;
+
//
// The specified register is Model Specific Register
//
case Msr:
+ if (RegisterTableEntry->TestThenWrite) {
+ Value = (UINTN)AsmReadMsr64 (RegisterTableEntry->Index);
+ if (RegisterTableEntry->ValidBitLength >= 64) {
+ if (Value == RegisterTableEntry->Value) {
+ break;
+ }
+ } else {
+ CurrentValue = BitFieldRead64 (
+ Value,
+ RegisterTableEntry->ValidBitStart,
+ RegisterTableEntry->ValidBitStart +
RegisterTableEntry->ValidBitLength - 1
+ );
+ if (CurrentValue == RegisterTableEntry->Value) {
+ break;
+ }
+ }
+ }
+
if (RegisterTableEntry->ValidBitLength >= 64) {
//
// If length is not less than 64 bits, then directly write without
reading
--
2.21.0.windows.1
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