REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2434

Current code use below loops to enumerate the CPUs:
  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
it has no issue but not easy for the developers to read the code.

Update above code to below style,
  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
It make the developers easy to read and consistent with other
similar cases in this driver.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Eric Dong <eric.dong@intel.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
index f445d7b030..35a6996ba3 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
@@ -1,7 +1,7 @@
 /** @file
 SMM MP service implementation
 
-Copyright (c) 2009 - 2019, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2009 - 2020, Intel Corporation. All rights reserved.<BR>
 Copyright (c) 2017, AMD Incorporated. All rights reserved.<BR>
 
 SPDX-License-Identifier: BSD-2-Clause-Patent
@@ -137,7 +137,7 @@ ReleaseAllAPs (
 {
   UINTN                             Index;
 
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     if (IsPresentAp (Index)) {
       ReleaseSemaphore (mSmmMpSyncData->CpuData[Index].Run);
     }
@@ -170,7 +170,7 @@ AllCpusInSmmWithExceptions (
 
   CpuData = mSmmMpSyncData->CpuData;
   ProcessorInfo = gSmmCpuPrivate->ProcessorInfo;
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     if (!(*(CpuData[Index].Present)) && ProcessorInfo[Index].ProcessorId != INVALID_APIC_ID) {
       if (((Exceptions & ARRIVAL_EXCEPTION_DELAYED) != 0) && SmmCpuFeaturesGetSmmRegister (Index, SmmRegSmmDelayed) != 0) {
         continue;
@@ -305,7 +305,7 @@ SmmWaitForApArrival (
     //
     // Send SMI IPIs to bring outside processors in
     //
-    for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+    for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
       if (!(*(mSmmMpSyncData->CpuData[Index].Present)) && gSmmCpuPrivate->ProcessorInfo[Index].ProcessorId != INVALID_APIC_ID) {
         SendSmiIpi ((UINT32)gSmmCpuPrivate->ProcessorInfo[Index].ProcessorId);
       }
@@ -361,7 +361,7 @@ WaitForAllAPsNotBusy (
 {
   UINTN                             Index;
 
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     //
     // Ignore BSP and APs which not call in SMM.
     //
@@ -608,7 +608,7 @@ BSPHandler (
     //
     while (TRUE) {
       PresentCount = 0;
-      for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+      for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
         if (*(mSmmMpSyncData->CpuData[Index].Present)) {
           PresentCount ++;
         }
@@ -1343,7 +1343,7 @@ InternalSmmStartupAllAPs (
   }
 
   CpuCount = 0;
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     if (IsPresentAp (Index)) {
       CpuCount ++;
 
@@ -1375,13 +1375,13 @@ InternalSmmStartupAllAPs (
   // Here code always use AcquireSpinLock instead of AcquireSpinLockOrFail for not
   // block mode.
   //
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     if (IsPresentAp (Index)) {
       AcquireSpinLock (mSmmMpSyncData->CpuData[Index].Busy);
     }
   }
 
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     if (IsPresentAp (Index)) {
       mSmmMpSyncData->CpuData[Index].Procedure = (EFI_AP_PROCEDURE2) Procedure;
       mSmmMpSyncData->CpuData[Index].Parameter = ProcedureArguments;
-- 
2.23.0.windows.1


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