From 944f45ae2f7ecbff2c66622d15d52ffbc3455bfb Mon Sep 17 00:00:00 2001
From: Michael Kinney <michael.d.kinney@intel.com>
Date: Mon, 19 Oct 2015 19:07:52 +0000
Subject: [PATCH] UefiCpuPkg: Update CPU MP drivers to support single CPU
 configuration

Only perform AP detection if PcdCpuMaxLogicalProcessorNumber > 1
Only free AP related structures of they were allocated

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18629 6f19259b-4bc3-4df7-8a09-765794883524
---
 UefiCpuPkg/CpuDxe/CpuMp.c      | 49 +++++++++++++++++++---------------
 UefiCpuPkg/CpuMpPei/CpuMpPei.c | 34 +++++++++++++----------
 2 files changed, 48 insertions(+), 35 deletions(-)

diff --git a/UefiCpuPkg/CpuDxe/CpuMp.c b/UefiCpuPkg/CpuDxe/CpuMp.c
index 4ddcca208a..da3686e278 100644
--- a/UefiCpuPkg/CpuDxe/CpuMp.c
+++ b/UefiCpuPkg/CpuDxe/CpuMp.c
@@ -1642,35 +1642,40 @@ InitializeMpSupport (
     return;
   }
 
-  if (gMaxLogicalProcessorNumber == 1) {
-    return;
-  }
 
-  gApStackSize = (UINTN) PcdGet32 (PcdCpuApStackSize);
-  ASSERT ((gApStackSize & (SIZE_4KB - 1)) == 0);
 
-  mApStackStart = AllocatePages (EFI_SIZE_TO_PAGES (gMaxLogicalProcessorNumber * gApStackSize));
-  ASSERT (mApStackStart != NULL);
+  InitMpSystemData ();
 
   //
-  // the first buffer of stack size used for common stack, when the amount of AP
-  // more than 1, we should never free the common stack which maybe used for AP reset.
+  // Only perform AP detection if PcdCpuMaxLogicalProcessorNumber is greater than 1
   //
-  mCommonStack = mApStackStart;
-  mTopOfApCommonStack = (UINT8*) mApStackStart + gApStackSize;
-  mApStackStart = mTopOfApCommonStack;
+  if (gMaxLogicalProcessorNumber > 1) {
 
-  InitMpSystemData ();
+    gApStackSize = (UINTN) PcdGet32 (PcdCpuApStackSize);
+    ASSERT ((gApStackSize & (SIZE_4KB - 1)) == 0);
+
+    mApStackStart = AllocatePages (EFI_SIZE_TO_PAGES (gMaxLogicalProcessorNumber * gApStackSize));
+    ASSERT (mApStackStart != NULL);
+
+    //
+    // the first buffer of stack size used for common stack, when the amount of AP
+    // more than 1, we should never free the common stack which maybe used for AP reset.
+    //
+    mCommonStack = mApStackStart;
+    mTopOfApCommonStack = (UINT8*) mApStackStart + gApStackSize;
+    mApStackStart = mTopOfApCommonStack;
 
-  PrepareAPStartupCode ();
+    PrepareAPStartupCode ();
 
-  StartApsStackless ();
+    StartApsStackless ();
+  }
 
   DEBUG ((DEBUG_INFO, "Detect CPU count: %d\n", mMpSystemData.NumberOfProcessors));
   if (mMpSystemData.NumberOfProcessors == 1) {
     FreeApStartupCode ();
-    FreePages (mCommonStack, EFI_SIZE_TO_PAGES (gMaxLogicalProcessorNumber * gApStackSize));
-    return;
+    if (mCommonStack != NULL) {
+      FreePages (mCommonStack, EFI_SIZE_TO_PAGES (gMaxLogicalProcessorNumber * gApStackSize));
+    }
   }
 
   mMpSystemData.CpuDatas = ReallocatePool (
@@ -1692,10 +1697,12 @@ InitializeMpSupport (
                   );
   ASSERT_EFI_ERROR (Status);
 
-  if (mMpSystemData.NumberOfProcessors < gMaxLogicalProcessorNumber) {
-    FreePages (mApStackStart, EFI_SIZE_TO_PAGES (
-                                (gMaxLogicalProcessorNumber - mMpSystemData.NumberOfProcessors) *
-                                gApStackSize));
+  if (mMpSystemData.NumberOfProcessors > 1 && mMpSystemData.NumberOfProcessors < gMaxLogicalProcessorNumber) {
+    if (mApStackStart != NULL) {
+      FreePages (mApStackStart, EFI_SIZE_TO_PAGES (
+                                  (gMaxLogicalProcessorNumber - mMpSystemData.NumberOfProcessors) *
+                                  gApStackSize));
+    }
   }
 
   Status = gBS->CreateEvent (
diff --git a/UefiCpuPkg/CpuMpPei/CpuMpPei.c b/UefiCpuPkg/CpuMpPei/CpuMpPei.c
index d5bc0c9b80..8e35f288fe 100644
--- a/UefiCpuPkg/CpuMpPei/CpuMpPei.c
+++ b/UefiCpuPkg/CpuMpPei/CpuMpPei.c
@@ -357,22 +357,28 @@ CountProcessorNumber (
   // Store BSP's MTRR setting
   //
   MtrrGetAllMtrrs (&PeiCpuMpData->MtrrTable);
+
   //
-  // Send broadcast IPI to APs to wakeup APs
-  //
-  PeiCpuMpData->InitFlag = 1;
-  WakeUpAP (PeiCpuMpData, TRUE, 0, NULL, NULL);
-  //
-  // Wait for AP task to complete and then exit.
-  //
-  MicroSecondDelay (PcdGet32 (PcdCpuApInitTimeOutInMicroSeconds));
-  PeiCpuMpData->InitFlag  = 0;
-  PeiCpuMpData->CpuCount += (UINT32) PeiCpuMpData->MpCpuExchangeInfo->NumApsExecuting;
-  ASSERT (PeiCpuMpData->CpuCount <= PcdGet32(PcdCpuMaxLogicalProcessorNumber));
-  //
-  // Sort BSP/Aps by CPU APIC ID in ascending order
+  // Only perform AP detection if PcdCpuMaxLogicalProcessorNumber is greater than 1
   //
-  SortApicId (PeiCpuMpData);
+  if (PcdGet32 (PcdCpuMaxLogicalProcessorNumber) > 1) {
+    //
+    // Send broadcast IPI to APs to wakeup APs
+    //
+    PeiCpuMpData->InitFlag = 1;
+    WakeUpAP (PeiCpuMpData, TRUE, 0, NULL, NULL);
+    //
+    // Wait for AP task to complete and then exit.
+    //
+    MicroSecondDelay (PcdGet32 (PcdCpuApInitTimeOutInMicroSeconds));
+    PeiCpuMpData->InitFlag = 0;
+    PeiCpuMpData->CpuCount += (UINT32)PeiCpuMpData->MpCpuExchangeInfo->NumApsExecuting;
+    ASSERT (PeiCpuMpData->CpuCount <= PcdGet32 (PcdCpuMaxLogicalProcessorNumber));
+    //
+    // Sort BSP/Aps by CPU APIC ID in ascending order
+    //
+    SortApicId (PeiCpuMpData);
+  }
 
   DEBUG ((EFI_D_INFO, "CpuMpPei: Find %d processors in system.\n", PeiCpuMpData->CpuCount));
   return PeiCpuMpData->CpuCount;
-- 
2.39.2