[PATCH v2] UefiCpuPkg/DxeMpLib: Allocate below 4GB mem for AsmRelocateApLoopFunc

[Jeff Fan <jeff.fan@intel.com>]

Current implementation just allocates reserve memory for AsmRelocateApLoopFunc.
It not be safe because APs will be placed into 32bit protected mode on long mode
DXE. This reserve memory must be located below 4GB memory.

This fix is to allocate < 4GB memory for AsmRelocateApLoopFunc.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
---
 UefiCpuPkg/Library/MpInitLib/DxeMpLib.c | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
index eb36d6f..4b929ff 100644
--- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
@@ -286,7 +286,8 @@ InitMpGlobalData (
   IN CPU_MP_DATA               *CpuMpData
   )
 {
-  EFI_STATUS     Status;
+  EFI_STATUS                 Status;
+  EFI_PHYSICAL_ADDRESS       Address;
 
   SaveCpuMpData (CpuMpData);
 
@@ -298,16 +299,28 @@ InitMpGlobalData (
   }
 
   //
-  // Avoid APs access invalid buff data which allocated by BootServices,
-  // so we will allocate reserved data for AP loop code.
+  // Avoid APs access invalid buffer data which allocated by BootServices,
+  // so we will allocate reserved data for AP loop code. We also need to 
+  // allocate this buffer below 4GB due to APs may be transferred to 32bit
+  // protected mode on long mode DXE.
   // Allocating it in advance since memory services are not available in
   // Exit Boot Services callback function.
   //
-  mReservedApLoopFunc = AllocateReservedCopyPool (
-                          CpuMpData->AddressMap.RelocateApLoopFuncSize,
-                          CpuMpData->AddressMap.RelocateApLoopFuncAddress
-                          );
+  Address = BASE_4GB - 1;
+  Status  = gBS->AllocatePages (
+                   AllocateMaxAddress,
+                   EfiReservedMemoryType,
+                   EFI_SIZE_TO_PAGES (sizeof (CpuMpData->AddressMap.RelocateApLoopFuncSize)),
+                   &Address
+                   );
+  ASSERT_EFI_ERROR (Status);
+  mReservedApLoopFunc = (VOID *) (UINTN) Address;
   ASSERT (mReservedApLoopFunc != NULL);
+  CopyMem (
+    mReservedApLoopFunc,
+    CpuMpData->AddressMap.RelocateApLoopFuncAddress,
+    CpuMpData->AddressMap.RelocateApLoopFuncSize
+    );
 
   Status = gBS->CreateEvent (
                   EVT_TIMER | EVT_NOTIFY_SIGNAL,
-- 
2.9.3.windows.2