UefiCpuPkg/MpInitLib: split wake up buffer into two parts

[mirror_edk2.git] / UefiCpuPkg / Library / MpInitLib / DxeMpLib.c

diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
index d2bcef53d695ea828c795a854fdce1b9c15620b8..fd2317924fd1fd998e0523edcaa14baef35ec3e7 100644 (file)
--- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
@@ -113,6 +113,40 @@ GetWakeupBuffer (
   return (UINTN) StartAddress;\r
 }\r
 \r
+/**\r
+  Get available EfiBootServicesCode memory below 4GB by specified size.\r
+\r
+  This buffer is required to safely transfer AP from real address mode to\r
+  protected mode or long mode, due to the fact that the buffer returned by\r
+  GetWakeupBuffer() may be marked as non-executable.\r
+\r
+  @param[in] BufferSize   Wakeup transition buffer size.\r
+\r
+  @retval other   Return wakeup transition buffer address below 4GB.\r
+  @retval 0       Cannot find free memory below 4GB.\r
+**/\r
+UINTN\r
+GetModeTransitionBuffer (\r
+  IN UINTN                BufferSize\r
+  )\r
+{\r
+  EFI_STATUS              Status;\r
+  EFI_PHYSICAL_ADDRESS    StartAddress;\r
+\r
+  StartAddress = BASE_4GB - 1;\r
+  Status = gBS->AllocatePages (\r
+                  AllocateMaxAddress,\r
+                  EfiBootServicesCode,\r
+                  EFI_SIZE_TO_PAGES (BufferSize),\r
+                  &StartAddress\r
+                  );\r
+  if (EFI_ERROR (Status)) {\r
+    StartAddress = 0;\r
+  }\r
+\r
+  return (UINTN)StartAddress;\r
+}\r
+\r
 /**\r
   Checks APs status and updates APs status if needed.\r
 \r