UefiCpuPkg: Move AsmRelocateApLoopStart from Mpfuncs.nasm to AmdSev.nasm

[mirror_edk2.git] / OvmfPkg / Library / PlatformDebugLibIoPort / DebugLibDetect.c

diff --git a/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.c b/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.c
index 81c44eece95f04baa1978ae894b3f30a2f90b05c..45207faf5cb2fd8af5547aa94b793df18cbe9651 100644 (file)
--- a/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.c
+++ b/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.c
@@ -1,29 +1,35 @@
 /** @file\r
-  Detection code for QEMU debug port.\r
+  Detection code for hypervisor debug port.\r
   Non-SEC instance, caches the result of detection.\r
 \r
   Copyright (c) 2017, Red Hat, Inc.<BR>\r
-  This program and the accompanying materials\r
-  are licensed and made available under the terms and conditions of the BSD License\r
-  which accompanies this distribution.  The full text of the license may be found at\r
-  http://opensource.org/licenses/bsd-license.php.\r
-\r
-  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
-  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
+  SPDX-License-Identifier: BSD-2-Clause-Patent\r
 \r
 **/\r
 \r
 #include <Base.h>\r
 #include "DebugLibDetect.h"\r
 \r
+//\r
+// Set to TRUE if the debug I/O port has been checked\r
+//\r
+STATIC BOOLEAN  mDebugIoPortChecked = FALSE;\r
+\r
 //\r
 // Set to TRUE if the debug I/O port is enabled\r
 //\r
-STATIC BOOLEAN mDebugIoPortFound = FALSE;\r
+STATIC BOOLEAN  mDebugIoPortFound = FALSE;\r
 \r
 /**\r
-  This constructor function checks if the debug I/O port device is present,\r
-  caching the result for later use.\r
+  This constructor function must not do anything.\r
+\r
+  Some modules consuming this library instance, such as the DXE Core, invoke\r
+  the DEBUG() macro before they explicitly call\r
+  ProcessLibraryConstructorList(). Therefore the auto-generated call from\r
+  ProcessLibraryConstructorList() to this constructor function may be preceded\r
+  by some calls to PlatformDebugLibIoPortFound() below. Hence\r
+  PlatformDebugLibIoPortFound() must not rely on anything this constructor\r
+  could set up.\r
 \r
   @retval RETURN_SUCCESS   The constructor always returns RETURN_SUCCESS.\r
 \r
@@ -34,12 +40,12 @@ PlatformDebugLibIoPortConstructor (
   VOID\r
   )\r
 {\r
-  mDebugIoPortFound = PlatformDebugLibIoPortDetect();\r
   return RETURN_SUCCESS;\r
 }\r
 \r
 /**\r
-  Return the cached result of detecting the debug I/O port device.\r
+  At the first call, check if the debug I/O port device is present, and cache\r
+  the result for later use. At subsequent calls, return the cached result.\r
 \r
   @retval TRUE   if the debug I/O port device was detected.\r
   @retval FALSE  otherwise\r
@@ -51,5 +57,10 @@ PlatformDebugLibIoPortFound (
   VOID\r
   )\r
 {\r
+  if (!mDebugIoPortChecked) {\r
+    mDebugIoPortFound   = PlatformDebugLibIoPortDetect ();\r
+    mDebugIoPortChecked = TRUE;\r
+  }\r
+\r
   return mDebugIoPortFound;\r
 }\r