From 1217f59d23b7c1cc6fa3be658f9ec00bfe0854c0 Mon Sep 17 00:00:00 2001
From: Ray Ni <ray.ni@intel.com>
Date: Thu, 29 Sep 2022 12:48:19 +0800
Subject: UefiCpuPkg/MtrrLib: Fix MtrrSetAllMtrrs to handle absent fixed MTRRs.

Update MtrrSetAllMtrrs to not access fixed MTRRs if CPU doesn't
support them.

Signed-off-by: Ray Ni <ray.ni@intel.com>
Signed-off-by: Yuanhao Xie <yuanhao.xie@intel.com>

Cc: Eric Dong <eric.dong@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>

Reviewed-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
---
 UefiCpuPkg/Include/Library/MtrrLib.h |  9 ++++++---
 UefiCpuPkg/Library/MtrrLib/MtrrLib.c | 26 ++++++++++++++++++++------
 2 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/UefiCpuPkg/Include/Library/MtrrLib.h b/UefiCpuPkg/Include/Library/MtrrLib.h
index 683d9f2c14..94cf615901 100644
--- a/UefiCpuPkg/Include/Library/MtrrLib.h
+++ b/UefiCpuPkg/Include/Library/MtrrLib.h
@@ -1,7 +1,7 @@
 /** @file
   MTRR setting library
 
-  Copyright (c) 2008 - 2020, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2008 - 2023, Intel Corporation. All rights reserved.<BR>
   SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
@@ -214,9 +214,12 @@ MtrrGetAllMtrrs (
 /**
   This function sets all MTRRs (variable and fixed)
 
-  @param[in]  MtrrSetting   A buffer to hold all MTRRs content.
+  Note: The behavior of this function is to program everything in MtrrSetting to hardware.
+        MTRR might not be enabled due to enable bit is clear in MtrrSetting->MtrrDefType.
 
-  @return The pointer of MtrrSetting
+  @param[in]  MtrrSetting  A buffer holding all MTRRs content.
+
+  @retval The pointer of MtrrSetting
 
 **/
 MTRR_SETTINGS *
diff --git a/UefiCpuPkg/Library/MtrrLib/MtrrLib.c b/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
index 255a8ebf81..e9bb153304 100644
--- a/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
+++ b/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
@@ -2869,7 +2869,10 @@ MtrrGetAllMtrrs (
 }
 
 /**
-  This function sets all MTRRs (variable and fixed)
+  This function sets all MTRRs includes Variable and Fixed.
+
+  The behavior of this function is to program everything in MtrrSetting to hardware.
+  MTRRs might not be enabled because the enable bit is clear in MtrrSetting->MtrrDefType.
 
   @param[in]  MtrrSetting  A buffer holding all MTRRs content.
 
@@ -2882,21 +2885,32 @@ MtrrSetAllMtrrs (
   IN MTRR_SETTINGS  *MtrrSetting
   )
 {
-  MTRR_CONTEXT  MtrrContext;
+  BOOLEAN                          FixedMtrrSupported;
+  MSR_IA32_MTRR_DEF_TYPE_REGISTER  *MtrrDefType;
+  MTRR_CONTEXT                     MtrrContext;
 
-  if (!IsMtrrSupported ()) {
+  MtrrDefType = (MSR_IA32_MTRR_DEF_TYPE_REGISTER *)&MtrrSetting->MtrrDefType;
+  if (!MtrrLibIsMtrrSupported (&FixedMtrrSupported, NULL)) {
     return MtrrSetting;
   }
 
   MtrrLibPreMtrrChange (&MtrrContext);
 
   //
-  // Set fixed MTRRs
+  // Enabling the Fixed MTRR bit when unsupported is not allowed.
+  //
+  ASSERT (FixedMtrrSupported || (MtrrDefType->Bits.FE == 0));
+
+  //
+  // If the hardware supports Fixed MTRR, it is sufficient
+  // to set MTRRs regardless of whether Fixed MTRR bit is enabled.
   //
-  MtrrSetFixedMtrrWorker (&MtrrSetting->Fixed);
+  if (FixedMtrrSupported) {
+    MtrrSetFixedMtrrWorker (&MtrrSetting->Fixed);
+  }
 
   //
-  // Set variable MTRRs
+  // Set Variable MTRRs
   //
   MtrrSetVariableMtrrWorker (&MtrrSetting->Variables);
 
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