Current X2APIC is enabled in MpInitLib (used by CpuMpPei and CpuDxe) to follow
SDM suggestion. That means we only enable X2APIC if we found there are any
initial CPU ID value >= 255.

This patch is to provide one chance for platform to enable X2APIC even there is
no any initial CPU ID value >= 255.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
---
 .../CpuCommonFeaturesLib/CpuCommonFeatures.h       | 15 +++++
 .../CpuCommonFeaturesLib/CpuCommonFeaturesLib.c    |  2 +-
 UefiCpuPkg/Library/CpuCommonFeaturesLib/X2Apic.c   | 77 +++++++++++++++++++---
 3 files changed, 83 insertions(+), 11 deletions(-)

diff --git a/UefiCpuPkg/Library/CpuCommonFeaturesLib/CpuCommonFeatures.h b/UefiCpuPkg/Library/CpuCommonFeaturesLib/CpuCommonFeatures.h
index aa6d112..9a7afed 100644
--- a/UefiCpuPkg/Library/CpuCommonFeaturesLib/CpuCommonFeatures.h
+++ b/UefiCpuPkg/Library/CpuCommonFeaturesLib/CpuCommonFeatures.h
@@ -798,6 +798,21 @@ C1eInitialize (
   );
 
 /**
+  Prepares for the data used by CPU feature detection and initialization.
+
+  @param[in]  NumberOfProcessors  The number of CPUs in the platform.
+
+  @return  Pointer to a buffer of CPU related configuration data.
+
+  @note This service could be called by BSP only.
+**/
+VOID *
+EFIAPI
+X2ApicGetConfigData (
+  IN UINTN  NumberOfProcessors
+  );
+
+/**
   Detects if X2Apci feature supported on current processor.
 
   Detect if X2Apci has been already enabled.
diff --git a/UefiCpuPkg/Library/CpuCommonFeaturesLib/CpuCommonFeaturesLib.c b/UefiCpuPkg/Library/CpuCommonFeaturesLib/CpuCommonFeaturesLib.c
index 3390aa8..793a095 100644
--- a/UefiCpuPkg/Library/CpuCommonFeaturesLib/CpuCommonFeaturesLib.c
+++ b/UefiCpuPkg/Library/CpuCommonFeaturesLib/CpuCommonFeaturesLib.c
@@ -211,7 +211,7 @@ CpuCommonFeaturesLibConstructor (
   if (IsCpuFeatureSupported (CPU_FEATURE_X2APIC)) {
     Status = RegisterCpuFeature (
                "X2Apic",
-               NULL,
+               X2ApicGetConfigData,
                X2ApicSupport,
                X2ApicInitialize,
                CPU_FEATURE_X2APIC,
diff --git a/UefiCpuPkg/Library/CpuCommonFeaturesLib/X2Apic.c b/UefiCpuPkg/Library/CpuCommonFeaturesLib/X2Apic.c
index 9c2ad9a..6673c95 100644
--- a/UefiCpuPkg/Library/CpuCommonFeaturesLib/X2Apic.c
+++ b/UefiCpuPkg/Library/CpuCommonFeaturesLib/X2Apic.c
@@ -15,6 +15,28 @@
 #include "CpuCommonFeatures.h"
 
 /**
+  Prepares for the data used by CPU feature detection and initialization.
+
+  @param[in]  NumberOfProcessors  The number of CPUs in the platform.
+
+  @return  Pointer to a buffer of CPU related configuration data.
+
+  @note This service could be called by BSP only.
+**/
+VOID *
+EFIAPI
+X2ApicGetConfigData (
+  IN UINTN  NumberOfProcessors
+  )
+{
+  BOOLEAN                            *ConfigData;
+
+  ConfigData = AllocateZeroPool (sizeof (BOOLEAN) * NumberOfProcessors);
+  ASSERT (ConfigData != NULL);
+  return ConfigData;
+}
+
+/**
   Detects if X2Apci feature supported on current processor.
 
   Detect if X2Apci has been already enabled.
@@ -39,8 +61,17 @@ X2ApicSupport (
   IN REGISTER_CPU_FEATURE_INFORMATION  *CpuInfo,
   IN VOID                              *ConfigData  OPTIONAL
   )
-{
-  return (GetApicMode () == LOCAL_APIC_MODE_X2APIC);
+{  
+  BOOLEAN                            *X2ApicEnabled;
+
+  ASSERT (ConfigData != NULL);
+  X2ApicEnabled = (BOOLEAN *) ConfigData;
+  //
+  // *ConfigData indicates if X2APIC enabled on current processor
+  //
+  X2ApicEnabled[ProcessorNumber] = (GetApicMode () == LOCAL_APIC_MODE_X2APIC) ? TRUE : FALSE;
+
+  return (CpuInfo->CpuIdVersionInfoEcx.Bits.x2APIC == 1);
 }
 
 /**
@@ -69,13 +100,39 @@ X2ApicInitialize (
   IN BOOLEAN                           State
   )
 {
-  PRE_SMM_CPU_REGISTER_TABLE_WRITE_FIELD (
-    ProcessorNumber,
-    Msr,
-    MSR_IA32_APIC_BASE,
-    MSR_IA32_APIC_BASE_REGISTER,
-    Bits.EXTD,
-    (State) ? 1 : 0
-    );
+  BOOLEAN                            *X2ApicEnabled;
+
+  ASSERT (ConfigData != NULL);
+  X2ApicEnabled = (BOOLEAN *) ConfigData;
+  if (X2ApicEnabled[ProcessorNumber]) {
+    if (!State) {
+      DEBUG ((DEBUG_ERROR, "X2APIC should be enabled by PcdCpuFeaturesUserConfiguration!\n"));
+      ASSERT (FALSE);
+    } else {
+      PRE_SMM_CPU_REGISTER_TABLE_WRITE_FIELD (
+        ProcessorNumber,
+        Msr,
+        MSR_IA32_APIC_BASE,
+        MSR_IA32_APIC_BASE_REGISTER,
+        Bits.EXTD,
+        1
+        );
+    }
+  } else {
+    //
+    // Enable X2APIC mode only if X2APIC is not enabled,
+    // Needn't to disabe X2APIC mode again if X2APIC is not enabled
+    //
+    if (State) {
+      CPU_REGISTER_TABLE_WRITE_FIELD (
+        ProcessorNumber,
+        Msr,
+        MSR_IA32_APIC_BASE,
+        MSR_IA32_APIC_BASE_REGISTER,
+        Bits.EXTD,
+        1
+        );
+    }
+  }
   return RETURN_SUCCESS;
 }
-- 
2.9.3.windows.2

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