[edk2] [PATCH] IntelFsp2Pkg: FSP should not override IDT

[Chasel, Chiu]

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1265

FSP should not override IDT table when it is initialized
by boot loader. IDT should be re-initialized in FSP only
when it is invalid.

Test: Verified on internal platform and boots successfully.

Cc: Jiewen Yao <jiewen....@intel.com>
Cc: Desimone Nathaniel L <nathaniel.l.desim...@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Chasel Chiu <chasel.c...@intel.com>
---
 IntelFsp2Pkg/FspSecCore/SecMain.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/IntelFsp2Pkg/FspSecCore/SecMain.c 
b/IntelFsp2Pkg/FspSecCore/SecMain.c
index 37fd4dfdeb..5912221204 100644
--- a/IntelFsp2Pkg/FspSecCore/SecMain.c
+++ b/IntelFsp2Pkg/FspSecCore/SecMain.c
@@ -70,6 +70,7 @@ SecStartup (
   UINT32                      Index;
   FSP_GLOBAL_DATA             PeiFspData;
   UINT64                      ExceptionHandler;
+  UINTN                       IdtSize;
 
   //
   // Process all libraries constructor function linked to SecCore.
@@ -98,13 +99,24 @@ SecStartup (
   // |                   |
   // |-------------------|---->  TempRamBase
   IdtTableInStack.PeiService  = NULL;
-  ExceptionHandler = FspGetExceptionHandler(mIdtEntryTemplate);
-  for (Index = 0; Index < SEC_IDT_ENTRY_COUNT; Index ++) {
-    CopyMem ((VOID*)&IdtTableInStack.IdtTable[Index], 
(VOID*)&ExceptionHandler, sizeof (UINT64));
+  AsmReadIdtr (&IdtDescriptor);
+  if ((IdtDescriptor.Base == 0) && (IdtDescriptor.Limit == 0xFFFF)) {
+    ExceptionHandler = FspGetExceptionHandler(mIdtEntryTemplate);
+    for (Index = 0; Index < SEC_IDT_ENTRY_COUNT; Index ++) {
+      CopyMem ((VOID*)&IdtTableInStack.IdtTable[Index], 
(VOID*)&ExceptionHandler, sizeof (UINT64));
+    }
+    IdtSize = sizeof (IdtTableInStack.IdtTable);
+  } else {
+    // Get minimum size
+    if (IdtDescriptor.Limit + 1 > sizeof (IdtTableInStack.IdtTable)) {
+      IdtSize = sizeof (IdtTableInStack.IdtTable);
+    } else {
+      IdtSize = IdtDescriptor.Limit + 1;
+    }
+    CopyMem ((VOID *) (UINTN) &IdtTableInStack.IdtTable, (VOID *) 
IdtDescriptor.Base, IdtSize);
   }
-
   IdtDescriptor.Base  = (UINTN) &IdtTableInStack.IdtTable;
-  IdtDescriptor.Limit = (UINT16)(sizeof (IdtTableInStack.IdtTable) - 1);
+  IdtDescriptor.Limit = (UINT16)(IdtSize - 1);
 
   AsmWriteIdtr (&IdtDescriptor);
 
-- 
2.13.3.windows.1

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