[edk2-devel] [Patch V3 1/3] UefiCpuPkg/MpInitLib: Eliminate redundant microcode loading in DXE.

["Yuanhao Xie" <yuanhao.xie@intel.com>]

The DXE stage's Microcode loading process has been elimincated by:

1. Let ShadowMicrocodeUpdatePatch and MicrocodeDetect for BSP performed
only during the PEI phase. DXE skip those actions.
2. BSP in DXE WakeUpAp only for synchronizing MTRR settings, not loading
microcode.

Synchronizing the MTRR table to the AP is always essential.
During the DXE phase, it cannot be omitted like loading microcode,
as the PEI and DXE may be in different bit modes.

Cc: Ray Ni <ray.ni@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Yuanhao Xie <yuanhao.xie@intel.com>
---
 UefiCpuPkg/Library/MpInitLib/MpLib.c | 38 +++++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
index 9a6ec5db5c..c26a17e1db 100644
--- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
@@ -451,12 +451,19 @@ ApInitializeSync (
   CpuMpData = (CPU_MP_DATA *)Buffer;
   Status    = GetProcessorNumber (CpuMpData, &ProcessorNumber);
   ASSERT_EFI_ERROR (Status);
+  ASSERT (CpuMpData->InitFlag == ApInitReconfig || CpuMpData->InitFlag == ApInitDone);
+  if (CpuMpData->InitFlag != ApInitReconfig) {
+    //
+    // Load microcode on AP for PEI phase.
+    // During the DXE phase, it cannot omitted.
+    //
+    MicrocodeDetect (CpuMpData, ProcessorNumber);
+  }
+
   //
-  // Load microcode on AP
-  //
-  MicrocodeDetect (CpuMpData, ProcessorNumber);
-  //
-  // Sync BSP's MTRR table to AP
+  // Synchronizing the MTRR table to the AP is always essential.
+  // During the DXE phase, it cannot be omitted like loading microcode,
+  // as the PEI and DXE may be in different bit modes.
   //
   MtrrSetAllMtrrs (&CpuMpData->MtrrTable);
 }
@@ -2224,29 +2231,25 @@ MpInitLibInitialize (
     }
   }
 
-  if (!GetMicrocodePatchInfoFromHob (
-         &CpuMpData->MicrocodePatchAddress,
-         &CpuMpData->MicrocodePatchRegionSize
-         ))
-  {
+  if (MpHandOff == NULL) {
     //
     // The microcode patch information cache HOB does not exist, which means
     // the microcode patches data has not been loaded into memory yet
     //
     ShadowMicrocodeUpdatePatch (CpuMpData);
+    //
+    // Detect and apply Microcode on BSP
+    //
+    MicrocodeDetect (CpuMpData, CpuMpData->BspNumber);
   }
 
-  //
-  // Detect and apply Microcode on BSP
-  //
-  MicrocodeDetect (CpuMpData, CpuMpData->BspNumber);
   //
   // Store BSP's MTRR setting
   //
   MtrrGetAllMtrrs (&CpuMpData->MtrrTable);
 
   //
-  // Wakeup APs to do some AP initialize sync (Microcode & MTRR)
+  // Wakeup APs to do some AP initialize sync (MTRR and/or Microcode).
   //
   if (CpuMpData->CpuCount > 1) {
     if (MpHandOff != NULL) {
@@ -2258,6 +2261,11 @@ MpInitLibInitialize (
       CpuMpData->InitFlag = ApInitReconfig;
     }
 
+    //
+    // Wake up the AP to perform some AP initialization synchronization.
+    // 1. For PEI stage, load microcode and synchronize MTRR,
+    // 2. For the DXE phase, only synchronize MTRR.
+    //
     WakeUpAP (CpuMpData, TRUE, 0, ApInitializeSync, CpuMpData, TRUE);
     //
     // Wait for all APs finished initialization
-- 
2.39.1.windows.1



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