UefiCpuPkg/PiSmmCpuDxeSmm: Reduce the times of BSP and AP sync for exit

After review, there are unnecessary steps for BSP and AP sync for exit. This patch is to reduce one round BSP and AP sync for exit so as to improve SMM performance: WaitForAllAPs <- ReleaseBsp ReleaseAllAPs -> WaitForBsp Cc: Eric Dong <[email protected]> Cc: Ray Ni <[email protected]> Cc: Zeng Star <[email protected]> Cc: Rahul Kumar <[email protected]> Cc: Gerd Hoffmann <[email protected]> Signed-off-by: Jiaxin Wu <[email protected]>
tianocore · Oct 11, 2023 · 055092a · 055092a
1 parent 3c47613
commit 055092a
Showing 1 changed file with 24 additions and 20 deletions.
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
@@ -667,7 +667,9 @@ BSPHandler (
     ApCount                        = LockdownSemaphore (mSmmMpSyncData->Counter) - 1;
 
     //
-    // Wait for all APs to get ready for programming MTRRs
+    // Wait for all APs:
+    // 1. Make sure all Aps have set the Present.
+    // 2. Get ready for programming MTRRs.
     //
     WaitForAllAPs (ApCount);
 
@@ -770,12 +772,12 @@ BSPHandler (
   *mSmmMpSyncData->InsideSmm = FALSE;
   ReleaseAllAPs ();
 
-  //
-  // Wait for all APs to complete their pending tasks
-  //
-  WaitForAllAPs (ApCount);
-
   if (SmmCpuFeaturesNeedConfigureMtrrs ()) {
+    //
+    // Wait for all APs to complete their pending tasks
+    //
+    WaitForAllAPs (ApCount);
+
     //
     // Signal APs to restore MTRRs
     //
@@ -791,6 +793,11 @@ BSPHandler (
     // Wait for all APs to complete MTRR programming
     //
     WaitForAllAPs (ApCount);
+
+    //
+    // Signal APs to Reset states/semaphore for this processor
+    //
+    ReleaseAllAPs ();
   }
 
   //
@@ -799,11 +806,6 @@ BSPHandler (
   //
   InitializeDebugAgent (DEBUG_AGENT_INIT_EXIT_SMI, NULL, NULL);
 
-  //
-  // Signal APs to Reset states/semaphore for this processor
-  //
-  ReleaseAllAPs ();
-
   //
   // Perform pending operations for hot-plug
   //
@@ -943,6 +945,8 @@ APHandler (
   if ((SyncMode == SmmCpuSyncModeTradition) || SmmCpuFeaturesNeedConfigureMtrrs ()) {
     //
     // Notify BSP of arrival at this point
+    // 1. Set the Present.
+    // 2. Get ready for programming MTRRs.
     //
     ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);
   }
@@ -1035,17 +1039,17 @@ APHandler (
     //
     SmmCpuFeaturesReenableSmrr ();
     MtrrSetAllMtrrs (&Mtrrs);
-  }
 
-  //
-  // Notify BSP the readiness of this AP to Reset states/semaphore for this processor
-  //
-  ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);
+    //
+    // Notify BSP the readiness of this AP to Reset states/semaphore for this processor
+    //
+    ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);
 
-  //
-  // Wait for the signal from BSP to Reset states/semaphore for this processor
-  //
-  WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);
+    //
+    // Wait for the signal from BSP to Reset states/semaphore for this processor
+    //
+    WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);
+  }
 
   //
   // Reset states/semaphore for this processor