UefiCpuPkg/PiSmmCpuDxeSmm: Clarification for BSP & APs Sync Flow

This patch does not impact functionality. It aims to clarify the
synchronization flow between the BSP and APs to enhance code
readability and understanding:

Steps #6 and #11 are the basic synchronization requirements for all
cases.

Steps #1 is additional requirements if the MmCpuSyncModeTradition
mode is selected.

Steps #1, #2, #3, #4, #5, #7, #8, #9, and #10 are additional
requirements if the system needs to configure the MTRR.

Steps #9 and #10 are additional requirements if the system needs to
support the mSmmDebugAgentSupport.

Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>

1 files changed, 22 insertions, 22 deletions

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
index 210b23af21..2df2cb9f22 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
@@ -522,13 +522,13 @@ BSPHandler (
     //

     // Wait for all APs to get ready for programming MTRRs

     //

-    SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex);

+    SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex); /// #1: Wait APs

 

     if (SmmCpuFeaturesNeedConfigureMtrrs ()) {

       //

       // Signal all APs it's time for backup MTRRs

       //

-      ReleaseAllAPs ();

+      ReleaseAllAPs (); /// #2: Signal APs

 

       //

       // SmmCpuSyncWaitForAPs() may wait for ever if an AP happens to enter SMM at

@@ -543,12 +543,12 @@ BSPHandler (
       //

       // Wait for all APs to complete their MTRR saving

       //

-      SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex);

+      SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex); /// #3: Wait APs

 

       //

       // Let all processors program SMM MTRRs together

       //

-      ReleaseAllAPs ();

+      ReleaseAllAPs (); /// #4: Signal APs

 

       //

       // SmmCpuSyncWaitForAPs() may wait for ever if an AP happens to enter SMM at

@@ -560,7 +560,7 @@ BSPHandler (
       //

       // Wait for all APs to complete their MTRR programming

       //

-      SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex);

+      SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex); /// #5: Wait APs

     }

   }

 

@@ -625,18 +625,18 @@ BSPHandler (
   // Notify all APs to exit

   //

   *mSmmMpSyncData->InsideSmm = FALSE;

-  ReleaseAllAPs ();

+  ReleaseAllAPs (); /// #6: Signal APs

 

   if (SmmCpuFeaturesNeedConfigureMtrrs ()) {

     //

     // Wait for all APs the readiness to program MTRRs

     //

-    SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex);

+    SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex); /// #7: Wait APs

 

     //

     // Signal APs to restore MTRRs

     //

-    ReleaseAllAPs ();

+    ReleaseAllAPs (); /// #8: Signal APs

 

     //

     // Restore OS MTRRs

@@ -649,12 +649,12 @@ BSPHandler (
     //

     // Wait for all APs to complete their pending tasks including MTRR programming if needed.

     //

-    SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex);

+    SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex); /// #9: Wait APs

 

     //

     // Signal APs to Reset states/semaphore for this processor

     //

-    ReleaseAllAPs ();

+    ReleaseAllAPs (); /// #10: Signal APs

   }

 

   if (mSmmDebugAgentSupport) {

@@ -679,7 +679,7 @@ BSPHandler (
   // Gather APs to exit SMM synchronously. Note the Present flag is cleared by now but

   // WaitForAllAps does not depend on the Present flag.

   //

-  SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex);

+  SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex); /// #11: Wait APs

 

   //

   // At this point, all APs should have exited from APHandler().

@@ -805,14 +805,14 @@ APHandler (
     //

     // Notify BSP of arrival at this point

     //

-    SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);

+    SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #1: Signal BSP

   }

 

   if (SmmCpuFeaturesNeedConfigureMtrrs ()) {

     //

     // Wait for the signal from BSP to backup MTRRs

     //

-    SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);

+    SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #2: Wait BSP

 

     //

     // Backup OS MTRRs

@@ -822,12 +822,12 @@ APHandler (
     //

     // Signal BSP the completion of this AP

     //

-    SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);

+    SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #3: Signal BSP

 

     //

     // Wait for BSP's signal to program MTRRs

     //

-    SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);

+    SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #4: Wait BSP

 

     //

     // Replace OS MTRRs with SMI MTRRs

@@ -837,14 +837,14 @@ APHandler (
     //

     // Signal BSP the completion of this AP

     //

-    SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);

+    SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #5: Signal BSP

   }

 

   while (TRUE) {

     //

     // Wait for something to happen

     //

-    SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);

+    SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #6: Wait BSP

 

     //

     // Check if BSP wants to exit SMM

@@ -884,12 +884,12 @@ APHandler (
     //

     // Notify BSP the readiness of this AP to program MTRRs

     //

-    SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);

+    SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #7: Signal BSP

 

     //

     // Wait for the signal from BSP to program MTRRs

     //

-    SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);

+    SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #8: Wait BSP

 

     //

     // Restore OS MTRRs

@@ -902,12 +902,12 @@ APHandler (
     //

     // Notify BSP the readiness of this AP to Reset states/semaphore for this processor

     //

-    SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);

+    SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #9: Signal BSP

 

     //

     // Wait for the signal from BSP to Reset states/semaphore for this processor

     //

-    SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);

+    SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #10: Wait BSP

   }

 

   //

@@ -918,7 +918,7 @@ APHandler (
   //

   // Notify BSP the readiness of this AP to exit SMM

   //

-  SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);

+  SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #11: Signal BSP

 }

 

 /**