UefiCpuPkg/PiSmmCpuDxeSmm: Optimize Semaphore Sync between BSP and AP

This patch is to define 3 new functions (WaitForBsp & ReleaseBsp &
ReleaseOneAp) used for the semaphore sync between BSP & AP. With the
change, BSP and AP Sync flow will be easy understand as below:
BSP: ReleaseAllAPs or ReleaseOneAp --> AP: WaitForBsp
BSP: WaitForAllAPs                 <-- AP: ReleaseBsp

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Zeng Star <star.zeng@intel.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>

1 files changed, 58 insertions, 14 deletions

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
index b279f5dfcc..54542262a2 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
@@ -122,6 +122,7 @@ LockdownSemaphore (
 }

 

 /**

+  Used for BSP to wait all APs.

   Wait all APs to performs an atomic compare exchange operation to release semaphore.

 

   @param   NumberOfAPs      AP number

@@ -141,6 +142,7 @@ WaitForAllAPs (
 }

 

 /**

+  Used for BSP to release all APs.

   Performs an atomic compare exchange operation to release semaphore

   for each AP.

 

@@ -160,6 +162,48 @@ ReleaseAllAPs (
 }

 

 /**

+  Used for BSP to release one AP.

+

+  @param      ApSem     IN:  32-bit unsigned integer

+                        OUT: original integer + 1

+**/

+VOID

+ReleaseOneAp   (

+  IN OUT  volatile UINT32  *ApSem

+  )

+{

+  ReleaseSemaphore (ApSem);

+}

+

+/**

+  Used for AP to wait BSP.

+

+  @param      ApSem      IN:  32-bit unsigned integer

+                         OUT: original integer - 1

+**/

+VOID

+WaitForBsp  (

+  IN OUT  volatile UINT32  *ApSem

+  )

+{

+  WaitForSemaphore (ApSem);

+}

+

+/**

+  Used for AP to release BSP.

+

+  @param      BspSem     IN:  32-bit unsigned integer

+                         OUT: original integer + 1

+**/

+VOID

+ReleaseBsp   (

+  IN OUT  volatile UINT32  *BspSem

+  )

+{

+  ReleaseSemaphore (BspSem);

+}

+

+/**

   Check whether the index of CPU perform the package level register

   programming during System Management Mode initialization.

 

@@ -634,7 +678,7 @@ BSPHandler (
       ReleaseAllAPs ();

 

       //

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

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

       // exactly this point. Please make sure PcdCpuSmmMaxSyncLoops has been set

       // to a large enough value to avoid this situation.

       // Note: For HT capable CPUs, threads within a core share the same set of MTRRs.

@@ -654,7 +698,7 @@ BSPHandler (
       ReleaseAllAPs ();

 

       //

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

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

       // exactly this point. Please make sure PcdCpuSmmMaxSyncLoops has been set

       // to a large enough value to avoid this situation.

       //

@@ -900,14 +944,14 @@ APHandler (
     //

     // Notify BSP of arrival at this point

     //

-    ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);

+    ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);

   }

 

   if (SmmCpuFeaturesNeedConfigureMtrrs ()) {

     //

     // Wait for the signal from BSP to backup MTRRs

     //

-    WaitForSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);

+    WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);

 

     //

     // Backup OS MTRRs

@@ -917,12 +961,12 @@ APHandler (
     //

     // Signal BSP the completion of this AP

     //

-    ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);

+    ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);

 

     //

     // Wait for BSP's signal to program MTRRs

     //

-    WaitForSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);

+    WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);

 

     //

     // Replace OS MTRRs with SMI MTRRs

@@ -932,14 +976,14 @@ APHandler (
     //

     // Signal BSP the completion of this AP

     //

-    ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);

+    ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);

   }

 

   while (TRUE) {

     //

     // Wait for something to happen

     //

-    WaitForSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);

+    WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);

 

     //

     // Check if BSP wants to exit SMM

@@ -979,12 +1023,12 @@ APHandler (
     //

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

     //

-    ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);

+    ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);

 

     //

     // Wait for the signal from BSP to program MTRRs

     //

-    WaitForSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);

+    WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);

 

     //

     // Restore OS MTRRs

@@ -996,12 +1040,12 @@ APHandler (
   //

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

   //

-  ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);

+  ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);

 

   //

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

   //

-  WaitForSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);

+  WaitForBsp (mSmmMpSyncData->CpuData[CpuIndex].Run);

 

   //

   // Reset states/semaphore for this processor

@@ -1011,7 +1055,7 @@ APHandler (
   //

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

   //

-  ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);

+  ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);

 }

 

 /**

@@ -1279,7 +1323,7 @@ InternalSmmStartupThisAp (
     *mSmmMpSyncData->CpuData[CpuIndex].Status = EFI_NOT_READY;

   }

 

-  ReleaseSemaphore (mSmmMpSyncData->CpuData[CpuIndex].Run);

+  ReleaseOneAp (mSmmMpSyncData->CpuData[CpuIndex].Run);

 

   if (Token == NULL) {

     AcquireSpinLock (mSmmMpSyncData->CpuData[CpuIndex].Busy);