For SMM CPU semaphore sync, there is no need atomic semaphore
operation, just use the flag to indicate it has complete the
wait/release. Based on this, this patch is to refine 2 functions
(WaitForAllAPs & ReleaseAllAPs) and define 2 new functions
(WaitForBsp & ReleaseBsp) used for the semaphore sync between
BSP & AP.
Sync flow like below:
1. BSP to Release All APs ---> 1. AP to Wait BSP
ReleaseAllAPs () WaitForBsp
2. BSP to Wait All APs <--- 2. AP to Release BSP
WaitForAllAPs () ReleaseBsp
With this change, SMM CPU semaphore sync for SMI exit performance
will be significant improved.
Cc: Eric Dong <eric.d...@intel.com>
Cc: Ray Ni <ray...@intel.com>
Cc: Zeng Star <star.z...@intel.com>
Cc: Rahul Kumar <rahul1.ku...@intel.com>
Cc: Gerd Hoffmann <kra...@redhat.com>
Signed-off-by: Jiaxin Wu <jiaxin...@intel.com>
---
UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 68 ++++++++++++++++++++++++++---------
1 file changed, 51 insertions(+), 17 deletions(-)
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
index 25d058c5b9..0bf460e81c 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
@@ -120,11 +120,11 @@ LockdownSemaphore (
return Value;
}
/**
- Wait all APs to performs an atomic compare exchange operation to release
semaphore.
+ Used for BSP to wait all APs.
@param NumberOfAPs AP number
**/
VOID
@@ -133,18 +133,19 @@ WaitForAllAPs (
)
{
UINTN BspIndex;
BspIndex = mSmmMpSyncData->BspIndex;
- while (NumberOfAPs-- > 0) {
- WaitForSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);
+ while (NumberOfAPs != *mSmmMpSyncData->CpuData[BspIndex].Run) {
+ CpuPause ();
}
+
+ *mSmmMpSyncData->CpuData[BspIndex].Run = 0;
}
/**
- Performs an atomic compare exchange operation to release semaphore
- for each AP.
+ Used for BSP to release all APs.
**/
VOID
ReleaseAllAPs (
VOID
@@ -152,15 +153,48 @@ ReleaseAllAPs (
{
UINTN Index;
for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
if (IsPresentAp (Index)) {
- ReleaseSemaphore (mSmmMpSyncData->CpuData[Index].Run);
+ ASSERT (*mSmmMpSyncData->CpuData[Index].Run == 0);
+ *mSmmMpSyncData->CpuData[Index].Run = 1;
}
}
}
+/**
+ Used for Ap to wait BSP.
+
+ @param ApSem IN: 32-bit unsigned integer
+ OUT: original integer 0
+**/
+VOID
+WaitForBsp (
+ IN OUT volatile UINT32 *ApSem
+ )
+{
+ while (*ApSem == 0) {
+ CpuPause ();
+ }
+
+ *ApSem = 0;
+}
+
+/**
+ Used for Ap to release BSP.
+
+ @param BspSem IN: 32-bit unsigned integer
+ OUT: original integer + 1
+**/
+VOID
+ReleaseBsp (
+ IN OUT volatile UINT32 *BspSem
+ )
+{
+ InterlockedIncrement (BspSem);
+}
+
/**
Check whether the index of CPU perform the package level register
programming during System Management Mode initialization.
The index of Processor specified by mPackageFirstThreadIndex[PackageIndex]
@@ -898,50 +932,50 @@ APHandler (
if ((SyncMode == SmmCpuSyncModeTradition) ||
SmmCpuFeaturesNeedConfigureMtrrs ()) {
//
// 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
//
MtrrGetAllMtrrs (&Mtrrs);
//
// 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
//
ReplaceOSMtrrs (CpuIndex);
//
// 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
//
if (!(*mSmmMpSyncData->InsideSmm)) {
@@ -977,16 +1011,16 @@ APHandler (
if (SmmCpuFeaturesNeedConfigureMtrrs ()) {
//
// 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
//
SmmCpuFeaturesReenableSmrr ();
@@ -994,26 +1028,26 @@ 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
//
*(mSmmMpSyncData->CpuData[CpuIndex].Present) = FALSE;
//
// Notify BSP the readiness of this AP to exit SMM
//
- ReleaseSemaphore (mSmmMpSyncData->CpuData[BspIndex].Run);
+ ReleaseBsp (mSmmMpSyncData->CpuData[BspIndex].Run);
}
/**
Checks whether the input token is the current used token.
--
2.16.2.windows.1
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