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UefiCpuPkg/PiSmmCpuDxeSmm: Clarification for BSP & APs Sync Flow
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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 tianocore#6 and tianocore#11 are the basic synchronization requirements for all
cases.

Steps tianocore#1 and tianocore#2 are additional requirements if the
MmCpuSyncModeTradition mode is selected.

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

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

Signed-off-by: Jiaxin Wu <[email protected]>
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@jiaxinwu
jiaxinwu committed Oct 12, 2024
1 parent f7cf7d5 commit d42b2bf
Showing 1 changed file with 22 additions and 22 deletions.
44 changes: 22 additions & 22 deletions UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
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Original file line number Diff line number Diff line change
Expand Up @@ -522,14 +522,14 @@ BSPHandler (
//
// Wait for all APs of arrival at this point
//
SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex);
SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex); /// #1: Wait APs

//
// Signal all APs it's time for:
// 1. Backup MTRRs if needed.
// 2. Perform SMM CPU Platform Hook before executing MMI Handler.
//
ReleaseAllAPs ();
ReleaseAllAPs (); /// #2: Signal APs

if (SmmCpuFeaturesNeedConfigureMtrrs ()) {
//
Expand All @@ -545,12 +545,12 @@ 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
Expand All @@ -562,7 +562,7 @@ BSPHandler (
//
// Wait for all APs to complete their MTRR programming
//
SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex);
SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount, CpuIndex); /// #5: Wait APs
}
}

Expand Down Expand Up @@ -632,18 +632,18 @@ 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
Expand All @@ -656,12 +656,12 @@ 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) {
Expand All @@ -686,7 +686,7 @@ 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().
Expand Down Expand Up @@ -812,14 +812,14 @@ APHandler (
//
// Notify BSP of arrival at this point
//
SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);
SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #1: Signal BSP

//
// Wait for the signal from BSP to:
// 1. Backup MTRRs if needed.
// 2. Perform SMM CPU Platform Hook before executing MMI Handler.
//
SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);
SmmCpuSyncWaitForBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #2: Wait BSP
}

if (SmmCpuFeaturesNeedConfigureMtrrs ()) {
Expand All @@ -831,12 +831,12 @@ 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
Expand All @@ -846,7 +846,7 @@ APHandler (
//
// Signal BSP the completion of this AP
//
SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);
SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #5: Signal BSP
}

//
Expand All @@ -858,7 +858,7 @@ APHandler (
//
// 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
Expand Down Expand Up @@ -898,12 +898,12 @@ 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
Expand All @@ -916,12 +916,12 @@ 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
}

//
Expand All @@ -932,7 +932,7 @@ APHandler (
//
// Notify BSP the readiness of this AP to exit SMM
//
SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex);
SmmCpuSyncReleaseBsp (mSmmMpSyncData->SyncContext, CpuIndex, BspIndex); /// #11: Signal BSP
}

/**
Expand Down

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