Re: [edk2-devel] [PATCH v2 4/6] UefiCpuPkg/PiSmmCpuDxeSmm: Align BSP and AP sync logic for SMI exit

["Ni, Ray" <ray.ni@intel.com>]

Reviewed-by: Ray Ni <ray.ni@Intel.com>

Thanks,
Ray
> -----Original Message-----
> From: Wu, Jiaxin <jiaxin.wu@intel.com>
> Sent: Tuesday, December 26, 2023 12:21 AM
> To: devel@edk2.groups.io
> Cc: Laszlo Ersek <lersek@redhat.com>; Dong, Eric <eric.dong@intel.com>; Ni,
> Ray <ray.ni@intel.com>; Zeng, Star <star.zeng@intel.com>; Gerd Hoffmann
> <kraxel@redhat.com>; Kumar, Rahul R <rahul.r.kumar@intel.com>
> Subject: [PATCH v2 4/6] UefiCpuPkg/PiSmmCpuDxeSmm: Align BSP and AP
> sync logic for SMI exit
> 
> Below piece of code is the BSP and AP sync logic for SMI exit.
> 1. AP after finish the scheduled procedure:
>   if (SmmCpuFeaturesNeedConfigureMtrrs ()) {
>     SmmCpuSyncReleaseBsp ();
>     SmmCpuSyncWaitForBsp ();
>     ...
>   }
>   SmmCpuSyncReleaseBsp ();
>   SmmCpuSyncWaitForBsp ();
>   SmmCpuSyncReleaseBsp ();
> 
> 2. BSP after return from SmmCoreEntry:
>   SmmCpuSyncWaitForAPs ();
>   if (SmmCpuFeaturesNeedConfigureMtrrs ()) {
>     ReleaseAllAPs ();
>     ...
>     SmmCpuSyncWaitForAPs ();
>   }
>   ReleaseAllAPs ();
>   SmmCpuSyncWaitForAPs();
> 
> This patch is to make BSP same as AP sync logic:
>   if (SmmCpuFeaturesNeedConfigureMtrrs ()) {
>     SmmCpuSyncWaitForAPs ();
>     ReleaseAllAPs ();
>     ...
>   }
>   SmmCpuSyncWaitForAPs ();
>   ReleaseAllAPs ();
>   SmmCpuSyncWaitForAPs();
> 
> With the change, it will be easy to understand the sync flow as
> below:
> BSP: SmmCpuSyncWaitForAPs  <--  AP: SmmCpuSyncReleaseBsp
> BSP: ReleaseAllAPs         -->  AP: SmmCpuSyncWaitForBsp
> 
> This patch doesn't have function impact.
> 
> 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: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> index 324e85d6b5..bd2c9f841b 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> @@ -625,33 +625,33 @@ BSPHandler (
>    // Notify all APs to exit
>    //
>    *mSmmMpSyncData->InsideSmm = FALSE;
>    ReleaseAllAPs ();
> 
> -  //
> -  // Wait for all APs to complete their pending tasks
> -  //
> -  SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount,
> CpuIndex);
> -
>    if (SmmCpuFeaturesNeedConfigureMtrrs ()) {
> +    //
> +    // Wait for all APs the readiness to program MTRRs
> +    //
> +    SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount,
> CpuIndex);
> +
>      //
>      // Signal APs to restore MTRRs
>      //
>      ReleaseAllAPs ();
> 
>      //
>      // Restore OS MTRRs
>      //
>      SmmCpuFeaturesReenableSmrr ();
>      MtrrSetAllMtrrs (&Mtrrs);
> -
> -    //
> -    // Wait for all APs to complete MTRR programming
> -    //
> -    SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount,
> CpuIndex);
>    }
> 
> +  //
> +  // Wait for all APs to complete their pending tasks including MTRR
> programming if needed.
> +  //
> +  SmmCpuSyncWaitForAPs (mSmmMpSyncData->SyncContext, ApCount,
> CpuIndex);
> +
>    if (mSmmDebugAgentSupport) {
>      //
>      // Stop source level debug in BSP handler, the code below will not be
>      // debugged.
>      //
> --
> 2.16.2.windows.1



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