Re: [edk2-devel] [Patch V3] UefiCpuPkg/PiSmmCpuDxeSmm: SmmCpuRendezvous ensure all Aps in Present.

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

Yuanhao, Zhihao,
Can you kindly explain a bit more about this sentence in commit message " SMM read save state requires AP must be present."?

Thanks,
Ray
> -----Original Message-----
> From: Xie, Yuanhao <yuanhao.xie@intel.com>
> Sent: Friday, December 15, 2023 5:30 PM
> To: devel@edk2.groups.io
> Cc: Xie, Yuanhao <yuanhao.xie@intel.com>; Li, Zhihao <zhihao.li@intel.com>;
> Ni, Ray <ray.ni@intel.com>; Kumar, Rahul R <rahul.r.kumar@intel.com>; Gerd
> Hoffmann <kraxel@redhat.com>; Wu, Jiaxin <jiaxin.wu@intel.com>
> Subject: [Patch V3] UefiCpuPkg/PiSmmCpuDxeSmm: SmmCpuRendezvous
> ensure all Aps in Present.
> 
> SMM read save state requires AP must be present.
> This patch aim to avoid the AP not ready for save state check.
> Furthermore, SmmWaitForApArrival has two callers: SmmCpuRendezvous and
> BSPHandler, the behavior of the two callers can be consistent by add
> the while loop to check the present of the APs to SmmCpuRendezvous.
> 
> Signed-off-by: Zhihao Li <zhihao.li@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Jiaxin Wu <jiaxin.wu@intel.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/CpuService.c     | 27
> +++++++++++++++++++++++++++
>  UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h | 13 +++++++++++++
>  2 files changed, 40 insertions(+)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuService.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuService.c
> index c0485b0519..3e98955319 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuService.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuService.c
> @@ -416,8 +416,15 @@ SmmCpuRendezvous (
>    IN BOOLEAN                            BlockingMode
>    )
>  {
> +  UINTN       Index;
> +  UINTN       PresentCount;
> +  UINT32      BlockedCount;
> +  UINT32      DisabledCount;
>    EFI_STATUS  Status;
> 
> +  BlockedCount  = 0;
> +  DisabledCount = 0;
> +
>    //
>    // Return success immediately if all CPUs are already synchronized.
>    //
> @@ -436,6 +443,26 @@ SmmCpuRendezvous (
>      // There are some APs outside SMM, Wait for all avaiable APs to arrive.
>      //
>      SmmWaitForApArrival ();
> +
> +    //
> +    // Make sure all APs have their Present flag set
> +    //
> +    while (TRUE) {
> +      PresentCount = 0;
> +      for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
> +        if (*(mSmmMpSyncData->CpuData[Index].Present)) {
> +          PresentCount++;
> +        }
> +      }
> +
> +      GetSmmDelayedBlockedDisabledCount (NULL, &BlockedCount,
> &DisabledCount);
> +      if (PresentCount == mMaxNumberOfCpus - BlockedCount -
> DisabledCount ) {
> +        break;
> +      }
> +
> +      CpuPause ();
> +    }
> +
>      Status = mSmmMpSyncData->AllApArrivedWithException ?
> EFI_SUCCESS : EFI_TIMEOUT;
>    } else {
>      //
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> index f18345881b..e3538957fb 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> @@ -1552,6 +1552,19 @@ SmmWaitForApArrival (
>    VOID
>    );
> 
> +/**
> +  Returns the Number of SMM Delayed & Blocked & Disabled Thread Count.
> +  @param[in,out] DelayedCount  The Number of SMM Delayed Thread
> Count.
> +  @param[in,out] BlockedCount  The Number of SMM Blocked Thread
> Count.
> +  @param[in,out] DisabledCount The Number of SMM Disabled Thread
> Count.
> +**/
> +VOID
> +GetSmmDelayedBlockedDisabledCount (
> +  IN OUT UINT32  *DelayedCount,
> +  IN OUT UINT32  *BlockedCount,
> +  IN OUT UINT32  *DisabledCount
> +  );
> +
>  /**
>    Write unprotect read-only pages if Cr0.Bits.WP is 1.
> 
> --
> 2.39.1.windows.1



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