[edk2-devel] [PATCH v3] UefiCpuPkg: Fix potential spinLock issue in SmmStartupThisAp

[Laszlo Ersek]

On 09/11/19 10:23, Damian Nikodem wrote:
> Due to needs a tackling the deficiency of the AP API, is necessary to ensure that in non-blocking mode
> previous AP executed command is finished before start new one. 
> 
> To remedy above: 
>   1) execute AcquireSpinLock instead AcquireSpinLockOrFail - this will ensure time "window" to eliminate potential
>      race condition beetwen BSP and AP spinLock release in non-blocking mode.
>      This also will eliminate possibility to start executing new AP function before last is finished.
>   2) remove returns EFI_STATUS - EFI_NOT_READY - in new scenario returned status is not necessary to caller.
> 
> Signed-off-by: Damian Nikodem <damian.nikodem at intel.com>
> Cc: Eric Dong <eric.dong at intel.com>
> Cc: Ray Ni <ray.ni at intel.com>
> Cc: Benjamin You <benjamin.you at intel.com>
> Cc: Laszlo Ersek <lersek at redhat.com>
> Cc: Krzysztof Rusocki <krzysztof.rusocki at intel.com>

Eric, Ray, please don't wait for my feedback on this one. It would be
prudent for me to test this, but I got no time.

Thanks
Laszlo

> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> index d8d2b6f444..0685637c2b 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> @@ -1235,14 +1235,9 @@ InternalSmmStartupThisAp (
>      return EFI_INVALID_PARAMETER;
>    }
>  
> -  if (Token == NULL) {
> -    AcquireSpinLock (mSmmMpSyncData->CpuData[CpuIndex].Busy);
> -  } else {
> -    if (!AcquireSpinLockOrFail (mSmmMpSyncData->CpuData[CpuIndex].Busy)) {
> -      DEBUG((DEBUG_ERROR, "Can't acquire mSmmMpSyncData->CpuData[%d].Busy\n", CpuIndex));
> -      return EFI_NOT_READY;
> -    }
> +  AcquireSpinLock (mSmmMpSyncData->CpuData[CpuIndex].Busy);
>  
> +  if (Token != NULL) {
>      *Token = (MM_COMPLETION) CreateToken ();
>    }
> --------------------------------------------------------------------
> 
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