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From: "Laszlo Ersek" <lersek@redhat.com>
To: Damian Nikodem <damian.nikodem@intel.com>, devel@edk2.groups.io
Cc: Eric Dong <eric.dong@intel.com>, Ray Ni <ray.ni@intel.com>,
	Benjamin You <benjamin.you@intel.com>,
	Krzysztof Rusocki <krzysztof.rusocki@intel.com>
Subject: Re: [PATCH v3] UefiCpuPkg: Fix potential spinLock issue in SmmStartupThisAp
Date: Wed, 11 Sep 2019 16:45:53 +0200	[thread overview]
Message-ID: <0cdd6b09-8d44-9aa3-df53-89c69aa7cf80@redhat.com> (raw)
In-Reply-To: <20190911082301.1488-1-damian.nikodem@intel.com>

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@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Benjamin You <benjamin.you@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Krzysztof Rusocki <krzysztof.rusocki@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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  reply	other threads:[~2019-09-11 14:45 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-11  8:23 [PATCH v3] UefiCpuPkg: Fix potential spinLock issue in SmmStartupThisAp Damian Nikodem
2019-09-11 14:45 ` Laszlo Ersek [this message]
2019-09-11 17:37 ` Ni, Ray

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