Re: [Patch 1/3] UefiCpuPkg/RegisterCpuFeaturesLib: Avoid AP calls PeiService.

["Brian J. Johnson" <brian.johnson@hpe.com>]

Agreed.  We've seen issues on real platforms with timed-out spinlocks in 
DXE causing calls to GetPerformanceCounter and DebugAssert.  (DXE has 
the same code, with the same issues.)

Note that it's possible to set PcdSpinLockTimeout=0 to work around the 
issue on a particular platform, or in a particular module.  But if you 
have to do that for every module which uses APs, and hence could contend 
for a spinlock, it kind of defeats the point....  We're better off 
removing the timeout code.

Thanks,
Brian

On 12/19/18 8:08 PM, Yao, Jiewen wrote:
> Yes, I agree, if we don't have any real case.
> 
> 
>> -----Original Message-----
>> From: Ni, Ruiyu
>> Sent: Thursday, December 20, 2018 10:07 AM
>> To: Dong, Eric <eric.dong@intel.com>; Yao, Jiewen
>> <jiewen.yao@intel.com>; edk2-devel@lists.01.org
>> Cc: Laszlo Ersek <lersek@redhat.com>
>> Subject: RE: [edk2] [Patch 1/3] UefiCpuPkg/RegisterCpuFeaturesLib: Avoid
>> AP calls PeiService.
>>
>> Can you just change the AcquireSpinLock() behavior to remove the Timeout
>> PCD consumption?
>>
>> I haven't seen a real case that the timed acquisition of spin lock is needed.
>>
>>
>> Thanks/Ray
>>
>>> -----Original Message-----
>>> From: Dong, Eric <eric.dong@intel.com>
>>> Sent: Thursday, December 20, 2018 9:23 AM
>>> To: Yao, Jiewen <jiewen.yao@intel.com>; edk2-devel@lists.01.org
>>> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Laszlo Ersek <lersek@redhat.com>
>>> Subject: RE: [edk2] [Patch 1/3] UefiCpuPkg/RegisterCpuFeaturesLib: Avoid
>>> AP calls PeiService.
>>>
>>>
>>> Agreed, Maybe it's time to add a new API like
>>> AcquireSpinLockWithoutTimeOut?
>>>
>>> Thanks,
>>> Eric
>>>> -----Original Message-----
>>>> From: Yao, Jiewen
>>>> Sent: Thursday, December 20, 2018 9:19 AM
>>>> To: Dong, Eric <eric.dong@intel.com>; edk2-devel@lists.01.org
>>>> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Laszlo Ersek <lersek@redhat.com>
>>>> Subject: RE: [edk2] [Patch 1/3] UefiCpuPkg/RegisterCpuFeaturesLib:
>>>> Avoid AP calls PeiService.
>>>>
>>>> Hi
>>>> If we think below code is generic, can we have an API for that?
>>>>
>>>> +      //
>>>> +      // Wait for the AP to release the MSR spin lock.
>>>> +      //
>>>> +      while (!AcquireSpinLockOrFail (&CpuFlags->ConsoleLogLock)) {
>>>> +        CpuPause ();
>>>> +      }
>>>>
>>>>
>>>>
>>>>
>>>>> -----Original Message-----
>>>>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf
>>>>> Of Eric Dong
>>>>> Sent: Thursday, December 20, 2018 9:16 AM
>>>>> To: edk2-devel@lists.01.org
>>>>> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Laszlo Ersek <lersek@redhat.com>
>>>>> Subject: [edk2] [Patch 1/3] UefiCpuPkg/RegisterCpuFeaturesLib: Avoid
>>>>> AP calls PeiService.
>>>>>
>>>>> In AcquireSpinLock function, it calls GetPerformanceCounter which
>>>>> final calls PeiService service. This patch avoid to call
>>>>> AcquireSpinLock function.
>>>>>
>>>>> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1411
>>>>>
>>>>> Cc: Ruiyu Ni <ruiyu.ni@intel.com>
>>>>> Cc: Laszlo Ersek <lersek@redhat.com>
>>>>> Contributed-under: TianoCore Contribution Agreement 1.1
>>>>> Signed-off-by: Eric Dong <eric.dong@intel.com>
>>>>> ---
>>>>>   UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c |
>>>>> 7
>>>>> ++++++-
>>>>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git
>>>>> a/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c
>>>>> b/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c
>>>>> index 624ddee055..a64326239f 100644
>>>>> ---
>>>>> a/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c
>>>>> +++
>> b/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.
>>>>> +++ c
>>>>> @@ -832,7 +832,12 @@ ProgramProcessorRegister (
>>>>>       RegisterTableEntry = &RegisterTableEntryHead[Index];
>>>>>
>>>>>       DEBUG_CODE_BEGIN ();
>>>>> -      AcquireSpinLock (&CpuFlags->ConsoleLogLock);
>>>>> +      //
>>>>> +      // Wait for the AP to release the MSR spin lock.
>>>>> +      //
>>>>> +      while (!AcquireSpinLockOrFail (&CpuFlags->ConsoleLogLock)) {
>>>>> +        CpuPause ();
>>>>> +      }
>>>>>         ThreadIndex = ApLocation->Package *
>> CpuStatus->MaxCoreCount *
>>>>> CpuStatus->MaxThreadCount +
>>>>>                 ApLocation->Core * CpuStatus->MaxThreadCount +
>>>>>                 ApLocation->Thread;
>>>>> --
>>>>> 2.15.0.windows.1
>>>>>
>>>>> _______________________________________________
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>>>>> edk2-devel@lists.01.org
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-- 
Brian J. Johnson
Enterprise X86 Lab

Hewlett Packard Enterprise

brian.johnson@hpe.com