Re: [PATCH] UefiCpuPkg: Enhance CPU feature dependency check

[Laszlo Ersek <lersek@redhat.com>]

On 02/01/18 03:09, Song, BinX wrote:
> Hi Laszlo,
> 
> Thanks for your comments.
> Explain the issue first:
> In CpuCommonFeaturesLib.inf -> CpuCommonFeaturesLib.c -> CpuCommonFeaturesLibConstructor() function,
> it invokes RegisterCpuFeature() to register CPU feature. Some original source codes is here.
>   if (IsCpuFeatureSupported (CPU_FEATURE_AESNI)) {
>     Status = RegisterCpuFeature (
>                "AESNI",
>                AesniGetConfigData,
>                AesniSupport,
>                AesniInitialize,
>                CPU_FEATURE_AESNI,
>                CPU_FEATURE_END
>                );
>     ASSERT_EFI_ERROR (Status);
>   }
>   if (IsCpuFeatureSupported (CPU_FEATURE_MWAIT)) {
>     Status = RegisterCpuFeature (
>                "MWAIT",
>                NULL,
>                MonitorMwaitSupport,
>                MonitorMwaitInitialize,
>                CPU_FEATURE_MWAIT,
>                CPU_FEATURE_END
>                );
>     ASSERT_EFI_ERROR (Status);
>   }
> 
> Then I update them to below.
>   if (IsCpuFeatureSupported (CPU_FEATURE_AESNI)) {
>     Status = RegisterCpuFeature (
>                "AESNI",
>                AesniGetConfigData,
>                AesniSupport,
>                AesniInitialize,
>                CPU_FEATURE_AESNI,
>                CPU_FEATURE_MWAIT | CPU_FEATURE_BEFORE,
>                CPU_FEATURE_END
>                );
>     ASSERT_EFI_ERROR (Status);
>   }
>   if (IsCpuFeatureSupported (CPU_FEATURE_MWAIT)) {
>     Status = RegisterCpuFeature (
>                "MWAIT",
>                NULL,
>                MonitorMwaitSupport,
>                MonitorMwaitInitialize,
>                CPU_FEATURE_MWAIT,
>                CPU_FEATURE_AESNI | CPU_FEATURE_BEFORE,
>                CPU_FEATURE_END
>                );
>     ASSERT_EFI_ERROR (Status);
>   }
> Original function CheckCpuFeaturesDependency() will enter a dead loop and prompt nothing when checking and sorting them.

Ah, I see, so the RegisterCpuFeature() call can add before/after hints
to the features. And circular dependencies cause an infinite loop currently.

> I think a better way is to detect this conflicted logic and give some hints to user, then assert(false).
> 
> For your three comments.
> 1. How about change to this?
>   if (BeforeFlag) {
>     DEBUG ((DEBUG_ERROR, "Error: Feature %a before condition is invalid!", CurrentCpuFeature->FeatureName));
>   } else {
>     DEBUG ((DEBUG_ERROR, "Error: Feature %a after condition is invalid!", CurrentCpuFeature->FeatureName));
>   }

It's OK to do this as well:

  DEBUG ((
    DEBUG_ERROR,
    "Error: Feature %a %a condition is invalid!\n",
    CurrentCpuFeature->FeatureName,
    BeforeFlag ? "before" : "after"
    ));

> 2. Will update it in V2 patch.
> 3. How about add a prefix before the name? RegisterCpuFeaturesLibSortCpuFeatures() will be unique.

Sure.

Thanks!
Laszlo

> 
> Best Regards,
> Bell Song
> 
>> -----Original Message-----
>> From: Laszlo Ersek [mailto:lersek@redhat.com]
>> Sent: Wednesday, January 31, 2018 5:44 PM
>> To: Song, BinX <binx.song@intel.com>; edk2-devel@lists.01.org
>> Cc: Dong, Eric <eric.dong@intel.com>
>> Subject: Re: [PATCH] UefiCpuPkg: Enhance CPU feature dependency check
>>
>> On 01/31/18 08:00, Song, BinX wrote:
>>> Current CPU feature dependency check will hang on when meet below or
>>> similar case:
>>> if (IsCpuFeatureSupported (CPU_FEATURE_AESNI)) {
>>>   Status = RegisterCpuFeature (
>>>              "AESNI",
>>>              AesniGetConfigData,
>>>              AesniSupport,
>>>              AesniInitialize,
>>>              CPU_FEATURE_AESNI,
>>>              CPU_FEATURE_MWAIT | CPU_FEATURE_BEFORE,
>>>              CPU_FEATURE_END
>>>              );
>>>   ASSERT_EFI_ERROR (Status);
>>> }
>>> if (IsCpuFeatureSupported (CPU_FEATURE_MWAIT)) {
>>>   Status = RegisterCpuFeature (
>>>              "MWAIT",
>>>              NULL,
>>>              MonitorMwaitSupport,
>>>              MonitorMwaitInitialize,
>>>              CPU_FEATURE_MWAIT,
>>>              CPU_FEATURE_AESNI | CPU_FEATURE_BEFORE,
>>>              CPU_FEATURE_END
>>>              );
>>>   ASSERT_EFI_ERROR (Status);
>>> }
>>>
>>> Solution is to separate current CPU feature dependency check into
>>> sort and check two parts.
>>>
>>> Sort function:
>>> According to CPU feature's dependency, sort all CPU features.
>>> Later dependency will override previous dependency if they are conflicted.
>>>
>>> Check function:
>>> Check sorted CPU features' relationship, ASSERT invalid relationship.
>>>
>>> Cc: Eric Dong <eric.dong@intel.com>
>>> Cc: Laszlo Ersek <lersek@redhat.com>
>>> Contributed-under: TianoCore Contribution Agreement 1.1
>>> Signed-off-by: Bell Song <binx.song@intel.com>
>>> ---
>>>  .../RegisterCpuFeaturesLib/CpuFeaturesInitialize.c | 271
>> ++++++++++++++++++++-
>>>  .../RegisterCpuFeaturesLib/RegisterCpuFeatures.h   |   7 +
>>>  .../RegisterCpuFeaturesLib.c                       | 130 +---------
>>>  3 files changed, 278 insertions(+), 130 deletions(-)
>>>
>>> diff --git
>> a/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c
>> b/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c
>>> index 4d75c07..2fd0d5f 100644
>>> --- a/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c
>>> +++ b/UefiCpuPkg/Library/RegisterCpuFeaturesLib/CpuFeaturesInitialize.c
>>> @@ -423,6 +423,271 @@ DumpRegisterTableOnProcessor (
>>>  }
>>>
>>>  /**
>>> +  From FeatureBitMask, find the right feature entry in CPU feature list.
>>> +
>>> +  @param[in]  FeatureList    The pointer to CPU feature list.
>>> +  @param[in]  CurrentFeature The pointer to current CPU feature.
>>> +  @param[in]  BeforeFlag     TRUE: BeforeFeatureBitMask; FALSE:
>> AfterFeatureBitMask.
>>> +
>>> +  @return  The pointer to right CPU feature entry.
>>> +**/
>>> +LIST_ENTRY *
>>> +FindFeatureInList(
>>> +  IN LIST_ENTRY              *CpuFeatureList,
>>> +  IN CPU_FEATURES_ENTRY      *CurrentCpuFeature,
>>> +  IN BOOLEAN                  BeforeFlag
>>> +  )
>>> +{
>>> +  LIST_ENTRY                 *TempEntry;
>>> +  CPU_FEATURES_ENTRY         *TempFeature;
>>> +  UINT8                      *FeatureBitMask;
>>> +
>>> +  FeatureBitMask = BeforeFlag ? CurrentCpuFeature-
>>> BeforeFeatureBitMask : CurrentCpuFeature->AfterFeatureBitMask;
>>> +  TempEntry = GetFirstNode (CpuFeatureList);
>>> +  while (!IsNull (CpuFeatureList, TempEntry)) {
>>> +    TempFeature = CPU_FEATURE_ENTRY_FROM_LINK (TempEntry);
>>> +    if (IsBitMaskMatchCheck (FeatureBitMask, TempFeature-
>>> FeatureMask)){
>>> +      return TempEntry;
>>> +    }
>>> +    TempEntry = TempEntry->ForwardLink;
>>> +  }
>>> +
>>> +  DEBUG ((DEBUG_ERROR, "Error: Feature %a ", CurrentCpuFeature-
>>> FeatureName, BeforeFlag ? "before ":"after ", "condition is invalid!\n"));
>>
>> Hi, I skimmed this patch quickly -- I can tell that I can't really tell
>> what's going on. I don't know how the feature dependencies are defined
>> in the first place, and what the bug is.
>>
>> However, I do see that the above DEBUG macro invocation is incorrect.
>> The format string has one (1) %a conversion specification, but we pass
>> three (3) arguments.
>>
>> I think the last argument ("condition is invalid!\n") should actually be
>> part of the format string. And then, the "before"/"after" string has to
>> be printed somehow as well.
>>
>> Another superficial observation below:
>>
>>> +/**
>>> +  Check sorted CPU features' relationship, ASSERT invalid one.
>>> +
>>> +  @param[in]  FeatureList  The pointer to CPU feature list.
>>> +**/
>>> +VOID
>>> +CheckCpuFeaturesRelationShip (
>>
>> I don't think we should capitalize "Ship" in this identifier.
>>
>> Third comment: there are several ways to define "sorting", so I'm not
>> sure my question applies, but: can we replace the manual sorting with
>> SortLib?
>>
>> Thanks
>> Laszlo