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

["Song, BinX" <binx.song@intel.com>]

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

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