Re: [edk2-devel] [PATCH] UefiCpuPkg CpuCommonFeaturesLib: Remove CPU generation check

["Zeng, Star" <star.zeng@intel.com>]

Thanks for the understanding to all of you.


Star
> -----Original Message-----
> From: Ni, Ray
> Sent: Friday, May 17, 2019 9:11 PM
> To: Zeng, Star <star.zeng@intel.com>; devel@edk2.groups.io;
> lersek@redhat.com
> Cc: Dong, Eric <eric.dong@intel.com>; Kumar, Chandana C
> <chandana.c.kumar@intel.com>; Li, Kevin Y <kevin.y.li@intel.com>
> Subject: RE: [edk2-devel] [PATCH] UefiCpuPkg CpuCommonFeaturesLib:
> Remove CPU generation check
> 
> Star,
> I understand the motivation of the change.
> 
> Given your statement that all processors you met follows the rule, and I
> know that you are currently working very actively on Intel processors,
> Reviewed-by: Ray Ni <ray.ni@intel.com>
> 
> > -----Original Message-----
> > From: Zeng, Star
> > Sent: Friday, May 17, 2019 11:05 AM
> > To: Ni, Ray <ray.ni@intel.com>; devel@edk2.groups.io;
> > lersek@redhat.com
> > Cc: Dong, Eric <eric.dong@intel.com>; Kumar, Chandana C
> > <chandana.c.kumar@intel.com>; Li, Kevin Y <kevin.y.li@intel.com>;
> > Zeng, Star <star.zeng@intel.com>
> > Subject: RE: [edk2-devel] [PATCH] UefiCpuPkg CpuCommonFeaturesLib:
> > Remove CPU generation check
> >
> > Situation: All the generations (including the internal generations not
> > listed in
> > SDM) we saw have MSR 13Ch available when CpuInfo-
> > >CpuIdVersionInfoEcx.Bits.AESNI == 1.
> >
> > Requirement: Reuse more code.
> >
> > Could you help think the good method and even propose the patch for that?
> > I am ok to any method to improve the code's reusability.
> > Otherwise, we can only use function level override method ina
> > CpuSpecificFeaturesLib.
> >     Status = RegisterCpuFeature (
> >                "AESNI",
> >                NULL,                                         // Use core function
> >                SpecificAesniSupport,                         // Override core function
> >                NULL,                                         // Use core function
> >                CPU_FEATURE_AESNI,
> >                CPU_FEATURE_END
> >                );
> >
> > Thanks,
> > Star
> > > -----Original Message-----
> > > From: Ni, Ray
> > > Sent: Friday, May 17, 2019 9:04 AM
> > > To: Zeng, Star <star.zeng@intel.com>; devel@edk2.groups.io;
> > > lersek@redhat.com
> > > Cc: Dong, Eric <eric.dong@intel.com>; Kumar, Chandana C
> > > <chandana.c.kumar@intel.com>
> > > Subject: RE: [edk2-devel] [PATCH] UefiCpuPkg CpuCommonFeaturesLib:
> > > Remove CPU generation check
> > >
> > > Star,
> > > I think the discussion is about providing the evidence to support
> > > removing the generation check.
> > > Not just the benefit of that.
> > >
> > > Thanks,
> > > Ray
> > >
> > > > -----Original Message-----
> > > > From: Zeng, Star
> > > > Sent: Thursday, May 16, 2019 10:52 PM
> > > > To: devel@edk2.groups.io; lersek@redhat.com
> > > > Cc: Dong, Eric <eric.dong@intel.com>; Ni, Ray <ray.ni@intel.com>;
> > > > Kumar, Chandana C <chandana.c.kumar@intel.com>; Zeng, Star
> > > > <star.zeng@intel.com>
> > > > Subject: RE: [edk2-devel] [PATCH] UefiCpuPkg CpuCommonFeaturesLib:
> > > > Remove CPU generation check
> > > >
> > > > Laszlo,
> > > >
> > > > > -----Original Message-----
> > > > > From: devel@edk2.groups.io [mailto:devel@edk2.groups.io] On
> > > > > Behalf Of Laszlo Ersek
> > > > > Sent: Thursday, May 16, 2019 9:06 PM
> > > > > To: Zeng, Star <star.zeng@intel.com>; devel@edk2.groups.io
> > > > > Cc: Dong, Eric <eric.dong@intel.com>; Ni, Ray
> > > > > <ray.ni@intel.com>; Kumar, Chandana C
> > > > > <chandana.c.kumar@intel.com>
> > > > > Subject: Re: [edk2-devel] [PATCH] UefiCpuPkg
> CpuCommonFeaturesLib:
> > > > > Remove CPU generation check
> > > > >
> > > > > Hi Star,
> > > > >
> > > > > On 05/16/19 12:33, Star Zeng wrote:
> > > > > > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1679
> > > > > >
> > > > > > The checking to CpuInfo->CpuIdVersionInfoEcx.Bits.AESNI is
> > > > > > enough, the checking to CPU generation could be removed, then
> > > > > > the code could be reused by more platforms.
> > > > > >
> > > > > > Cc: Laszlo Ersek <lersek@redhat.com>
> > > > > > Cc: Eric Dong <eric.dong@intel.com>
> > > > > > Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> > > > > > Cc: Chandana Kumar <chandana.c.kumar@intel.com>
> > > > > > Signed-off-by: Star Zeng <star.zeng@intel.com>
> > > > > > ---
> > > > > >  UefiCpuPkg/Library/CpuCommonFeaturesLib/Aesni.c | 12
> > > > > > +++---------
> > > > > >  1 file changed, 3 insertions(+), 9 deletions(-)
> > > > > >
> > > > > > diff --git a/UefiCpuPkg/Library/CpuCommonFeaturesLib/Aesni.c
> > > > > > b/UefiCpuPkg/Library/CpuCommonFeaturesLib/Aesni.c
> > > > > > index b79446ba3ca9..4a56eec1b267 100644
> > > > > > --- a/UefiCpuPkg/Library/CpuCommonFeaturesLib/Aesni.c
> > > > > > +++ b/UefiCpuPkg/Library/CpuCommonFeaturesLib/Aesni.c
> > > > > > @@ -57,15 +57,9 @@ AesniSupport (
> > > > > >    MSR_SANDY_BRIDGE_FEATURE_CONFIG_REGISTER
> > > > *MsrFeatureConfig;
> > > > > >
> > > > > >    if (CpuInfo->CpuIdVersionInfoEcx.Bits.AESNI == 1) {
> > > > > > -    if (IS_SANDY_BRIDGE_PROCESSOR (CpuInfo->DisplayFamily,
> > > CpuInfo-
> > > > > >DisplayModel) ||
> > > > > > -        IS_SILVERMONT_PROCESSOR (CpuInfo->DisplayFamily,
> CpuInfo-
> > > > > >DisplayModel) ||
> > > > > > -        IS_XEON_5600_PROCESSOR (CpuInfo->DisplayFamily, CpuInfo-
> > > > > >DisplayModel) ||
> > > > > > -        IS_XEON_E7_PROCESSOR (CpuInfo->DisplayFamily, CpuInfo-
> > > > > >DisplayModel) ||
> > > > > > -        IS_XEON_PHI_PROCESSOR (CpuInfo->DisplayFamily, CpuInfo-
> > > > > >DisplayModel)) {
> > > > > > -      MsrFeatureConfig =
> > > > > (MSR_SANDY_BRIDGE_FEATURE_CONFIG_REGISTER *) ConfigData;
> > > > > > -      ASSERT (MsrFeatureConfig != NULL);
> > > > > > -      MsrFeatureConfig[ProcessorNumber].Uint64 = AsmReadMsr64
> > > > > (MSR_SANDY_BRIDGE_FEATURE_CONFIG);
> > > > > > -    }
> > > > > > +    MsrFeatureConfig =
> > > > > (MSR_SANDY_BRIDGE_FEATURE_CONFIG_REGISTER *) ConfigData;
> > > > > > +    ASSERT (MsrFeatureConfig != NULL);
> > > > > > +    MsrFeatureConfig[ProcessorNumber].Uint64 = AsmReadMsr64
> > > > > > + (MSR_SANDY_BRIDGE_FEATURE_CONFIG);
> > > > > >      return TRUE;
> > > > > >    }
> > > > > >    return FALSE;
> > > > > >
> > > > >
> > > > > the patch and the bugzilla ticket claim that the AESNI bit's
> > > > > presence in CPUID guarantees that MSR 0x13C is available.
> > > >
> > > > That is the case we met. The purpose of this patch is to make the
> > > > code more usable.
> > > >
> > > > >
> > > > > I don't see what guarantees this. According to the latest Intel
> > > > > SDM Vol 4, which I just downloaded (335592-069US, January 2019),
> > > > > MSR_FEATURE_CONFIG is available on the following (DisplayFamily,
> > > > > DisplayModel) pairs:
> > > > >
> > > > > - 06_37H, 06_4AH, 06_4DH, 06_5AH, 06_5DH, 06_5CH, 06_7AH
> > > > > - 06_25H, 06_2CH
> > > > > - 06_2FH
> > > > > - 06_2AH, 06_2DH
> > > > > - 06_57H
> > > >
> > > > Yes, right.
> > > >
> > > > Let me show some examples for the generations not in the list above.
> > > >
> > > > 1. MSR 0x13C is available: our some internal generations are in this case.
> > > > Without the patch, code needs to use function level override
> > > > method in a CpuSpecificFeaturesLib.
> > > >     Status = RegisterCpuFeature (
> > > >                "AESNI",
> > > >                NULL,                                         // Use core function
> > > >                SpecificAesniSupport,                         // Override core function
> > > >                NULL,                                         // Use core function
> > > >                CPU_FEATURE_AESNI,
> > > >                CPU_FEATURE_END
> > > >                );
> > > > With the patch, the function level override will be not needed.
> > > > The benefit of this patch is here.
> > > >
> > > > 2. MSR 0x13C is not available: let's assume some other MSR will be
> > > > available for the case.
> > > > Without or with the patch, codes both need to use function level
> > > > override method in a CpuSpecificFeaturesLib.
> > > >     Status = RegisterCpuFeature (
> > > >                "AESNI",
> > > >                NULL,                                         // Use core function
> > > >                SpecificAesniSupport,                         // Override core function
> > > >                SpecificAesniInitialize,                         // Override core function
> > > >                CPU_FEATURE_AESNI,
> > > >                CPU_FEATURE_END
> > > >                );
> > > >
> > > >
> > > > Thanks,
> > > > Star
> > > >
> > > > >
> > > > > Which seems to indicate that at least *the approach* of the
> > > > > original code -- i.e. the family/model checking -- is correct.
> > > > > (It's possible that the family/model list has to be extended
> > > > > from time to time, of
> > > > > course.)
> > > > >
> > > > > Anyway, I don't intend to block this patch; OVMF does not use
> > > > > CpuCommonFeaturesLib, so this change cannot regress it. I will
> > > > > let other UefiCpuPkg reviewers decide about this patch.
> > > > >
> > > > > Thanks!
> > > > > Laszlo
> > > > >
> > > > >