Re: [PATCH] UefiCpuPkg/MpInitLib: Skip reading PlatformId on AMD processors.

["Ni, Ray" <ray.ni@intel.com>]

Did you try the build?
I saw "error C2065: CPUID_SIGNATURE_AUTHENTIC_AMD_EBX: undeclared identifier" in my internal build report with this patch.

Thanks,
Ray

> -----Original Message-----
> From: Laszlo Ersek <lersek@redhat.com>
> Sent: Saturday, February 29, 2020 3:33 PM
> To: Leo Duran <leo.duran@amd.com>; devel@edk2.groups.io
> Cc: Dong, Eric <eric.dong@intel.com>; Ni, Ray <ray.ni@intel.com>
> Subject: Re: [PATCH] UefiCpuPkg/MpInitLib: Skip reading PlatformId on AMD processors.
> 
> On 02/28/20 19:58, Leo Duran wrote:
> > REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2556
> >
> > This patch uses CPUID signature check to skip reading the PlatformId MSR,
> > which is not implemented on AMD processors.
> >
> > The PlatformId is used for loading microcode patches, which is also not
> > supported and AMD-based platforms. To mitigate the PlatformId dependency,
> > PcdCpuMicrocodePatchAddress and PcdCpuMicrodePatchRegionSize must be set
> > to 0 (default value), in order to bypass microcode loading code paths.
> >
> > Cc: Eric Dong <eric.dong@intel.com>
> > Cc: Ray Ni <ray.ni@intel.com>
> > Cc: Laszlo Ersek <lersek@redhat.com>
> > Signed-off-by: Leo Duran <leo.duran@amd.com>
> > ---
> >  UefiCpuPkg/Library/MpInitLib/MpLib.c | 34 ++++++++++++++++++++++++++++++++--
> >  1 file changed, 32 insertions(+), 2 deletions(-)
> >
> > diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> > index d0fbc17..d2200c3 100644
> > --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
> > +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> > @@ -2,6 +2,8 @@
> >    CPU MP Initialize Library common functions.
> >
> >    Copyright (c) 2016 - 2020, Intel Corporation. All rights reserved.<BR>
> > +  Copyright (c) 2020, AMD Inc. All rights reserved.<BR>
> > +
> >    SPDX-License-Identifier: BSD-2-Clause-Patent
> >
> >  **/
> > @@ -10,6 +12,29 @@
> >
> >  EFI_GUID mCpuInitMpLibHobGuid = CPU_INIT_MP_LIB_HOB_GUID;
> >
> > +
> > +/**
> > +  Determine if the standard CPU signature is "AuthenticAMD".
> > +
> > +  @retval TRUE  The CPU signature matches.
> > +  @retval FALSE The CPU signature does not match.
> > +
> > +**/
> > +BOOLEAN
> > +StandardSignatureIsAuthenticAMD (
> > +  VOID
> > +  )
> > +{
> > +  UINT32  RegEbx;
> > +  UINT32  RegEcx;
> > +  UINT32  RegEdx;
> > +
> > +  AsmCpuid (CPUID_SIGNATURE, NULL, &RegEbx, &RegEcx, &RegEdx);
> > +  return (RegEbx == CPUID_SIGNATURE_AUTHENTIC_AMD_EBX &&
> > +          RegEcx == CPUID_SIGNATURE_AUTHENTIC_AMD_ECX &&
> > +          RegEdx == CPUID_SIGNATURE_AUTHENTIC_AMD_EDX);
> > +}
> > +
> >  /**
> >    The function will check if BSP Execute Disable is enabled.
> >
> > @@ -564,8 +589,13 @@ InitializeApData (
> >    CpuMpData->CpuData[ProcessorNumber].Waiting    = FALSE;
> >    CpuMpData->CpuData[ProcessorNumber].CpuHealthy = (BistData == 0) ? TRUE : FALSE;
> >
> > -  PlatformIdMsr.Uint64 = AsmReadMsr64 (MSR_IA32_PLATFORM_ID);
> > -  CpuMpData->CpuData[ProcessorNumber].PlatformId = (UINT8) PlatformIdMsr.Bits.PlatformId;
> > +  //
> > +  // NOTE: PlatformId is not relevant on AMD platforms.
> > +  //
> > +  if (!StandardSignatureIsAuthenticAMD ()) {
> > +    PlatformIdMsr.Uint64 = AsmReadMsr64 (MSR_IA32_PLATFORM_ID);
> > +    CpuMpData->CpuData[ProcessorNumber].PlatformId = (UINT8)PlatformIdMsr.Bits.PlatformId;
> > +  }
> >
> >    AsmCpuid (
> >      CPUID_VERSION_INFO,
> >
> 
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>