Re: [edk2-devel] [PATCH] UefiCpuPkg/MpInitLib: Skip reading PlatformId on AMD processors.

["Gary Lin" <glin@suse.com>]

On Sat, Feb 29, 2020 at 09:05:45AM -0600, 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.
> 
I got an error report about the executable bit of MpLib.h while
packaging ovmf. It turned out that this patch accidentally changed the
file mode. It would be nice if the mode can be corrected.

Thanks,

Gary Lin

> 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 ++++++++++++++++++++++++++++++++--
>  UefiCpuPkg/Library/MpInitLib/MpLib.h |  3 +++
>  2 files changed, 35 insertions(+), 2 deletions(-)
>  mode change 100644 => 100755 UefiCpuPkg/Library/MpInitLib/MpLib.h
> 
> 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,
> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.h b/UefiCpuPkg/Library/MpInitLib/MpLib.h
> old mode 100644
> new mode 100755
           ^^^^^^
	   mode change
> index 455cb3f..0c89f8a
> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.h
> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.h
> @@ -2,6 +2,8 @@
>    Common header file for MP Initialize Library.
>  
>    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
>  
>  **/
> @@ -12,6 +14,7 @@
>  #include <PiPei.h>
>  
>  #include <Register/Intel/Cpuid.h>
> +#include <Register/Amd/Cpuid.h>
>  #include <Register/Intel/Msr.h>
>  #include <Register/Intel/LocalApic.h>
>  #include <Register/Intel/Microcode.h>
> -- 
> 2.7.4
> 
> 
> 
>