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Subject: Re: [edk2-devel] [Patch] MdeModulePkg DxeCore: Fix for missing MAT update
To: "Gao, Liming" <liming.gao@intel.com>,
 "devel@edk2.groups.io" <devel@edk2.groups.io>,
 "Kinney, Michael D" <michael.d.kinney@intel.com>
Cc: Mike Turner <miketur@microsoft.com>, "Wang, Jian J"
 <jian.j.wang@intel.com>, "Wu, Hao A" <hao.a.wu@intel.com>,
 "Bi, Dandan" <dandan.bi@intel.com>
References: <20190810141022.18228-1-liming.gao@intel.com>
 <66665886-fff1-248a-77e5-6b8fb6966f86@redhat.com>
 <E92EE9817A31E24EB0585FDF735412F5B9D87B11@ORSMSX113.amr.corp.intel.com>
 <96f6e8a3-7049-478a-a8f2-4389c06f0e12@redhat.com>
 <4A89E2EF3DFEDB4C8BFDE51014F606A14E4D0EE7@SHSMSX104.ccr.corp.intel.com>
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 <4A89E2EF3DFEDB4C8BFDE51014F606A14E4D101F@SHSMSX104.ccr.corp.intel.com>
From: "Laszlo Ersek" <lersek@redhat.com>
Message-ID: <684cdd50-88d7-500e-ca56-c59f11e0e615@redhat.com>
Date: Fri, 16 Aug 2019 17:18:27 +0200
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On 08/14/19 17:55, Gao, Liming wrote:

> If Platform PEIM doesn't build HOB, DxeIpl will not build HOB, 

My reading of the code is the opposite. If the platform PEIM does not build the HOB, then the DXE IPL PEIM will attempt to build the HOB, from the UEFI variable.

At commit caa7d3a896f6, in file "MdeModulePkg/Core/DxeIplPeim/DxeLoad.c", function DxeLoadCore(), we have:

   363    if (GetFirstGuidHob ((CONST EFI_GUID *)&gEfiMemoryTypeInformationGuid) == NULL) {
   364      //
   365      // Don't build GuidHob if GuidHob has been installed.
   366      //
   367      Status = PeiServicesLocatePpi (
   368                 &gEfiPeiReadOnlyVariable2PpiGuid,
   369                 0,
   370                 NULL,
   371                 (VOID **)&Variable
   372                 );
   373      if (!EFI_ERROR (Status)) {
   374        DataSize = sizeof (MemoryData);
   375        Status = Variable->GetVariable (
   376                             Variable,
   377                             EFI_MEMORY_TYPE_INFORMATION_VARIABLE_NAME,
   378                             &gEfiMemoryTypeInformationGuid,
   379                             NULL,
   380                             &DataSize,
   381                             &MemoryData
   382                             );
   383        if (!EFI_ERROR (Status) && ValidateMemoryTypeInfoVariable(MemoryData, DataSize)) {
   384          //
   385          // Build the GUID'd HOB for DXE
   386          //
   387          BuildGuidDataHob (
   388            &gEfiMemoryTypeInformationGuid,
   389            MemoryData,
   390            DataSize
   391            );
   392        }
   393      }
   394    }

Thanks
Laszlo