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Subject: Re: [edk2-devel] [Patch] MdeModulePkg DxeCore: Fix for missing MAT update
To: "Gao, Liming" <liming.gao@intel.com>,
 "Kinney, Michael D" <michael.d.kinney@intel.com>,
 "devel@edk2.groups.io" <devel@edk2.groups.io>
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>
From: "Laszlo Ersek" <lersek@redhat.com>
Message-ID: <28d0e7fa-35c8-ca4b-a476-3afdd5d1c3a2@redhat.com>
Date: Wed, 14 Aug 2019 17:12:41 +0200
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On 08/14/19 16:00, Gao, Liming wrote:
> Laszlo:

> 
> I cherry pick this patch from Mu project with the minimal change. 
> I can update the comment style. 

Yes, please. Thanks!

>> The gEfiMemoryTypeInformationGuid HOB is supposed to be built -- if it
>> is built at all -- no later than in the DXE IPL PEIM (if VariablePei is
>> included in the platform, and the underlying UEFI variable exists). Is
>> that correct?
>>
> gEfiMemoryTypeInformationGuid HOB is installed by platform PEI. 

Yes, that's what I meant by "no later than in the DXE IPL PEIM".

> If the platform PEI doesn't install this HOB, it means this feature is disabled. 

PlatformPei is supposed to build the HOB in the first place, yes.

However, if it doesn't, then there still may be a feedback loop between
the DXE IPL PEIM and BDS. The former builds the HOB from the UEFI
variable, and the latter updates the variable (as I understand) for
future boots.

Thanks
Laszlo