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Date: Fri, 26 Aug 2022 11:11:44 +0200
From: "Gerd Hoffmann" <kraxel@redhat.com>
To: "Xu, Min M" <min.m.xu@intel.com>
Cc: "devel@edk2.groups.io" <devel@edk2.groups.io>,
	"Aktas, Erdem" <erdemaktas@google.com>,
	James Bottomley <jejb@linux.ibm.com>,
	"Yao, Jiewen" <jiewen.yao@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [edk2-devel] [PATCH V3 2/2] OvmfPkg: Update CcProbeLib to DxeCcProbeLib
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On Fri, Aug 26, 2022 at 08:21:49AM +0000, Xu, Min M wrote:
> On August 26, 2022 1:23 PM, Gerd Hoffmann wrote:
> >   Hi,
> > 
> > > In DxeCcProbeLib we cache the GuestType in Ovmf work area in first-call.
> > > After that the Guest type is returned with the cached value. So that
> > > we don't need to worry about the access to Ovmf work area after
> > > ExitBootService.
> > 
> > This only works in case the first call is early enough.
> > Better use a CONSTRUCTOR instead.
> > 
> Thanks for reminder.
> There is another situation that the first call of DxeCcProbeLib is earlier than its CONSTRUCTOR.
> For example, in MdeModulePkg/Core/Dxe/DxeMain, BaseDebugLibSerialPortConstructor is called before DxeCcProbeLibConstructor. While CcProbe () is called in BaseDebugLibSerialPortConstructor.
> So I would like to read the Cc guest type in both CONSTRUCTOR and CcProbe.

Makes sense (and please add a comment explaining this corner case).

take care,
  Gerd