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Subject: Re: [PATCH 1/1] UefiCpuPkg/MpInitLib: Reduce reset vector memory pressure
From: "Laszlo Ersek" <lersek@redhat.com>
To: Tom Lendacky <thomas.lendacky@amd.com>, devel@edk2.groups.io
Cc: Eric Dong <eric.dong@intel.com>, Ray Ni <ray.ni@intel.com>,
 Rahul Kumar <rahul1.kumar@intel.com>, Brijesh Singh <brijesh.singh@amd.com>,
 Garrett Kirkendall <garrett.kirkendall@amd.com>
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Date: Wed, 23 Sep 2020 10:31:10 +0200
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On 09/23/20 10:14, Laszlo Ersek wrote:

> (3) Even better... can you modify GetApResetVectorSize() to take
> &CpuMpData rather than &CpuMpData->AddressMap, and then check
> CpuMpData->SevEsIsEnabled?
> 
> Hmmm, wait, that's not really simple, as we call GetApResetVectorSize()
> from MpInitLibInitialize() too, way before we set
> CpuMpData->SevEsIsEnabled from the PCD.
> 
> So I guess we should pass a dedicated BOOLEAN parameter to
> GetApResetVectorSize(), called "SevEsIsEnabled". At the call site in
> MpInitLibInitialize(), we should pass in the PCD's value. At the call
> site in AllocateResetVector(), we should pass in
> CpuMpData->SevEsIsEnabled.
> 
> The reason I'm suggesting (3) is that I don't feel comfortable with
> checking dynamic PCDs outside of entry point functions / initialization
> functions.

You know what, never mind (3) -- I've just realized that
PcdCpuMaxLogicalProcessorNumber may be a dynamic PCD too. It might
require a lot of work to restrict all dynamic PCD accesses to the init
function only, and I couldn't necessarily justify all that work at the
moment (for myself or for anyone else).

So please consider (1), (2) and (4).

Thanks!
Laszlo