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Date: Tue, 12 Oct 2021 12:15:57 +0200
From: "Gerd Hoffmann" <kraxel@redhat.com>
To: devel@edk2.groups.io, min.m.xu@intel.com
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>,
	Erdem Aktas <erdemaktas@google.com>,
	James Bottomley <jejb@linux.ibm.com>,
	Jiewen Yao <jiewen.yao@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [edk2-devel] [PATCH V2 07/28] UefiCpuPkg: Support TDX in BaseXApicX2ApicLib
Message-ID: <20211012101557.j5xjtrlyofj3tadb@sirius.home.kraxel.org>
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  Hi,

> +  do {
> +    AsmCpuid (0, &LargestEax, &Ebx, &Ecx, &Edx);

Use ConfidentialComputing PCD ?

> +BOOLEAN
> +EFIAPI
> +AccessMsrNative (

I'd suggest to reverse the logic, i.e. have a AccessMsrTdxCall() which
returns true in case (a) tdx is active and (b) the msr is not on the
white list for native access ...

> +{
> +  UINT64    Val;
> +  UINT64    Status;
> +  if (!AccessMsrNative (MsrIndex) && BaseXApicIsTdxGuest ()) {

... the just use "if (AccessMsrTdxCall(MsrIndex)) { ..." here.

Beside that:  Are the apic msr registers the only ones which can
be accessed directly?

take care,
  Gerd