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References: <cover.1628767741.git.min.m.xu@intel.com> <31e974a9ef1ef191a1f76e81fa91047d12ee2169.1628767741.git.min.m.xu@intel.com>
In-Reply-To: <31e974a9ef1ef191a1f76e81fa91047d12ee2169.1628767741.git.min.m.xu@intel.com>
From: "Erdem Aktas" <erdemaktas@google.com>
Date: Sat, 11 Sep 2021 04:14:07 +0300
Message-ID: <CAAYXXYwTqLYGGd=iqk6RPNfJqzwChnz03WcGkb-xoKR=cCfkJg@mail.gmail.com>
Subject: Re: [PATCH 03/23] OvmfPkg/ResetVector: Enable Intel TDX in ResetVector of Ovmf
To: Min Xu <min.m.xu@intel.com>
Cc: edk2-devel-groups-io <devel@edk2.groups.io>, Ard Biesheuvel <ardb+tianocore@kernel.org>, 
	Jordan Justen <jordan.l.justen@intel.com>, Brijesh Singh <brijesh.singh@amd.com>, 
	James Bottomley <jejb@linux.ibm.com>, Jiewen Yao <jiewen.yao@intel.com>, 
	Tom Lendacky <thomas.lendacky@amd.com>
Content-Type: text/plain; charset="UTF-8"

On Thu, Aug 12, 2021 at 2:57 PM Min Xu <min.m.xu@intel.com> wrote:
>
> +;
> +; Check if it is Intel Tdx
> +;
> +; Modified: EAX, EBX, ECX, EDX
> +;
> +; If it is Intel Tdx, EAX is zero
> +; If it is not Intel Tdx, EAX is non-zero
> +;
> +IsTdx:
IsTdx returns 0 when TDX is enabled in CPUID but IsTdxEnabled return 1
when TDX is enabled. Is this intentional?

here is how IsTdxEnabled defined.
; If TDX is enabled then EAX will be 1
; If TDX is disabled then EAX will be 0.
;
IsTdxEnabled:

> +TdxApWait:
> +    cmp     byte[TDX_WORK_AREA_PGTBL_READY], 0
> +    je      TdxApWait
Don't we need memory fence before  je      TdxApWait. I did not check
what the compiler generates for this loop.


-Erdem