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Subject: Re: [edk2-rfc] [edk2-devel] RFC: design review for TDVF in OVMF
To: devel@edk2.groups.io, min.m.xu@intel.com,
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From: "Michael Brown" <mcb30@ipxe.org>
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Date: Sun, 6 Jun 2021 12:29:40 +0100
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On 06/06/2021 03:03, Min Xu wrote:
>> (11) "Page table should support both 4-level and 5-level page 
>> table"
>> 
>> As a general development strategy, I would suggest building TDX 
>> support in small, well-isolated layers. 5-level paging is not 
>> enabled (has never been tested, to my knowledge) with OVMF on 
>> QEMU/KVM, regardless of confidential computing, for starters. If 
>> 5-level paging is a strict requirement for TDX, then it arguably 
>> needs to be implemented independently of TDX, at first. So that the
>> common edk2 architecture be at least testable on QEMU/KVM with 
>> 5-level paging enabled.
>> 
> Yes, 5-level paging is a strict requirement for TDX. I would wait for
> the conclusion of the *one binary*.

The "one binary" decision isn't relevant here, is it?  It would make
more sense to implement 5-level paging within the base EDK2
architecture.  This would allow that feature to be tested in isolation
from TDX (and consequently tested more widely), and would reduce the
distance between standard builds and TDX builds.

Michael