Re: [edk2-rfc] [edk2-devel] RFC: design review for TDVF in OVMF

["Min Xu" <min.m.xu@intel.com>]

On June 6, 2021 7:30 PM, Michael Brown Wrote:
> 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.
> 

In our first version of TDVF, a static 5-level page table is used. It is simple and
straight forward. But for *one binary* solution, we have to consider the compatibility
with the current 4-level page table. That's why I said "I would wait for the conclusion
of the *one binary*"

Thanks for the suggestion. We will discuss the it internally first.

> Michael