[edk2-devel] [PATCH V2 14/28] OvmfPkg: Update SecEntry.nasm to support Tdx

[Min Xu]

On October 12, 2021 6:39 PM, Gerd Hoffmann wrote:
>   Hi,
> 
> >  - AcceptPages:
> >    To mitigate the performance impact of accepting pages in SEC phase on
> >    BSP, BSP will parse memory resources and assign each AP the task of
> >    accepting a subset of pages. This command may be called several times
> >    until all memory resources are processed. In accepting pages, PageLevel
> >    may fall back to smaller one if SIZE_MISMATCH error is returned.
> 
> Hmm, I'm wondering whenever it is useful to have this in the first place with
> the longer-term plan to implement lazy on-demand acceptance.
To mitigate the performance impact of accepting pages, there are 3 ways.
1. Big accept page size.
2. Accept the pages by BSP and APs together.
3. Lazy on-demand acceptance.
>From the perspective of implementation complexity, 1 < 2 < 3.
Lazy on-demand acceptance need the update not only in TDVF, but also in Guest kernel. More investigation shows it also impacts the grub and memory management in EDK2.
>From the perspective of performance improvement, 2M accept page size + BSP/AP together, can improve the performance a lot. 
Based on above consideration, in current TDVF upstream, 1 + 2 are the ways to mitigate the performance impact.
Upstream of 3 is in the future plan.

Thanks!
Min


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