On 06/06/21 14:49, Xu, Min M wrote:
On June 6, 2021 7:30 PM, Michael Brown Wrote:My primary concern with the 5-level paging is not that the coreOn 06/06/2021 03:03, Min Xu wrote:In our first version of TDVF, a static 5-level page table is used. It is simple andThe "one binary" decision isn't relevant here, is it? It would make more(11) "Page table should support both 4-level and 5-level page table"Yes, 5-level paging is a strict requirement for TDX. I would wait for
infrastructure is absent from edk2 -- it is present alright. (Over time,
numerous issues have been found and fixed in it, but that's kind of
expected, with such a big feature.) I understand it has been in use
successfully on a number of physical platforms.
My problem is that, AFAICT, the 5-level paging infrastructure of edk2
has never been *tested* on QEMU/KVM, as a part of OVMF. I have
absolutely no idea what to expect.
The "one binary" decision is a little bit relevant:
- If 5-level paging blows up on QEMU/KVM, as a part of OVMF, then
restricting the breakage (possibly a regression even?) to the new TDX
platform is good.
- On the other hand, both 5-level paging and TDX are complex in their
own rights; developing feature sets in small isolated waves is always
best. There are going to be "bug hunts" in the TDX platform of course;
finding an *orthogonal* 5-level paging bug (anywhere in the virt stack,
for that matter) is not the greatest outcome for a supposed TDX bug hunt.
- I figure users might want 5-level paging for OVMF at some point
anyway, even without TDX.
The last two points (especially the middle point of the three) kind of
outweigh(s) the first point for me.