Add TD Info as Initialization Header

[yuehtingchen]

TDX VMs require additional launch time configurations for better flexibility

• Adds td_info as an optional header in the IGVM file to store TDX specific configurations
• Add xfam as a parameter in td_info to specify extended processor feature enablement
• Validate td_info compatibility mask specifies TDX platform

[chris-oo]

Is this really optional if it impacts the measurement of the guest? It's optional in the sense of "if you don't specify this, the VMM may choose whatever value it likes" correct?

[yuehtingchen]

Yes. It's optional in the sense that the IGVM file should load even if you don't specify these fields. I don't think all guests care if the measurements are different across different hosts, so some guests may choose not to specify these fields.

[chris-oo]

But whatever the host has chosen to put for this value, will be reflected in the measurement report right?

[yuehtingchen]

Yes that's correct

[luigix25]

Hi @yuehtingchen, I have a few comments, just from the git POV, I'm not an IGVM expert so I'll leave that to the maintainers.

• I see that in this PR you add and revert the same commit, I suggest you to rebase so they cancel each other out.
• In commit fix compile errs you introduce a problem in dump_igvm.c that you fix in fix c build errs. Why not squashing them together?
• Same goes for format fixes: why introduce a "problem" and then fix it later? You can do it in one shot.
• Try to write commit messages that explain why you are doing something. https://www.kernel.org/doc/html/v4.10/process/submitting-patches.html#describe-your-changes I hope this guide helps you.

Thanks!

[chris-oo]

Note that we do squash PRs for this repo, but the feedback is still useful as it helps reviewers logically reason about changes.