Cleaning up create_fdt

[jackabald]

Changes

Adds fdt to guest memory at the location create_fdt is called not in create_fdt.
Removes unnecessary std::hash::BuildHasher parameterization.
...

Reason

@roypat we are not able to remove the GuestMemoryMmap parameter because we use it to create the memory node.
However, this updated code now writes the fdt to guest memory at the site of the caller utilizing the previously unused return value from create_fdt.

• separation of concerns
• simplify unit testing
  Clean up create_fdt function in src/vmm/src/arch/aarch64/fdt.rs #4700

...

License Acceptance

By submitting this pull request, I confirm that my contribution is made under
the terms of the Apache 2.0 license. For more information on following Developer
Certificate of Origin and signing off your commits, please check
CONTRIBUTING.md.

PR Checklist

• If a specific issue led to this PR, this PR closes the issue.
• The description of changes is clear and encompassing.
• Any required documentation changes (code and docs) are included in this
  PR.
• API changes follow the Runbook for Firecracker API changes.
• User-facing changes are mentioned in CHANGELOG.md.
• All added/changed functionality is tested.
• New TODOs link to an issue.
• Commits meet
  contribution quality standards.

---

• This functionality cannot be added in rust-vmm.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.38%. Comparing base (6d2bf72) to head (77eabb9).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4712   +/-   ##
=======================================
  Coverage   84.38%   84.38%           
=======================================
  Files         249      249           
  Lines       27494    27496    +2     
=======================================
+ Hits        23201    23203    +2     
  Misses       4293     4293           

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[roypat]

we are not able to remove the GuestMemoryMmap parameter because we use it to create the memory node.

ah, rip, I missed that. Oh well, this is still an improvement :D Could you have a look at fixing the compilation errors/warnings, though? :o

[roypat]

Hi @jackabald,
did you have a chance to look at this again yet?

[ShadowCurse]

Hi @jackabald, are you still working on this?

[jackabald]

hey @ShadowCurse , sorry haven't looked at this in a bit. I am having troubles finding why the build is failing. If you could take a look that would be great!

[ShadowCurse]

So the issue is in the absence of GuestAddress import in the src/vmm/src/arch/aarch64/fdt.rs. Basically you need to drop last commit that reverts addition of this import.
Also can you please rebase this PR on top of main and squash rest of your commits?

[roypat]

Hi @jackabald,
I've gone ahead and fixed the small import issue, so we can go ahead with merging this. Thanks again for your contribution!