fix: rename page_size_kib to page_size

[acsmyth]

Changes

• update page_size_kib name to the more accurate page_size, since it's actually in bytes, not KiB.
  ...

Reason

Minor API break with the uffd socket, but since it's relatively new, deleting the incorrectly-named field outright seems better than deprecating it / leaving it around.

...

License Acceptance

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PR Checklist

• I have read and understand CONTRIBUTING.md.
• I have run tools/devtool checkstyle to verify that the PR passes the
  automated style checks.
• I have described what is done in these changes, why they are needed, and
  how they are solving the problem in a clear and encompassing way.
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  in the PR.
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• If a specific issue led to this PR, this PR closes the issue.
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---

• This functionality cannot be added in rust-vmm.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.07%. Comparing base (1f94a59) to head (b7355b4).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4948   +/-   ##
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  Coverage   84.07%   84.07%           
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  Files         251      251           
  Lines       28059    28059           
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  Hits        23592    23592           
  Misses       4467     4467           

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[pb8o]

Is this intended? the smaps file does report this value in kB:

KernelPageSize:        4 kB

I think this should be left as-is.

[pb8o]

Other than that, it looks good to me. Thanks for your contribution! :)

[roypat]

Hi @acsmyth,
thanks for catching this! The team's discussed this, and we agreed that although huge pages support is somewhat new, this would still be a breaking change, and so there should be some sort of transition period for users of Firecracker. So for that reason, I think we should just carry two fields for a while (e.g. both page_size and page_size_kib with the broken semantics). That being said, I think most of your PR can go through unchanged, we'll only need to readd page_size_kib to GuestRegionUffdMapping and set it to the same value as page_size in create_guest_memory. We'd also need to add something to DEPRECATED.md warning that we'll remove page_size_kib in an upcoming version.