#4534: Remove multi irq support for mmio devices

[andr3wy]

Changes

-Utilized Option instead of Vector to store IRQ lines for MMIO devices. -Add test to test this. -Update existing tests ...

Reason

Currently, Firecracker have an ability to create multiple irqs for MMIO devices; however, no more than one IRQ is ever used. Therefore, it was suggested to change this to use an Option instead of a vector of length 0 or 1. ...

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[bot]]

Codecov Report

Attention: Patch coverage is 91.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 84.31%. Comparing base (3acf37d) to head (65e0e84). Report is 2 commits behind head on main.

:exclamation: Current head 65e0e84 differs from pull request most recent head a61d5c1

Please upload reports for the commit a61d5c1 to get more accurate results.

Files with missing lines	Patch %	Lines
src/vmm/src/device_manager/mmio.rs	91.66%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4601      +/-   ##
==========================================
- Coverage   84.32%   84.31%   -0.01%     
==========================================
  Files         249      249              
  Lines       27512    27516       +4     
==========================================
+ Hits        23200    23201       +1     
- Misses       4312     4315       +3     

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[andr3wy]

Issues should be resolved.

[roypat]

Thanks for squashing the commits! It seems that a rebase went a bit awry though, your branch now has some commits that are already on main :( Could you drop those, so that only your commit remains part of this PR? Also, please add a commit body message - it's required for the style CI step to pass - just rephrasing the what you put under "Reason" in the PR description will be fine :).

Also I think there's still a compilation issue on ARM, could you have a look at that, too?

[andr3wy]

Wanted to write that I won't have access to a computer for at least a month (out of town), so this will have to be on the back burner for a while.

[JonathanWoollett-Light]

Related to https://github.com/firecracker-microvm/firecracker/issues/4534

[roypat]

Wanted to write that I won't have access to a computer for at least a month (out of town), so this will have to be on the back burner for a while.

Hi @andr3wy, are you still interested in working on this?

[roypat]

Hi @andr3wy, I've gone ahead and rebased the PR, and fixed the remaining outstanding compiler warnings. Thanks again for your contribution here!