Fix mmio interrupts

[bchalios]

Reason

According to the VirtIO spec section 2.1.2, when we enter a failed state we need to to set DEVICE_NEEDS_RESET status field and if DRIVER_OK is set we need to must send a device configuration change interrupt to the driver.

In MMIO code we were trying to follow this logic, but we were trying to get the interrupt object from the device, which fails (and panics) because interrupts are only set in the device upon successful activation. In the PCI transport, instead, we were not doing this at all.

Changes

For VirtIO devices, the transport layer always holds a reference to the interrupt object of the device. Use this reference in cases that we need to send an interrupt from the transport emulation logic. Moreover, add the missing logic in PCI transport to send a configuration update interrupt to the driver when we enter a failed state due to activation errors.

Also, there are places in VirtIO-MMIO code that takes and releases the virtio device lock multiple times within the same code branch. Change the logic to only do this once.

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

• I have read and understand CONTRIBUTING.md.
• I have run tools/devtool checkbuild --all to verify that the PR passes
  build checks on all supported architectures.
• 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.
• I have updated any relevant documentation (both in code and in the docs)
  in the PR.
• I have mentioned all user-facing changes in CHANGELOG.md.
• If a specific issue led to this PR, this PR closes the issue.
• When making API changes, I have followed the
  Runbook for Firecracker API changes.
• I have tested all new and changed functionalities in unit tests and/or
  integration tests.
• I have linked an issue to every new TODO.

---

• This functionality cannot be added in rust-vmm.

[codecov]

Codecov Report

❌ Patch coverage is 62.50000% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.64%. Comparing base (c9b0e64) to head (56830e5).
⚠️ Report is 2 commits behind head on feature/pcie.

Files with missing lines	Patch %	Lines
src/vmm/src/devices/virtio/transport/pci/device.rs	0.00%	8 Missing ⚠️
src/vmm/src/devices/virtio/transport/mmio.rs	93.75%	1 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           feature/pcie    #5351      +/-   ##
================================================
- Coverage         80.64%   80.64%   -0.01%     
================================================
  Files               265      265              
  Lines             30675    30674       -1     
================================================
- Hits              24738    24737       -1     
  Misses             5937     5937              

Flag	Coverage Δ
5.10-c5n.metal	80.43% <62.50%> (+<0.01%)	⬆️
5.10-m5n.metal	80.43% <62.50%> (-0.01%)	⬇️
5.10-m6a.metal	79.63% <62.50%> (-0.01%)	⬇️
5.10-m6g.metal	76.94% <62.50%> (-0.01%)	⬇️
5.10-m6i.metal	80.41% <62.50%> (-0.01%)	⬇️
5.10-m7a.metal-48xl	79.62% <62.50%> (-0.01%)	⬇️
5.10-m7g.metal	76.94% <62.50%> (-0.01%)	⬇️
5.10-m7i.metal-24xl	80.39% <62.50%> (-0.01%)	⬇️
5.10-m7i.metal-48xl	80.39% <62.50%> (-0.01%)	⬇️
5.10-m8g.metal-24xl	76.94% <62.50%> (-0.01%)	⬇️
5.10-m8g.metal-48xl	76.94% <62.50%> (-0.01%)	⬇️
6.1-c5n.metal	80.47% <62.50%> (-0.01%)	⬇️
6.1-m5n.metal	80.47% <62.50%> (-0.01%)	⬇️
6.1-m6a.metal	79.68% <62.50%> (-0.01%)	⬇️
6.1-m6g.metal	76.94% <62.50%> (-0.01%)	⬇️
6.1-m6i.metal	80.46% <62.50%> (-0.01%)	⬇️
6.1-m7a.metal-48xl	79.67% <62.50%> (-0.01%)	⬇️
6.1-m7g.metal	76.94% <62.50%> (-0.01%)	⬇️
6.1-m7i.metal-24xl	80.47% <62.50%> (-0.02%)	⬇️
6.1-m7i.metal-48xl	80.48% <62.50%> (-0.01%)	⬇️
6.1-m8g.metal-24xl	76.94% <62.50%> (-0.01%)	⬇️
6.1-m8g.metal-48xl	76.94% <62.50%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.