libvirt_mem : While doing hot unplug ,if detach-device error encountered

[sneh-3]

added retry attempt with systemctl restart qemu-guest-agent .

The following test cases were failing before ,

1. type_specific.io-github-autotest-libvirt.libvirt_mem.positive_test.memory.hot.unplug.max_slots.without_reboot
2. type_specific.io-github-autotest-libvirt.libvirt_mem.positive_test.memory.hot.unplug.max_slots.with_rand_reboot

Summary by CodeRabbit

• Tests
  • Enhanced memory detach operation testing with improved error detection and recovery procedures.
  • Added diagnostic capabilities for identifying and handling known unplug errors, including automatic service recovery and logging.

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[coderabbitai]

Walkthrough

This change introduces an enhanced retry mechanism in the memory detach process for handling known host unplug errors. When such errors are detected by scanning stderr output (including quoted entries), the code marks the failure, performs an additional detach attempt, and on continued failure, restarts the qemu-guest-agent service and retries. If detach still fails, diagnostic dmesg logs are collected and the VM connection is verified. The implementation adds conditional branches and exception handling around the new retry path.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20-25 minutes

• Stderr scanning logic: Review the string parsing and quoted entry handling for known error detection
• Retry mechanism conditions: Verify the logic flow across multiple retry attempts and state transitions
• Exception handling: Ensure proper exception catching and recovery paths are correctly implemented
• qemu-guest-agent restart: Confirm the service restart logic is appropriately placed and handles edge cases
• Diagnostic flow: Review the dmesg collection and VM verification logic for completeness

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly addresses the main change: enhanced retry mechanism for detach-device errors during memory hot-unplug with qemu-guest-agent restart.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between a302a6f and f91afe3.

📒 Files selected for processing (1)

• libvirt/tests/src/libvirt_mem.py (1 hunks)

🧰 Additional context used

🧬 Code graph analysis (1)

libvirt/tests/src/libvirt_mem.py (1)

libvirt/tests/src/controller/controller_functional.py (1)

• detach_device (563-576)

🪛 ast-grep (0.40.0)

libvirt/tests/src/libvirt_mem.py

[warning] 750-750: The function mktemp is deprecated. When using this function, it is possible for an attacker to modify the created file before the filename is returned. Use NamedTemporaryFile() instead and pass it the delete=False parameter.
Context: tempfile.mktemp(dir=data_dir.get_tmp_dir())
Note: [CWE-377]: Insecure Temporary File [OWASP A01:2021]: Broken Access Control [REFERENCES]
https://docs.python.org/3/library/tempfile.html#tempfile.mktemp
https://owasp.org/Top10/A01_2021-Broken_Access_Control

(avoid-mktemp-python)

🪛 Ruff (0.14.5)

libvirt/tests/src/libvirt_mem.py

735-735: Loop control variable retry_attempt not used within loop body

Rename unused retry_attempt to _retry_attempt

(B007)

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742-742: Do not catch blind exception: Exception

(BLE001)

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742-742: Local variable detail is assigned to but never used

Remove assignment to unused variable detail

(F841)

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745-745: Undefined name subprocess

(F821)

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750-750: Do not catch blind exception: Exception

(BLE001)

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750-750: Local variable detail2 is assigned to but never used

Remove assignment to unused variable detail2

(F841)

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751-751: Use of insecure and deprecated function (mktemp)

(S306)

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757-757: Do not catch blind exception: Exception

(BLE001)

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