vitual_network/../driver_packed: enable on s390x

[smitterl]

s390x uses virtio-ccw for all virtio downstream. Enable getting the feature attribute for those devices but don't change logic for existing tests which assume virtio-pci.

Summary by CodeRabbit

• Tests
  • Added support for validating packed virtqueue functionality across PCI and s390 (CCW) bus architectures.
  • Added a new test configuration for the s390-virtio bus type to broaden coverage.
  • Enhanced validation logic with bus-type-specific checks, improved error handling for unknown bus types, and a sensible default bus selection for existing tests.

[smitterl]

JOB ID     : a1a24312b006f1d87a00838bc701298a359480a0
JOB LOG    : /var/log/avocado/job-results/job-2026-02-05T07.41-a1a2431/job.log
 (1/1) type_specific.io-github-autotest-libvirt.virtual_network.elements_and_attributes.driver_packed: STARTED
 (1/1) type_specific.io-github-autotest-libvirt.virtual_network.elements_and_attributes.driver_packed:  PASS (29.69 s)
RESULTS    : PASS 1 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0 | CANCEL 0
JOB HTML   : /var/log/avocado/job-results/job-2026-02-05T07.41-a1a2431/results.html
JOB TIME   : 31.02 s

[coderabbitai]

Walkthrough

Added a new s390-virtio configuration block with bustype = ccw to driver_packed.cfg. In driver_packed.py the packed-virtqueue check gained a bustype parameter and dispatches to PCI or CCW verification paths. Implemented PCI-specific and CCW-specific checks, a helper to find subchannels by CU Type, a helper to read/validate virtio features files, import of SubchannelPaths, and expanded error handling for unknown bus types; default bustype remains pci.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Title check	⚠️ Warning	The title contains a typo ('vitual' instead of 'virtual') and uses a vague path reference ('../driver_packed') that obscures the actual change being made.	Correct the typo and clarify the title to something like 'Add s390x CCW support for packed virtqueue validation' to better reflect the main change.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

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

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[coderabbitai]

Actionable comments posted: 2

🤖 Fix all issues with AI agents

In `@libvirt/tests/src/virtual_network/elements_and_attributes/driver_packed.py`:
- Around line 58-70: The helper _check_features_file references an undefined
pci_addr causing a NameError; update _check_features_file to accept a pci_addr
parameter (e.g., def _check_features_file(virtio_features_file, session,
expected_packed_bit, test, pci_addr)) and update all callers (such as
_check_packed_virtqueue_ccw) to pass the VM PCI address through when calling
_check_features_file so the failure message can include the correct pci_addr and
avoid the NameError. Ensure the function signature and all invocations use the
new parameter name consistently.
- Around line 103-110: The current mapping from subchannel to virtio index in
the block using iface_cu_type, _get_subchannel_by_cu_type(...), and index =
subchannel.replace("0", "").replace(".", "") corrupts IDs; change it to extract
the device number component from the subchannel (e.g., take the last
dot-separated component of subchannel) and use that as index before building
virtio_features_file, or alternatively implement a lookup that scans
/sys/bus/virtio/devices/ for the device that links back to the subchannel to
obtain the actual virtio index; update the code around where index is computed
and keep the call to _check_features_file(virtio_features_file, session,
expected_packed_bit, test) unchanged.

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@libvirt/tests/src/virtual_network/elements_and_attributes/driver_packed.py`:
- Around line 59-70: The helper _check_features_file currently builds and runs a
shell command using virtio_features_file without validating it, so an empty/None
value will produce a confusing shell error; add a guard at the start of
_check_features_file that checks if virtio_features_file is truthy and a
non-empty string, and if not call test.error/test.fail (or test.log.error) with
a clear message that does NOT reference the undefined pci_addr, then
return/raise to avoid running the cat command; keep the rest of the function
(session, expected_packed_bit, test) unchanged.

🧹 Nitpick comments (1)

libvirt/tests/src/virtual_network/elements_and_attributes/driver_packed.py (1)

53-56: Missing validation for find command output.

If the find command returns empty output (no matching features file), or multiple lines (multiple matches), this value is passed directly to _check_features_file where cat would fail with a confusing error message.

Consider validating the output:

♻️ Proposed validation

     find_cmd = 'find / -name features | grep "%s"' % pci_addr
     virtio_features_file = session.cmd_output(find_cmd)
+    virtio_features_file = virtio_features_file.strip()
+    if not virtio_features_file:
+        test.fail(f"Virtio features file not found for PCI address {pci_addr}")
 
     _check_features_file(virtio_features_file, session, expected_packed_bit, test)

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Input validation was removed instead of fixed.

The past review flagged an undefined pci_addr in the error message. The fix removed the entire validation check rather than simplifying the message. Now if virtio_features_file is empty or None, line 70's cat command will fail with a confusing error.

🛡️ Proposed fix to add validation

 def _check_features_file(virtio_features_file, session, expected_packed_bit,  test):
     """
     Check packed information from features file
 
     :param virtio_features_file: the features attribute of the virtio device
     :param session: VM session
     :param expected_packed_bit: Expected packed bit value
     :param test: test instance
     """
+    if not virtio_features_file or not virtio_features_file.strip():
+        test.fail("Virtio features file not found")
     test.log.debug(f"Using virtio features file: {virtio_features_file}")
 
     packed_bit_cmd = f"cat {virtio_features_file}"

🤖 Prompt for AI Agents

In `@libvirt/tests/src/virtual_network/elements_and_attributes/driver_packed.py`
around lines 59 - 70, The helper _check_features_file currently builds and runs
a shell command using virtio_features_file without validating it, so an
empty/None value will produce a confusing shell error; add a guard at the start
of _check_features_file that checks if virtio_features_file is truthy and a
non-empty string, and if not call test.error/test.fail (or test.log.error) with
a clear message that does NOT reference the undefined pci_addr, then
return/raise to avoid running the cat command; keep the rest of the function
(session, expected_packed_bit, test) unchanged.