Load qubes-hcl-report asynchronously and cache it per boot

[andreasglashauser]

For: QubesOS/qubes-issues#11081

Constructing the This Device page ran qubes-hcl-report -y synchronously on the main thread. That script shells out to sudo lspci -nnvk, sudo dmidecode, xl info and xl dmesg, so the UI was blocked for its duration on every visit to the page.

The report now runs in a background thread, showing placeholder text while it loads, and its output is cached.

The cache is keyed on /proc/sys/kernel/random/boot_id, so it is discarded after a reboot and reused within one. Every field the report contains is fixed for the lifetime of a boot: hardware identity from dmidecode and lspci, the BIOS version, since a firmware flash takes effect only after a reboot, the virtualization fields parsed out of the xl dmesg boot log, since changing VT-d in firmware likewise needs a reboot, and the running kernel and Xen versions. A time-based expiry would re-run the probe when nothing can have changed, and could still miss a change after a reboot inside the window.

Two cases are deliberately not cached: a failed run, and a report degraded by an incomplete xl dmesg ring buffer, which empties slat and the other virtualization fields. Caching either would make it stick for the rest of the boot. A Refresh button re-runs the report and bypasses the cache, which also covers the one field that can change within a boot, the release string in
/etc/qubes-release.

New tests in qubes_config/tests/test_thisdevice.py cover loading, a cache hit, invalidation on a changed boot id, both non-caching cases, and refresh. Since those tests stub out the worker thread and GLib.idle_add, I also
exercised the real threaded path by running the GUI against qubesadmin.tests.mock_app and confirming it wrote the cache.

Lazy page construction, the other half of #11081, is a separate PR against this repo. The two touch disjoint files and can be merged in either order.

AI disclosure: I did write every code on my own, but I used LLMs for getting reviews & feedback, as well as generating this ticket description from the diff via my own tool running local models.

[marmarek]

What do you think about doing the caching in the qubes-hcl-report script itself (at least if the yaml-only output is selected)?

[andreasglashauser]

What do you think about doing the caching in the qubes-hcl-report script itself (at least if the yaml-only output is selected)?

Yeah thats definitely the better way to fix this. I was already working on the Qubes Global Config for another PR and searched for ways to make it more efficient, which is why I implemented this way.
I will update this PR and open up a new one for doing the caching in qubes-hcl-report itself probably tomorrow.

[andreasglashauser]

Updated this PR: the caching is gone, so all it does now is move the report collection off the main thread and show placeholder text while it runs.

I also dropped the Refresh button that was in the earlier version, it only existed to bypass the cache that used to be here.

Caching in the script: QubesOS/qubes-core-admin#877

[marmarta]

some formatting complaints from linters, but otherwise this looks good to me. Good idea, btw.

[marmarta]

I tested this version and it works perfectly. Could you squash the linter commit into the main commit?

[andreasglashauser]

I tested this version and it works perfectly. Could you squash the linter commit into the main commit?

Done.

[marmarek]

PipelineRetry

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.88%. Comparing base (d0e7102) to head (7477b70).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #332      +/-   ##
==========================================
+ Coverage   92.79%   92.88%   +0.08%     
==========================================
  Files          66       67       +1     
  Lines       13844    13910      +66     
==========================================
+ Hits        12847    12920      +73     
+ Misses        997      990       -7     

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