fix(monitor): clamp DeviceNum to maxDevices to prevent scrape-path panic

[Nakshatra480]

Summary

DeviceNum() in v0/spec.go and v1/spec.go returns int(s.sr.num) , an
unclamped raw read from the shared-memory region. collectContainerMetrics in
cmd/vGPUmonitor/metrics.go loops for i := range c.Info.DeviceNum() and
calls DeviceUUID(i) and DeviceMemoryLimit(i), which index into [16]uuid
and [16]uint64 arrays respectively. When sr.num exceeds 16 due to a
version mismatch or a partial libvgpu write, every Prometheus scrape causes an
index out of range panic that crashes vGPUmonitor and silences all GPU metrics
on that node.

• pkg/monitor/nvidia/v0/spec.go: DeviceNum() now returns min(int(s.sr.num), maxDevices)
• pkg/monitor/nvidia/v1/spec.go: same
• pkg/monitor/nvidia/v0/spec_test.go: added "num larger than maxDevices is clamped" to TestSpec_DeviceNum
• pkg/monitor/nvidia/v1/spec_test.go: added the same to Test_DeviceNum; also tightened existing table entries to inline form
• All tests pass: go test ./pkg/monitor/nvidia/... -count=1

This applies the same min(_, maxDevices) guard already used in activeProcs()
(via #2282) and the setter loops (via #2362) to the getter that drives the
scrape loop.

Which issue(s) this PR fixes:
Part of #2126 (LFX observability hardening - vGPU monitor stability)

Special notes for your reviewer:
DeviceUUID(i) and DeviceMemoryLimit(i) are called immediately after the
DeviceNum() loop bound, both access fixed-size [16] arrays so i >= 16
is an out-of-bounds panic, not a silent wrong value.

Does this PR introduce a user-facing change?
Yes vGPUmonitor no longer panics when sr.num exceeds 16; per-device GPU
metrics continue to be reported correctly.

Summary by CodeRabbit

• Bug Fixes

  • Corrected GPU device count reporting when the detected count exceeds the supported maximum.
  • Device counts are now safely limited to the maximum supported value, preventing invalid or unexpectedly large counts in monitoring results.
  • Applied consistently across supported NVIDIA monitoring versions.

• Tests

  • Added coverage to verify that excessive device counts are properly capped.

AI Disclosure:
AI assistance was used for code inspection and draft formatting.

[coderabbitai]

📝 Walkthrough

Walkthrough

Spec.DeviceNum now caps shared-region device counts at maxDevices in NVIDIA v0 and v1. Tests cover oversized and high-bit counts.

Changes

NVIDIA device count bounds

Layer / File(s)	Summary
Cap device counts and verify bounds pkg/monitor/nvidia/v0/spec.go, pkg/monitor/nvidia/v0/spec_test.go, pkg/monitor/nvidia/v1/spec.go, pkg/monitor/nvidia/v1/spec_test.go	DeviceNum returns no more than maxDevices in both versions. Tests cover oversized and high-bit counts.

Estimated code review effort: 2 (Simple) | ~5 minutes

Possibly related PRs

• Project-HAMi/HAMi#2362 — Modifies NVIDIA v0/v1 device-count handling and tests to clamp oversized shared-region counts.

Suggested reviewers: lengrongfu, fouof, dsfans2014

Poem

A rabbit checks each count,
High bits meet a sturdy mount.
V0 and v1 stay in line,
maxDevices marks the design.
Tests confirm the bound is sound.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the DeviceNum clamping fix and its purpose of preventing scrape-path panics.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@pkg/monitor/nvidia/v0/spec.go`:
- Line 81: Clamp the uint64 device count before converting it to int in both
DeviceNum implementations: update pkg/monitor/nvidia/v0/spec.go lines 81-81 and
pkg/monitor/nvidia/v1/spec.go lines 95-95 to apply min against
uint64(maxDevices), then narrow the result to int.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 39b388cc-b553-4322-863c-f301c0ae1ade

📥 Commits

Reviewing files that changed from the base of the PR and between 96207fc and da80db8.

📒 Files selected for processing (4)

• pkg/monitor/nvidia/v0/spec.go
• pkg/monitor/nvidia/v0/spec_test.go
• pkg/monitor/nvidia/v1/spec.go
• pkg/monitor/nvidia/v1/spec_test.go

[coderabbitai]

Note

GitHub couldn't provide a complete incremental comparison for this pull request, so CodeRabbit is performing a full review instead. This review may take a little longer.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Flag	Coverage Δ
unittests	62.04% <100.00%> (+0.09%)	⬆️

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

Files with missing lines	Coverage Δ
pkg/monitor/nvidia/v0/spec.go	95.45% <100.00%> (ø)
pkg/monitor/nvidia/v1/spec.go	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes

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[Eshiv-Pandey]

@Nakshatra480 just add ai disclosure. you can take ref from contributing.md

[Nakshatra480]

@Nakshatra480 just add ai disclosure. you can take ref from contributing.md

Done

[archlitchi]

/lgtm

[hami-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: archlitchi, Nakshatra480

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