fix(nvlink): Multicast group limit attribute, when creating a partiti…

[rtamma-nv]

…on, needs to be a multiple of 4.

GB200 NVL partition multicast group limit setting has an additional constraint that the value must be 0 or a multiple of 4. The formula previously used to calculate the default limit was evaluating to a value of 18. This PR rounds it down to nearest multiple of 4.
NMX-C simulator used for pre-integration testing does not check for this contraint.

Related issues

Type of Change

• Add - New feature or capability
• Change - Changes in existing functionality
• [ X] Fix - Bug fixes
• Remove - Removed features or deprecated functionality
• Internal - Internal changes (refactoring, tests, docs, etc.)

Breaking Changes

• This PR contains breaking changes

Testing

• Unit tests added/updated
• Integration tests added/updated
• [ X] Manual testing performed
• No testing required (docs, internal refactor, etc.)

Additional Notes

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📥 Commits

Reviewing files that changed from the base of the PR and between 6d36a43 and 72228fb.

📒 Files selected for processing (1)

• crates/nvlink-manager/src/lib.rs

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Summary by CodeRabbit

• Bug Fixes
  • Optimized multicast groups limit configuration for partition creation, adjusting it to a fixed value for improved stability and consistency.

Walkthrough

NMX_C_PARTITION_MULTICAST_GROUPS_LIMIT in crates/nvlink-manager/src/lib.rs is changed from the integer-division expression 1024 / (36 + 18) to a hardcoded constant of 16. The associated comment is updated to describe the "multiple of 4" and tray/partition assumptions that produce this value.

Changes

NMX-C Multicast Groups Limit Fix

Layer / File(s)	Summary
Hardcode multicast groups limit to 16 crates/nvlink-manager/src/lib.rs	NMX_C_PARTITION_MULTICAST_GROUPS_LIMIT is changed from the computed expression 1024 / (36 + 18) to a fixed value of 16; the comment is revised to state the multiple-of-4 and tray/partition assumptions that yield that value.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the primary change: fixing the multicast group limit attribute to be a multiple of 4 when creating partitions, which addresses the core objective of the PR.
Description check	✅ Passed	The description is directly related to the changeset, explaining the constraint violation, the previous calculated value of 18, the rounding to 16, and the testing approach undertaken.
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.

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[github-actions]

🔍 Container Scan Summary

Service	Total	Critical	High	Medium	Low	Other
boot-artifacts-aarch64	3	0	0	3	0	0
boot-artifacts-x86_64	3	0	0	3	0	0
forge-admin-cli-x86_64	245	5	22	103	6	109
machine-validation-runner	675	31	182	255	37	170
machine_validation	675	31	182	255	37	170
nvmetal-carbide	675	31	182	255	37	170
TOTAL	2276	98	568	874	117	619

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