[ROCm][P/D] Fix MoRIIO WRITE mode for mixed KV layouts

[tanpinsiang]

Summary

This PR adds the WRITE-mode counterpart to #46039.

#46039 made MoRIIO READ mode layout-aware for mixed KV cache layouts. WRITE mode still had two correctness issues:

1. It reused one request-wide offset tuple across layers, which is incorrect when dense K/V layers and key-only/indexer layers have different cache geometry.
2. It counted registered cache tensors for WRITE completion, instead of counting the layers actually scheduled by the WRITE hook.

This PR fixes MoRIIO WRITE correctness for mixed KV layouts by computing offsets per KV cache geometry and completing requests based on scheduled WRITE work.

Changes

• Compute WRITE transfer offsets per geometry in MoRIIOWriter._prepare_transfer_plan.
• Cache WRITE offset plans by KV cache geometry instead of reusing one request-wide tuple.
• Track scheduled WRITE layers per transfer_id, deduplicate repeated layer scheduling, and notify decode exactly once after all scheduled writes finish.
• Add typed MoRIIO control messages for remote_blocks, write_done, and release.
• Keep backward-compatible plain string notification handling.
• Clarify the producer-block release path when decode finishes before remote allocation metadata exists.
• Resolve kernel-block KV cache geometry through the layer attention spec instead of assuming a fixed block dimension.

Tests

Adds unit coverage for:

• WRITE offset caching,
• scheduled-write completion accounting,
• structured and plain notification handling,
• producer-block release handling,
• kernel-block layout geometry.

Validation

MoRIIO unit tests: 31 passed

Primary E2E validation used MiniMaxAI/MiniMax-M3-MXFP8 on MI350X TP4+TP4:

• Accuracy: GSM8K, 25-shot, 32 concurrent, all 1319 prompts.
• Benchmark: random 1024 input / 1024 output, concurrency 10, 500 prompts.
• Benchmark servers used --no-enable-prefix-caching

Mode	Backend	GSM8K flexible	GSM8K strict	Req/s	Output tok/s	Total tok/s	Mean TTFT	Mean TPOT
WRITE	XGMI	0.9515 +/- 0.0059	0.9522 +/- 0.0059	0.4424	452.97	905.95	216.64 ms	21.87 ms
WRITE	RDMA	0.9507 +/- 0.0060	0.9515 +/- 0.0059	0.4428	453.42	906.83	216.77 ms	21.84 ms
READ regression	XGMI	0.9560 +/- 0.0056	0.9568 +/- 0.0056	0.4404	450.93	901.85	174.23 ms	22.01 ms
READ regression	RDMA	0.9553 +/- 0.0057	0.9560 +/- 0.0056	0.4414	451.97	903.93	180.51 ms	21.95 ms

Cross-model WRITE on the same TP4+TP4 same-container P/D shape:

• GSM8K, 25-shot, 32 concurrent.
• AITER enabled

Model	Backend	GSM8K flexible	GSM8K strict
Qwen3-235B-A22B-FP8	XGMI	0.8355 +/- 0.0102	0.7248 +/- 0.0123
Qwen3-235B-A22B-FP8	RDMA	0.8362 +/- 0.0102	0.7286 +/- 0.0122
DeepSeek-V2-Chat-0628	XGMI	0.8036 +/- 0.0109	0.6270 +/- 0.0133
DeepSeek-V2-Chat-0628	RDMA	0.8074 +/- 0.0109	0.6149 +/- 0.0134

This PR does not include heterogeneous TP rank mapping or READ ACK fan-in / duplicate ACK handling; those remain separate PR.

This PR is co-authored by
@vllmellm @hongxiayang @junkang1991 @tanpinsiang @chunfangamd @TianDi101 @functionstackx.

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[tanpinsiang]

@inkcherry @dllehr-amd could you help to review this?

[tjtanaa]

LGTM. The changes are well isolated to just the moriio files and the PR provides proper test results across different backend and models.

[mergify]

Hi @tanpinsiang, the pre-commit checks have failed. Please run:

uv pip install pre-commit>=4.5.1
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

[depthfirst-app]

🟡 Severity: MEDIUM

The new _send_transfer_release method creates outbound ZMQ TCP connections to host:port. These values originate from kv_transfer_params (via _release_write_prefill_blocks), which is a user-controlled dict[str, Any] exposed in the OpenAI-compatible API. An attacker can supply arbitrary remote_host/remote_notify_port values to make the server connect to internal services.
Helpful? Add 👍 / 👎

💡 Fix Suggestion

Suggestion: Add validation for host and port parameters before creating outbound ZMQ connections. This should be done consistently across all methods that accept user-supplied host/port values (_send_transfer_release, send_notify_block, and _release_write_prefill_blocks). Recommended approaches:

1. Host allowlist: Maintain a set of known/trusted peer hosts (populated during engine initialization or handshake) and reject any remote_host not in the allowlist.
2. IP range validation: At minimum, validate that the host is a well-formed IP/hostname and reject private/loopback ranges if the deployment expects only specific network segments (e.g., using ipaddress.ip_address() to parse and check against allowed networks).
3. Port range validation: Ensure the port is within the expected port range for MoRIIO notify ports.
4. Centralized validation helper: Create a shared _validate_remote_address(host, port) method on the connector class that all outbound connection methods call before make_zmq_path. This avoids duplicating validation logic across send_notify_block (line 381), _send_transfer_release (line 400), and update_state_after_alloc (line ~495).

Example validation in _send_transfer_release:

def _send_transfer_release(self, transfer_id: TransferId, host: str, port: int):
    if not self._is_trusted_peer(host, port):
        logger.warning("Rejecting connection to untrusted peer %s:%d", host, port)
        return
    path = make_zmq_path("tcp", host, port)
    ...

Where _is_trusted_peer checks against a set of known peer addresses populated during the engine handshake phase.

[inkcherry]

thanks @tanpinsiang LGTM

[hongxiayang]

great. anything else needs to be addressed before merging?