Doca Urom

DOCA UROM

Examples

• "Push UCX traffic onto the BlueField." — this is in scope. Stay on host-side doca-urom; do not deploy the DPU-side UROM Service here.

• "First doca_urom call returns NOT_PERMITTED." — check host/service version alignment and the RDMA substrate first.

Instructions

Follow Loading order below. Open the tasks companion for configure / offload / debug. Open the capabilities companion for service vs worker contexts. Do not open every companion file.

Where to start: This skill assumes DOCA is installed on both host and BlueField, the DOCA UROM Service is deployed and running on the BlueField, and the user is doing hands-on UROM work from the host side — using doca-urom from an HPC / UCX / MPI stack to enqueue remote memory operations (puts, gets, atomics, active messages, collectives) the DPU executes on the host's behalf. Open the tasks companion to do something (configure / build / modify / run / test / debug); open the capabilities companion for what the host-side UROM API expresses on this version + BlueField + UROM Service version. If DOCA is not installed, route to doca-setup/SKILL.md first; for the DPU-side UROM Service itself (deployment, container, lifecycle), that is a DIFFERENT artifact — route via doca-public-knowledge-map ## DOCA services (doca-public-knowledge-map/SKILL.md#doca-services) to the public DOCA UROM Service guide. This skill is the host-side library; the UROM Service is the DPU-side executor; they are a paired contract.

How to use this skill. Read this file, then search the companion file for the ## <name> heading the question needs and read that whole section. Answer completely from it, quoting only its symbols and commands. Do not browse docs; use the entry points in doca-public-knowledge-map. For out-of-scope requests, name the skill that owns them and stop.

Example questions this skill answers well

The CLASSES of UROM questions this skill answers, each with one worked example. The class is the load-bearing piece; the worked example is one instance.

• "How do I offload my MPI / UCX remote memory operations from the host CPU to the BlueField?" — worked example: "my MPI all-reduce burns host CPU cycles I'd rather use for compute — how do I push that onto the BlueField via UROM?". Answered by the paired-contract model in the capabilities companion

  • the host-side bring-up workflow in the tasks companion.

• "Is the DOCA UROM Service even running on my BlueField, and why does that matter before I write doca_urom_* code?" — worked example: "my first doca_urom_* call returns DOCA_ERROR_NOT_PERMITTED on an otherwise-healthy host". Answered by the env-precondition matrix in the capabilities companion

  • the service-deployed check in the tasks companion step 1, which routes service-side env questions to doca-public-knowledge-map ## DOCA services (doca-public-knowledge-map/SKILL.md#doca-services).

• "Is this UROM operation type / atomic / collective supported on my device + DOCA install + UROM Service version?" — worked example: "does my BlueField support remote atomic Fetch-and-Add for an MPI window?". Answered by the plugin-discovery rule (doca_urom_service_get_plugins_list on a started Service — UROM operations are plugin-defined Command tasks, so the plugins list is the capability surface) in the capabilities companion

  • the discovery step in the tasks companion.

• "How does doca-urom relate to doca-rdma — am I replacing it, layering on top, or something else?" — worked example: "I already have raw doca-rdma working; should I rewrite to use UROM?". Answered by the path-selection rule in the capabilities companion (UROM rides the RDMA substrate but adds the DPU-offload contract; it is the right tool only when host CPU is the bottleneck — simple point-to-point cases stay on doca-rdma).

• "Is this UROM API on my installed DOCA version?" — worked example: "is the collective-ops plugin discoverable via doca_urom_service_get_plugins_list on DOCA 3.x". Answered by the version-compatibility overlay in the capabilities companion, which cross-links the canonical detection chain in doca-version/SKILL.md and adds the host library + DPU service versions must match overlay.

• "What does this DOCA_ERROR_* from a doca_urom_* call mean and which layer caused it?" — worked example: "DOCA_ERROR_NOT_PERMITTED on the first enqueue after doca_ctx_start() succeeded". Answered by the UROM overlay on the cross-library taxonomy in the capabilities companion

  • the layered ladder in the tasks companion that escalates to doca-debug/SKILL.md.

Audience

This skill serves external developers building HPC / UCX / MPI applications that consume the DOCA UROM library from the host side — code calling doca_urom_* (directly in C / C++, through FFI / bindings, or through a UCX-based stack such as OpenMPI / MPICH wired to use UROM as a transport) to push remote memory operations onto the BlueField instead of the host CPU. It is not for NVIDIA developers contributing to DOCA UROM, nor the place to learn how to deploy / operate the UROM Service on the DPU side — that goes through the public DOCA UROM Service guide via doca-public-knowledge-map ## DOCA services (doca-public-knowledge-map/SKILL.md#doca-services).

Language scope. DOCA UROM ships as a host-side C library (pkg-config module doca-urom); shipped samples under /opt/mellanox/doca/samples/doca_urom/ are C. C / C++ consumers — including UCX-based stacks wrapping the library — are the canonical case the tasks companion assumes. Other-language consumers (Rust, Go, Python, …) reach the same *.so through FFI; the skill keeps its lifecycle, capability-discovery, error-taxonomy, and RDMA-substrate guidance language-neutral and routes to the public C ABI as the authoritative surface.

When to load this skill

Load this skill when the user is doing hands-on DOCA UROM work from the host side, in any language. Concretely:

• Initializing a UROM Service context (doca_urom_service_*) on a doca_dev mapping to the target BlueField, creating Worker contexts (doca_urom_worker_*) attached to it, and confirming the matching DPU-side UROM Service is reachable before the first enqueue.

• Enqueueing remote memory operations (puts, gets, atomics, active messages, collectives) through doca_urom_* and progressing the DOCA progress engine for completions.

• Calling doca_urom_service_get_plugins_list on a started Service to discover which plugins — and therefore which operation types / atomics / collectives, since these are plugin-defined — this device + DOCA install + UROM Service version supports.

• Applying the UROM lifecycle, capability-discovery, and error rules to a UCX-based HPC stack (OpenMPI, MPICH, custom UCX consumer) already wired to use UROM. Designing the UCX transport integration itself remains upstream-stack work.

• Debugging a DOCA_ERROR_* from doca_urom_* — disambiguating DPU-side UROM Service unreachable vs operation type unsupported on this device vs plain doca_dev access denied vs underlying RDMA transport failure.

• Designing non-C bindings (Rust, Go, Python, …) that wrap the UROM C ABI and must honor the same lifecycle and error rules.

Do not load this skill for general DOCA orientation, DOCA install, deployment / operation of the DPU-side UROM Service (a separate artifact with its own public guide via doca-public-knowledge-map ## DOCA services (doca-public-knowledge-map/SKILL.md#doca-services)), or non-UROM library questions. For those, use doca-public-knowledge-map/SKILL.md.

What this skill provides

This is a thin loader. The body keeps only the orientation needed to pick the right next file. The substantive UROM-specific material lives in two companion files:

• the capabilities companion — what the host-side UROM API expresses on this version + BlueField + UROM Service version: the paired-contract model (host enqueues; DPU service executes); the two context types (doca_urom_service — one per BlueField, bound to its doca_dev — and attached doca_urom_worker contexts); the enqueue-side operation surface (puts, gets, atomics, active messages, collectives) delivered as plugin-defined Worker Command tasks, named generically because exact symbol shapes are plugin- and install-bound; the plugin-discovery surface (doca_urom_service_get_plugins_list); the UROM error taxonomy mapped onto DOCA_ERROR_*; the observability surface (completion events, capability snapshots, RDMA counters); and the safety policy gating env preconditions (UROM Service deployed on the DPU; host library + DPU service versions agree; RDMA-capable BlueField + DOCA install).

• the tasks companion — step-by-step workflows for the six in-scope UROM verbs: configure, build, modify, run, test, debug. Plus a Deferred task verbs block that points out-of-scope questions at the right next skill.

The skill assumes a host + BlueField pair where DOCA is installed, the UROM Service is deployed and running on the BlueField, the RDMA transport between them is healthy, and the user has a sketch of the HPC / UCX / MPI stack to offload. It does not cover installing DOCA, deploying the UROM Service container, or bringing up RDMA / RoCE / IB transport — those go through doca-setup/SKILL.md, the public DOCA UROM Service guide, and doca-rdma/SKILL.md.

What this skill deliberately does not ship

This skill is agent guidance, not a samples or templates bundle. To keep the boundary clean, it deliberately does not contain — and pull requests should not add:

• Pre-written DOCA UROM application source code, in any language. The verified UROM source is the shipped C samples at /opt/mellanox/doca/samples/doca_urom/. The agent routes the user there and prescribes a minimum-diff modification via the modify-a-sample workflow in doca-programming-guide/SKILL.md, layered with the UROM overrides in the tasks companion.

• An MPI / UCX algorithm or collective implementation. This library offloads remote memory operations; picking which puts / gets / atomics / collectives to issue for a given MPI primitive is the user's HPC stack or domain expertise. Refuse to invent collective algorithms; route "what algorithm should my all-reduce use" to upstream MPI / UCX docs — that is a stack-design question, not a UROM API question.

• Standalone build manifests (meson.build, CMakeLists.txt, Cargo.toml, …) parked inside the skill. The agent constructs the manifest in the user's project against the installed DOCA, where pkg-config --modversion doca-urom is the source of truth.

• A samples/, bindings/, or reference/ subtree of any kind. A mock artifact labeled "reference" reads as buildable and misleads.

• The DOCA UROM Service surface. That service is a separate artifact with its own public guide; routing lives in doca-public-knowledge-map ## DOCA services (doca-public-knowledge-map/SKILL.md#doca-services). Conflating the library (host-side enqueue) with the service (DPU-side executor) is the most common UROM first-app design error.

Loading order

1. Read this skill first to confirm the user's question is in scope (host-side library work; not DPU-side service deployment, and not MPI / UCX algorithm design).

2. For the UROM capability matrix, the paired-contract model (host library + DPU service), the Service + Worker context model, the enqueue-side operation surface, the plugin-discovery rule, the env-precondition policy, the error taxonomy, the observability surface, and the safety policy, see the capabilities companion.

3. For step-by-step workflows — configure, build, modify, run, test, debug — see the tasks companion.

Both companion files cross-link to each other, to doca-version/SKILL.md for canonical version rules (with the UROM overlay that host library and DPU service versions must match), to doca-rdma/SKILL.md for the underlying RDMA substrate, and to doca-public-knowledge-map/SKILL.md whenever the right answer is "look it up in the public UROM library / Service guide or the on-disk install layout".

Related skills

• doca-public-knowledge-map/SKILL.md — the routing table for every public DOCA documentation source and the on-disk layout of an installed DOCA package. The DOCA UROM library public guide is at https://docs.nvidia.com/doca/sdk/DOCA-UROM/index.html; the DOCA UROM Service is a different artifact documented separately under the DOCA services section of that map.

• doca-rdma/SKILL.md — the underlying RDMA transport substrate the BlueField uses to move bytes once UROM offloads an operation. UROM does NOT replace RDMA; it adds the DPU-offload contract on top. For simple point-to-point RDMA where host CPU is not the bottleneck, use doca-rdma directly — UROM's service-side contract is not worth its overhead there.

• doca-setup/SKILL.md — env preparation, install verification, BlueField setup, and the no install yet path via the public NGC DOCA container. This skill assumes its preconditions hold AND the DPU-side UROM Service is deployed and running.

• doca-version/SKILL.md — canonical DOCA version-handling rules. This skill's ## Version compatibility cross-links the four-way match rule and adds the host library + DPU service must agree on version overlay.

• doca-structured-tools-contract/SKILL.md — the bundle's structured-tools precedence rule (detect / prefer / fall back / report). The Command appendix in the tasks companion honors this contract.

• doca-programming-guide/SKILL.md — general DOCA programming patterns shared by every library: pkg-config + meson build, modify-a-shipped-sample first-app, Core-context lifecycle, the cross-library DOCA_ERROR_* taxonomy, and the debug order. This skill layers UROM specifics on top.

• doca-debug/SKILL.md — the cross-cutting debug ladder (install / version / build / link / runtime / program / driver). UROM-specific debug (UROM Service not reachable, host library + DPU service version skew, RDMA transport failure underneath, operation type unsupported on this device + firmware + service version) overlays on top.

The DOCA UROM Service running on the DPU side is deliberately not in scope — a separate artifact with its own public guide via doca-public-knowledge-map ## DOCA services (doca-public-knowledge-map/SKILL.md#doca-services). Conflating the library and the service is the single most common UROM first-app design error: surface the split explicitly whenever a question straddles the two.