Doca Dpa

DOCA DPA

Examples

• "Run compute on the DPA from my host." — this is in scope. Stay on doca_dpa + a DPACC-built image; do not rewrite it as host-CPU or GPUNetIO.

• "DPA kernel hangs, no completion." — drain doca_dpa_completion and check DOCA/DPACC version skew before changing the kernel.

Instructions

Follow Loading order below. Open the tasks companion for configure / launch / debug. Open the capabilities companion for threads vs kernels and the DPA cap query. Do not open every companion file.

Where to start: This skill assumes DOCA is already installed, the user's BlueField has a DPA processor and the host can see it through DOCA, and the user is doing hands-on DPA work from the host side — i.e. using doca-dpa to load a DPA application image, launch DPA kernels, and exchange data with the DPA processor. Open the tasks companion if the user wants to do something (configure / build / modify / run / test / debug); open the capabilities companion when the question is what can the host-side DPA API express on this version + this BlueField generation. If the user has not installed DOCA yet, route to doca-setup/SKILL.md first; if the user is asking how to write the DPA-side kernel itself (the code that runs on the DPA processor, compiled by dpacc), that is a different scope — route via doca-public-knowledge-map/SKILL.md to the public DOCA DPA / DPACC / DPA-Comms / DPA-Verbs guides (this skill does not redefine those DPA-side surfaces).

Audience

This skill serves external developers building applications that consume the DOCA DPA library from the host side — i.e., users whose code calls doca_dpa_* from host C / C++ to stand up the per-DPA-instance context, load a DPA application image that dpacc produced from their DPA-side source, create one or more DPA threads, launch DPA kernels with arguments, and drain completions. It is not for NVIDIA developers contributing to DOCA DPA itself, nor is it the place to learn how to write the DPA-side kernel code (that path goes through the public DOCA DPA, DPACC, DPA-Comms, and DPA-Verbs guides via doca-public-knowledge-map/SKILL.md).

Language scope. DOCA DPA ships as a host-side C library with pkg-config module name doca-dpa. The host-side API is C; the DPA-side kernel is a separate translation unit written in the language the DPACC compiler accepts and compiled by dpacc into a binary that the host packages into the executable as the DPA application image. The shipped samples under /opt/mellanox/doca/samples/doca_dpa/ are written in C plus DPA-side source (NVIDIA's choice). Other-language consumers are limited in practice — the DPA-side kernel has no FFI escape hatch because it must be a translation unit dpacc accepts — but a Rust / Go / Python host-side wrapper that drives doca_dpa_* setup and launches a DPA kernel image built separately is still useful, and the skill keeps the lifecycle, capability-discovery, env-precondition, and error-taxonomy guidance language-neutral.

When to load this skill

Load this skill when the user is doing hands-on DOCA DPA work from the host side, in any host language plus a DPA-side translation unit built by dpacc. Concretely:

• Initializing a doca_dpa against a doca_dev that maps to a BlueField with a DPA processor visible to the host.

• Loading a DPA application image (doca_dpa_app) that dpacc produced from the user's DPA-side source, into the doca_dpa context.

• Creating one or more DPA execution contexts (doca_dpa_thread) so DPA kernels have somewhere to run on the DPA processor.

• Launching a DPA kernel function with arguments from the host via the doca_dpa_kernel_launch_update_* family, and reasoning about which argument shape is supported on this install.

• Attaching a doca_dpa_completion to observe when async DPA work finishes, and draining it from the host side.

• Checking which DPA features are supported on the active doca_devinfo via the doca_dpa_cap_* family — BlueField generations differ in DPA hardware support.

• Debugging a DOCA_ERROR_* returned from a doca_dpa_* call — in particular disambiguating DPA not present on this BlueField from DPA feature too new for this hardware generation from DPACC-produced image mismatched against the host-side DOCA install from DPA driver layer reporting failure.

• Designing host-side bindings in a non-C language that drive a DPA application image they built separately with dpacc — the env-precondition and capability-discovery rules in this skill still apply.

"My DPA kernel hangs and I never get a completion" is a host-side question first. Launch calls are asynchronous, so a successful return means submitted, not finished. Before reading a line of kernel code, establish that the host is actually in a position to observe completion: a doca_dpa_completion is attached, and the host is driving doca_pe_progress in parallel with the outstanding launches. A host that submits and then blocks without progressing the PE sees no completions and concludes "the DPA is hung" incorrectly — the kernel may have finished already. Only once that is excluded is a non-terminating kernel body the suspect. Both steps and the ordering are in ## run steps 2-3.

• Writing DPA-side kernel code that calls the DPA device-side comm component libdoca_dpa_dev_comm.a (header doca_dpa_dev_comch_msgq.h) — for inter-DPA-thread messaging or coordination signals between DPA threads on the same doca_dpa_app. The DPA-Comms routing rule, primitive families, capability rule (there is no per-primitive host cap-query family — host-side DPA discovery is only doca_dpa_cap_is_supported / doca_dpa_cap_get_max_kernel_time_alive_supported), error overlay (_AGAIN → kernel must yield; _BAD_STATE disambiguation from the parent's host-side _BAD_STATE), and the configure / build / modify / run / test / debug overlay live in ## comms and

  comms under this same skill.

• Writing DPA-side kernel code that calls the DPA device-side verbs component libdoca_dpa_dev_verbs.a (header doca_dpa_dev_verbs.h) — for RDMA from inside the DPA kernel to a remote peer when the host round-trip is the measured latency bottleneck. The 4-way RDMA matrix, the host-configures-QP / DPA-uses-QP coupling rule, the capability rule (no per-verb host cap-query family exists; verb availability follows the BlueField generation + matched DOCA/DPACC install, read from doca_dpa_dev_verbs.h and the shipped sample), the IO_FAILED → CQE-inspection overlay, and the climb-back rule live in

  verbs and

  verbs under this same skill.

Do not load this skill for general DOCA orientation, install of DOCA or the DPACC compiler, the DPA-side programming model itself (how to write a DPA kernel; the DPA device-side comm and verbs components (libdoca_dpa_dev_comm.a / libdoca_dpa_dev_verbs.a) that run inside the DPA kernel), or non-DPA library questions. For those, route through doca-public-knowledge-map/SKILL.md to the matching upstream guide.

What this skill provides

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

• the capabilities companion — what the host-side DPA API can express on this version + this BlueField generation: the per-DPA-instance doca_dpa context, the loaded doca_dpa_app image produced by dpacc, the doca_dpa_thread execution context, the host-initiated kernel launch surface (doca_dpa_kernel_launch_update_*), the doca_dpa_completion mechanism, the capability-query surface (doca_dpa_cap_*), the DPA error taxonomy mapped onto the cross-library DOCA_ERROR_* set, the observability surface (host-side completions plus the public DPA developer tools surface reachable via doca-public-knowledge-map), and the safety policy that gates env preconditions (DPA-capable BlueField, matched DOCA + DPACC versions, DPA-side image and host-side expected entry points agree).

• the tasks companion — step-by-step workflows for the six in-scope DPA 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 where DOCA is already installed at the standard location, a BlueField with a DPA processor is physically present and visible to the host, the DPACC compiler is installed at a version matched to the DOCA install per the DOCA Compatibility Policy, and the user already knows how (at least at a sketch level) to write the DPA-side kernel that dpacc will compile. It does not cover installing DOCA or the DPACC compiler — that path goes through doca-setup/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 DPA application source code or DPA-side kernel source, in any language. The verified DPA source is the shipped C + DPA-side samples at /opt/mellanox/doca/samples/doca_dpa/. The agent's job is to route the user to those files and prescribe a minimum-diff modification on them via the universal modify-a-sample workflow in doca-programming-guide/SKILL.md, layered with the DPA-specific overrides in

  modify.

• Standalone build manifests (meson.build, CMakeLists.txt, …) parked inside the skill. The agent constructs the build manifest in the user's project directory against the user's installed DOCA + DPACC compiler, where pkg-config --modversion doca-dpa and the installed dpacc are the two sources of truth.

• A samples/, bindings/, or reference/ subtree of any kind. A mock or incomplete artifact in this skill's tree, even one labeled "reference", is misleading: users will read it as buildable.

• DPA device-side content for the comm / verbs components (libdoca_dpa_dev_comm.a / libdoca_dpa_dev_verbs.a). These are DPA-side archives shipped as part of doca-dpa (NOT separate pkg-config modules): their symbols are called from inside the DPA kernel and linked into the DPA image by dpacc, not from the host. Their public guides are reachable via doca-public-knowledge-map/SKILL.md. This skill names them and routes; it does not redefine them.

Loading order

1. Read this skill first to confirm the user's question is in scope (host-side DPA work, not DPA-side kernel-writing).

2. For the DPA capability matrix, the doca_dpa per-instance context, the loaded doca_dpa_app image, the doca_dpa_thread execution context, the kernel-launch + completion model, the dual capability query, 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, doca-version/SKILL.md for the canonical DOCA version-handling rules (with the DPA overlay that DOCA must match the DPACC compiler), and doca-public-knowledge-map/SKILL.md whenever the right answer is "look it up in the public DOCA DPA, DPACC, DPA-Comms, or DPA-Verbs guide, or in the on-disk install layout" rather than "DPA host-side-specific guidance".

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 DPA public guide is at https://docs.nvidia.com/doca/sdk/DOCA-DPA/index.html; the DPACC compiler guide, the DPA-Comms guide (DPA-side communications), the DPA-Verbs guide (DPA-side verbs), and the DPA Tools umbrella (developer / admin CLIs for DPA) live in the same routing table and are companion surfaces to this skill rather than redefined by it.

• doca-setup/SKILL.md — env preparation, install verification, DPACC compiler install / verification, and the I have no install yet path with the public NGC DOCA container. This skill assumes its preconditions are satisfied AND that DPACC is installed at a version that matches DOCA.

• doca-version/SKILL.md — canonical DOCA version-handling rules. This skill's ## Version compatibility cross-links the four-way match rule and adds the DPA-specific DOCA-and-DPACC must match overlay per the DOCA Compatibility Policy.

• 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 — shared build, first-app, Core-lifecycle and cross-library DOCA_ERROR_* patterns; this skill layers DPA specifics on top.

• doca-debug/SKILL.md — the cross-cutting debug ladder; this skill's ## debug adds the DPA overlay (DOCA + DPACC skew, no DPA on this BlueField, kernel hangs with no host-side completion, launch-argument / signature mismatch).

DPA device-side components

DOCA DPA's DPA device-side components — the comm archive libdoca_dpa_dev_comm.a (communication primitives the DPA kernel itself calls, header doca_dpa_dev_comch_msgq.h) and the verbs archive libdoca_dpa_dev_verbs.a (ibverbs-like RDMA verbs the DPA kernel itself calls, header doca_dpa_dev_verbs.h) — are DPA-side archives shipped within doca-dpa, not separate pkg-config modules, and each has its own public guide. This skill covers them in its ## comms / ## verbs sections; for per-symbol detail, route via doca-public-knowledge-map/SKILL.md to the public DOCA DPA Comms and DOCA DPA Verbs guides and to the shipped /opt/mellanox/doca/samples/doca_dpa/ samples (which include both host-side and DPA-side translation units). Conflating them with doca-dpa is the single most common DPA first-app design error.