doca-devemu

DOCA Device Emulation

Examples

• "Expose a custom PCIe device from BlueField to the host." — this is in scope. Pick PCI Generic / virtio-net / virtio-fs; do not stand up SNAP or Virtio-net Service here.
• "lspci does not show my emulated device." — confirm the firmware emulation type and host driver before changing DPU-side code.

Instructions

Follow Loading order below. Open the tasks companion for configure / emulate / debug. Open the capabilities companion for sub-libraries and cap queries. Do not open every companion file.

Where to start: This skill assumes DOCA is already installed on the host AND on the BlueField, the user is doing hands-on emulated-PCIe-device work from the DPU side (writing the backend that the host's kernel driver will talk to over the emulated PCIe surface), and the user knows which CLASS of emulated device they want to build. 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 Device Emulation express on this DOCA version + this BlueField generation + this firmware. If the user has not installed DOCA yet, route to doca-setup/SKILL.md first. Before anything else, the agent must route the user to the right sub-library — DOCA Device Emulation is an umbrella that covers PCI Generic (raw PCIe device emulation), virtio-net (emulated virtio network device), and virtio-fs (emulated virtio filesystem device); each sub-library has its own context, its own pkg-config module, and its own capability surface. The sub-library selection rule lives in the capabilities companion. If the user wants a packaged solution rather than a library (e.g. "I want NVMe SNAP on my host without writing the backend myself", or "I want a managed virtio-net daemon"), route via doca-public-knowledge-map/SKILL.md to the DOCA SNAP Service / DOCA Virtio-net Service guides — those services are built on top of this library and are a different artifact than what this skill covers.

Audience

This skill serves external developers building applications that consume the DOCA Device Emulation library — i.e., users whose DPU-side code calls doca_devemu_pci_*, doca_devemu_virtio_*, or doca_devemu_vfs_* (directly in C / C++, or through FFI / bindings from another language) to expose an emulated PCIe device to the host that the host's existing kernel drivers can drive as if it were a real PCIe peripheral. It is not for NVIDIA developers contributing to DOCA Device Emulation itself, and it is not the right artifact for users who want a packaged emulated-device daemon they do not have to write the backend for (the DOCA SNAP Service and the DOCA Virtio-net Service are the packaged options that build on top of this library).

Language scope. DOCA Device Emulation ships as a C library; this skill covers three sub-libraries end-to-end. Select the exact installed pkg-config module for the user's emulation class (see the sub-library selection table in the capabilities companion). The shipped samples under /opt/mellanox/doca/samples/doca_devemu/ are written in C. C and C++ consumers are the canonical case and the worked examples in the tasks companion assume that path. Other-language consumers (Rust, Go, Python, …) consume the same *.so files through FFI or language-specific bindings; the skill's contribution in that case is to keep the sub-library selection, umbrella lifecycle, capability-discovery, permission, and error-taxonomy guidance language-neutral, and to route the agent to the public C ABI as the authoritative surface that any wrapper will eventually call.

When to load this skill

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

• Deciding which Device Emulation sub-library (PCI Generic, virtio-net, virtio-fs) the user needs — the umbrella selection question is this skill's load-bearing first move.
• Initializing the per-sub-library DOCA Core context on the DPU (one context per emulated device per sub-library) and configuring the doorbell / DMA primitives the host's PCIe driver will interact with.
• Reading per-sub-library capability surface via the doca_devemu_pci_cap_*, doca_devemu_virtio_cap_*, or doca_devemu_vfs_cap_* query families against the active doca_devinfo BEFORE assuming a particular feature bit or device characteristic is available.
• Choosing between writing the backend with doca-devemu yourself and adopting a packaged service (DOCA SNAP Service / DOCA Virtio-net Service) that already wraps this library.
• Debugging a DOCA_ERROR_* returned from a doca_devemu_* call — in particular disambiguating firmware-level emulation type not enabled from BlueField generation does not support this sub-library at all from DPU-side process lacks privilege from host-side kernel driver did not bind.
• Designing or extending non-C bindings (Rust, Go, Python, …) that wrap one of the device-emulation sub-libraries — for the sub-library selection, umbrella lifecycle, capability- discovery, permission, and error-taxonomy rules the wrapper must honor.

Do not load this skill for general DOCA orientation, install of DOCA itself, the host-side kernel driver for the emulated device class (virtio-net / virtio-blk / virtio-fs kernel drivers ship with the host kernel and are not part of DOCA), the packaged SNAP / Virtio-net services (they are separate artifacts with their own service guides), or for standard NIC behavior on the BlueField data path (use doca-flow/SKILL.md + doca-eth/SKILL.md instead — Device Emulation is for custom emulated devices, not for shaping the BlueField's built-in NIC personality).

What this skill provides

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

• the capabilities companion — what Device Emulation can express on this version + this BlueField generation + this firmware: the umbrella architecture (host sees an emulated PCIe device; DPU runs the backend), the sub-library selection rule (PCI Generic vs virtio-net vs virtio-fs), the per- sub-library Core context shape, the doorbell / DMA primitives that bridge host ↔ DPU, the per-sub-library capability-query family (doca_devemu_*_cap_*), the per-sub-library pkg-config module name, the Device Emulation error taxonomy mapped onto the cross-library DOCA_ERROR_* set, the observability surface, the library-vs-packaged-service path-selection rule, and the safety policy that gates env preconditions (DPU-side privileges, BlueField firmware-level emulation type enablement, BlueField generation actually supporting the emulation class).
• the tasks companion — step-by-step workflows for the six in-scope Device Emulation 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 already installed at the standard location on both sides, the BlueField firmware has the emulation type the user wants to build enabled, the user has the privileges their public install profile expects (in particular, sudo on the DPU side to perform PCIe-level emulation), and the host kernel ships the standard driver for the emulated device class the user is building. It does not cover installing DOCA, flipping firmware-level configuration, or installing host-side kernel drivers — those paths go through doca-setup/SKILL.md.

Loading order

1. Read this skill first to confirm the user's question is in scope (custom emulated PCIe device built on the doca-devemu library, not the packaged SNAP / Virtio-net services, not the host-side kernel driver, not standard NIC behavior).
2. For the umbrella architecture, the sub-library selection rule (PCI Generic vs virtio-net vs virtio-fs), the per- sub-library Core context shape, the doorbell / DMA primitives, the per-sub-library capability-query rule, the per-sub-library pkg-config modules, the library-vs- packaged-service path-selection rule, 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 Device Emulation overlay that the chosen sub-library's pkg-config module plus the firmware-level emulation slot plus the doca_devemu_*_cap_* query are all part of "is this emulation supported here"), and doca-public-knowledge-map/SKILL.md whenever the right answer is "look it up in the public DOCA Device Emulation umbrella guide, the per-sub-library guide linked from it, the DOCA SNAP / Virtio-net Service guide, or in the on-disk install layout" rather than "Device Emulation- 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 Device Emulation umbrella URL is https://docs.nvidia.com/doca/sdk/DOCA-Device-Emulation/index.html; per-sub-library guides are linked from the umbrella, and the packaged DOCA SNAP / Virtio-net services are listed under the DOCA Services umbrella as separate artifacts.
• doca-setup/SKILL.md — env preparation, install verification, DPU-side privilege checks, BlueField firmware configuration (including the per-sub-library emulation type enable), and the I have no install yet path with the public NGC DOCA container. This skill assumes its preconditions are satisfied AND that the firmware-level emulation type for the user's chosen sub-library is enabled.
• doca-version/SKILL.md — canonical DOCA version-handling rules. This skill's Version compatibility overlay cross-links the four-way match rule and adds the Device Emulation-specific per-sub-library pkg-config + doca_devemu_*_cap_* 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: the canonical pkg-config + meson build pattern, the universal modify-a-shipped-sample first-app workflow, the universal Core-context lifecycle, the cross-library DOCA_ERROR_* taxonomy, and the program-side debug order. This skill layers Device Emulation specifics on top.
• doca-comch/SKILL.md — the right library when the user wants a control-plane channel between a host process and a DPU process over PCIe but does NOT want the host to see the DPU as an emulated PCIe device with a standard host kernel driver. Device Emulation hides the DPU behind a real-looking PCIe device class; Comch is an explicit host ↔ DPU IPC.
• doca-flow/SKILL.md and doca-eth/SKILL.md — the right libraries when the user wants to shape traffic on the BlueField's built-in NIC personality, not expose a custom emulated PCIe device. Device Emulation is for new emulated PCIe devices the host did not previously see; Flow / Eth are for the BlueField's existing NIC surface.
• doca-debug/SKILL.md — the cross-cutting debug ladder (install / version / build / link / runtime / program / driver). Device Emulation-specific debug (firmware-level emulation type not enabled, sub-library mis-selected, host kernel driver not binding to the emulated device, virtio feature-negotiation failures) overlays on top of that ladder.