VDUSE userspace-backed vDPA virtual devices
VDUSE is a kernel framework letting userspace programs implement virtual devices (network, block, virtio-fs) that appear to the system as vDPA devices. It is used by QEMU's storage daemon, which exposes a vduse-blk export so userspace block backends can be attached to virtual machines without dedicated hardware.
recommendation
It should stay in the kernel because VDUSE is an actively developed virtualization framework, not legacy hardware support. The directory has been receiving substantive feature work through 2025 (virtqueue groups, ASID support, virtio-fs enablement, map API changes), and userspace tooling — notably QEMU's storage daemon, which has shipped vduse-blk since QEMU 7.1 — depends on it. Deployments are niche but real, and there is no in-tree replacement filling the same role.
repository signals
sources
- docs.kernel.org
Current kernel documentation describes VDUSE as a supported framework for implementing software-emulated vDPA devices in userspace, with current uAPI details including ASID support.
- qemu.org
Current QEMU storage-daemon documentation exposes a `vduse-blk` export type and documents attaching the resulting device to the vDPA bus via `vdpa dev add ... mgmtdev vduse`, indicating ongoing real-world virtualization/storage use.
- qemu.org
Current QEMU QMP reference lists `BlockExportOptionsVduseBlk` and records `vduse-blk` support since QEMU 7.1, showing the userspace ecosystem still carries first-class support for this path.
- git.kernel.org
Canonical kernel git log location for this directory; local tree history sample shows nontrivial VDUSE changes landing through 2026 rather than abandonment.
codex reasoning notes (technical)
`drivers/vdpa/vdpa_user` is a real driver directory, but it is not tied to a physical chipset: local inspection via `exec_command` showed `vduse_dev.c`, char-device plumbing, and `module_init`, matching the VDUSE userspace-backed vDPA framework. No lore removal/deprecation evidence was found from `web.search_query` attempts against `lore.kernel.org`; local git history gathered with `exec_command` instead showed active 2025-2026 feature/fix traffic (`vq group support`, `asid support`, `virtio_fs` allowance, map API work), so this is not a dead legacy driver. The kernel-doc URL was obtained via `web.search_query`; the two QEMU URLs were obtained via `web.search_query`; the git.kernel.org log URL is a canonical stable page included by canonical recall and used to anchor the local-history claim. Because VDUSE serves a specialized virtual-device/storage niche rather than shipping hardware, `hardware_still_sold_new_in_2025` is false, deployments are `low` rather than none, and there is no direct upstream replacement driver for the same kernel role.