| .. SPDX-License-Identifier: GPL-2.0-or-later |
| |
| ========= |
| vfio-user |
| ========= |
| |
| QEMU includes a ``vfio-user`` client. The ``vfio-user`` specification allows for |
| implementing (PCI) devices in userspace outside of QEMU; it is similar to |
| ``vhost-user`` in this respect (see :doc:`vhost-user`), but can emulate arbitrary |
| PCI devices, not just ``virtio``. Whereas ``vfio`` is handled by the host |
| kernel, ``vfio-user``, while similar in implementation, is handled entirely in |
| userspace. |
| |
| For example, SPDK includes a virtual PCI NVMe controller implementation; by |
| setting up a ``vfio-user`` UNIX socket between QEMU and SPDK, a VM can send NVMe |
| I/O to the SPDK process. |
| |
| Presuming a suitable ``vfio-user`` server has opened a socket at |
| ``/tmp/vfio-user.sock``, a device can be configured with for example: |
| |
| .. code-block:: console |
| |
| -device '{"driver": "vfio-user-pci","socket": {"path": "/tmp/vfio-user.sock", "type": "unix"}}' |
| |
| See `libvfio-user <https://github.com/nutanix/libvfio-user/>`_ for further |
| information. |
