xref: /qemu/docs/system/devices/vfio-user.rst (revision aec6836c73403cffa56b9a4c5556451ee16071fe)
1*c688cc16SJohn Levon.. SPDX-License-Identifier: GPL-2.0-or-later
2*c688cc16SJohn Levon
3*c688cc16SJohn Levon=========
4*c688cc16SJohn Levonvfio-user
5*c688cc16SJohn Levon=========
6*c688cc16SJohn Levon
7*c688cc16SJohn LevonQEMU includes a ``vfio-user`` client. The ``vfio-user`` specification allows for
8*c688cc16SJohn Levonimplementing (PCI) devices in userspace outside of QEMU; it is similar to
9*c688cc16SJohn Levon``vhost-user`` in this respect (see :doc:`vhost-user`), but can emulate arbitrary
10*c688cc16SJohn LevonPCI devices, not just ``virtio``. Whereas ``vfio`` is handled by the host
11*c688cc16SJohn Levonkernel, ``vfio-user``, while similar in implementation, is handled entirely in
12*c688cc16SJohn Levonuserspace.
13*c688cc16SJohn Levon
14*c688cc16SJohn LevonFor example, SPDK includes a virtual PCI NVMe controller implementation; by
15*c688cc16SJohn Levonsetting up a ``vfio-user`` UNIX socket between QEMU and SPDK, a VM can send NVMe
16*c688cc16SJohn LevonI/O to the SPDK process.
17*c688cc16SJohn Levon
18*c688cc16SJohn LevonPresuming a suitable ``vfio-user`` server has opened a socket at
19*c688cc16SJohn Levon``/tmp/vfio-user.sock``, a device can be configured with for example:
20*c688cc16SJohn Levon
21*c688cc16SJohn Levon.. code-block:: console
22*c688cc16SJohn Levon
23*c688cc16SJohn Levon-device '{"driver": "vfio-user-pci","socket": {"path": "/tmp/vfio-user.sock", "type": "unix"}}'
24*c688cc16SJohn Levon
25*c688cc16SJohn LevonSee `libvfio-user <https://github.com/nutanix/libvfio-user/>`_ for further
26*c688cc16SJohn Levoninformation.
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