linux-imx

.. include:: <isonum.txt>

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VFIO Mediated devices

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:Copyright: |copy| 2016, NVIDIA CORPORATION. All rights reserved.

:Author: Neo Jia <cjia@nvidia.com>

:Author: Kirti Wankhede <kwankhede@nvidia.com>

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This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License version 2 as

published by the Free Software Foundation.

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Virtual Function I/O (VFIO) Mediated devices[1]

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The number of use cases for virtualizing DMA devices that do not have built-in

SR_IOV capability is increasing. Previously, to virtualize such devices,

developers had to create their own management interfaces and APIs, and then

integrate them with user space software. To simplify integration with user space

software, we have identified common requirements and a unified management

interface for such devices.

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The VFIO driver framework provides unified APIs for direct device access. It is

an IOMMU/device-agnostic framework for exposing direct device access to user

space in a secure, IOMMU-protected environment. This framework is used for

multiple devices, such as GPUs, network adapters, and compute accelerators. With

direct device access, virtual machines or user space applications have direct

access to the physical device. This framework is reused for mediated devices.

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The mediated core driver provides a common interface for mediated device

management that can be used by drivers of different devices. This module

provides a generic interface to perform these operations:

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* Create and destroy a mediated device

* Add a mediated device to and remove it from a mediated bus driver

* Add a mediated device to and remove it from an IOMMU group

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The mediated core driver also provides an interface to register a bus driver.

For example, the mediated VFIO mdev driver is designed for mediated devices and

supports VFIO APIs. The mediated bus driver adds a mediated device to and

removes it from a VFIO group.

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The following high-level block diagram shows the main components and interfaces

in the VFIO mediated driver framework. The diagram shows NVIDIA, Intel, and IBM

devices as examples, as these devices are the first devices to use this module::

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     +---------------+

     |               |

     | +-----------+ |  mdev_register_driver() +--------------+

     | |           | +<------------------------+              |

     | |  mdev     | |                         |              |

     | |  bus      | +------------------------>+ vfio_mdev.ko |<-> VFIO user

     | |  driver   | |     probe()/remove()    |              |    APIs

     | |           | |                         +--------------+

     | +-----------+ |

     |               |

     |  MDEV CORE    |

     |   MODULE      |

     |   mdev.ko     |

     | +-----------+ |  mdev_register_device() +--------------+