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+===================
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+Vhost-user Protocol
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+===================
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+:Copyright: 2014 Virtual Open Systems Sarl.
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+:Licence: This work is licensed under the terms of the GNU GPL,
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+ version 2 or later. See the COPYING file in the top-level
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+ directory.
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+
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+.. contents:: Table of Contents
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+
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+Introduction
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+============
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+
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+This protocol is aiming to complement the ``ioctl`` interface used to
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+control the vhost implementation in the Linux kernel. It implements
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+the control plane needed to establish virtqueue sharing with a user
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+space process on the same host. It uses communication over a Unix
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+domain socket to share file descriptors in the ancillary data of the
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+message.
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+
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+The protocol defines 2 sides of the communication, *master* and
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+*slave*. *Master* is the application that shares its virtqueues, in
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+our case QEMU. *Slave* is the consumer of the virtqueues.
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+
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+In the current implementation QEMU is the *master*, and the *slave* is
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+the external process consuming the virtio queues, for example a
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+software Ethernet switch running in user space, such as Snabbswitch,
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+or a block device backend processing read & write to a virtual
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+disk. In order to facilitate interoperability between various backend
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+implementations, it is recommended to follow the :ref:`Backend program
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+conventions <backend_conventions>`.
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+
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+*Master* and *slave* can be either a client (i.e. connecting) or
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+server (listening) in the socket communication.
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+
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+Message Specification
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+=====================
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+
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+.. Note:: All numbers are in the machine native byte order.
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+
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+A vhost-user message consists of 3 header fields and a payload.
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+
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++---------+-------+------+---------+
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+| request | flags | size | payload |
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++---------+-------+------+---------+
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+
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+Header
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+------
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+
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+:request: 32-bit type of the request
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+
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+:flags: 32-bit bit field
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+
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+- Lower 2 bits are the version (currently 0x01)
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+- Bit 2 is the reply flag - needs to be sent on each reply from the slave
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+- Bit 3 is the need_reply flag - see :ref:`REPLY_ACK <reply_ack>` for
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+ details.
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+
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+:size: 32-bit size of the payload
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+
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+Payload
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+-------
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+
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+Depending on the request type, **payload** can be:
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+
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+A single 64-bit integer
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+^^^^^^^^^^^^^^^^^^^^^^^
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+
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++-----+
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+| u64 |
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++-----+
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+
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+:u64: a 64-bit unsigned integer
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+
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+A vring state description
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+^^^^^^^^^^^^^^^^^^^^^^^^^
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+
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++-------+-----+
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+| index | num |
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++-------+-----+
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+
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+:index: a 32-bit index
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+
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+:num: a 32-bit number
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+
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+A vring address description
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+^^^^^^^^^^^^^^^^^^^^^^^^^^^
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+
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++-------+-------+------+------------+------+-----------+-----+
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+| index | flags | size | descriptor | used | available | log |
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++-------+-------+------+------------+------+-----------+-----+
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+
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+:index: a 32-bit vring index
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+
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+:flags: a 32-bit vring flags
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+
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+:descriptor: a 64-bit ring address of the vring descriptor table
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+
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+:used: a 64-bit ring address of the vring used ring
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+
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+:available: a 64-bit ring address of the vring available ring
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+
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+:log: a 64-bit guest address for logging
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+
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+Note that a ring address is an IOVA if ``VIRTIO_F_IOMMU_PLATFORM`` has
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+been negotiated. Otherwise it is a user address.
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+
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+Memory regions description
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+^^^^^^^^^^^^^^^^^^^^^^^^^^
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+
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++-------------+---------+---------+-----+---------+
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+| num regions | padding | region0 | ... | region7 |
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++-------------+---------+---------+-----+---------+
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+
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+:num regions: a 32-bit number of regions
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+
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+:padding: 32-bit
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+
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+A region is:
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+
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++---------------+------+--------------+-------------+
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+| guest address | size | user address | mmap offset |
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++---------------+------+--------------+-------------+
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+
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+:guest address: a 64-bit guest address of the region
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+
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+:size: a 64-bit size
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+
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+:user address: a 64-bit user address
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+
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+:mmap offset: 64-bit offset where region starts in the mapped memory
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+
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+Log description
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+^^^^^^^^^^^^^^^
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+
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++----------+------------+
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+| log size | log offset |
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++----------+------------+
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+
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+:log size: size of area used for logging
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+
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+:log offset: offset from start of supplied file descriptor where
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+ logging starts (i.e. where guest address 0 would be
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+ logged)
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+
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+An IOTLB message
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+^^^^^^^^^^^^^^^^
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+
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++------+------+--------------+-------------------+------+
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+| iova | size | user address | permissions flags | type |
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++------+------+--------------+-------------------+------+
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+
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+:iova: a 64-bit I/O virtual address programmed by the guest
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+
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+:size: a 64-bit size
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+
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+:user address: a 64-bit user address
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+
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+:permissions flags: an 8-bit value:
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+ - 0: No access
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+ - 1: Read access
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+ - 2: Write access
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+ - 3: Read/Write access
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+
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+:type: an 8-bit IOTLB message type:
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+ - 1: IOTLB miss
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+ - 2: IOTLB update
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+ - 3: IOTLB invalidate
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+ - 4: IOTLB access fail
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+
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+Virtio device config space
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+^^^^^^^^^^^^^^^^^^^^^^^^^^
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+
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++--------+------+-------+---------+
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+| offset | size | flags | payload |
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++--------+------+-------+---------+
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+
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+:offset: a 32-bit offset of virtio device's configuration space
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+
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+:size: a 32-bit configuration space access size in bytes
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+
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+:flags: a 32-bit value:
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+ - 0: Vhost master messages used for writeable fields
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+ - 1: Vhost master messages used for live migration
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+
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+:payload: Size bytes array holding the contents of the virtio
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+ device's configuration space
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+
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+Vring area description
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+^^^^^^^^^^^^^^^^^^^^^^
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+
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++-----+------+--------+
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+| u64 | size | offset |
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++-----+------+--------+
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+
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+:u64: a 64-bit integer contains vring index and flags
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+
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+:size: a 64-bit size of this area
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+
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+:offset: a 64-bit offset of this area from the start of the
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+ supplied file descriptor
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+
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+Inflight description
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+^^^^^^^^^^^^^^^^^^^^
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+
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++-----------+-------------+------------+------------+
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+| mmap size | mmap offset | num queues | queue size |
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++-----------+-------------+------------+------------+
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+
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+:mmap size: a 64-bit size of area to track inflight I/O
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+
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+:mmap offset: a 64-bit offset of this area from the start
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+ of the supplied file descriptor
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+
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+:num queues: a 16-bit number of virtqueues
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+
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+:queue size: a 16-bit size of virtqueues
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+
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+C structure
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+-----------
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+
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+In QEMU the vhost-user message is implemented with the following struct:
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+
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+.. code:: c
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+
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+ typedef struct VhostUserMsg {
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+ VhostUserRequest request;
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+ uint32_t flags;
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+ uint32_t size;
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+ union {
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+ uint64_t u64;
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+ struct vhost_vring_state state;
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+ struct vhost_vring_addr addr;
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+ VhostUserMemory memory;
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+ VhostUserLog log;
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+ struct vhost_iotlb_msg iotlb;
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+ VhostUserConfig config;
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+ VhostUserVringArea area;
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+ VhostUserInflight inflight;
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+ };
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+ } QEMU_PACKED VhostUserMsg;
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+
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+Communication
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+=============
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+
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+The protocol for vhost-user is based on the existing implementation of
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+vhost for the Linux Kernel. Most messages that can be sent via the
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+Unix domain socket implementing vhost-user have an equivalent ioctl to
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+the kernel implementation.
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+
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+The communication consists of *master* sending message requests and
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+*slave* sending message replies. Most of the requests don't require
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+replies. Here is a list of the ones that do:
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+
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+* ``VHOST_USER_GET_FEATURES``
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+* ``VHOST_USER_GET_PROTOCOL_FEATURES``
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+* ``VHOST_USER_GET_VRING_BASE``
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+* ``VHOST_USER_SET_LOG_BASE`` (if ``VHOST_USER_PROTOCOL_F_LOG_SHMFD``)
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+* ``VHOST_USER_GET_INFLIGHT_FD`` (if ``VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD``)
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+
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+.. seealso::
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+
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+ :ref:`REPLY_ACK <reply_ack>`
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+ The section on ``REPLY_ACK`` protocol extension.
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+
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+There are several messages that the master sends with file descriptors passed
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+in the ancillary data:
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+
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+* ``VHOST_USER_SET_MEM_TABLE``
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+* ``VHOST_USER_SET_LOG_BASE`` (if ``VHOST_USER_PROTOCOL_F_LOG_SHMFD``)
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+* ``VHOST_USER_SET_LOG_FD``
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+* ``VHOST_USER_SET_VRING_KICK``
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+* ``VHOST_USER_SET_VRING_CALL``
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+* ``VHOST_USER_SET_VRING_ERR``
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+* ``VHOST_USER_SET_SLAVE_REQ_FD``
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+* ``VHOST_USER_SET_INFLIGHT_FD`` (if ``VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD``)
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+
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+If *master* is unable to send the full message or receives a wrong
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+reply it will close the connection. An optional reconnection mechanism
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+can be implemented.
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+
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+Any protocol extensions are gated by protocol feature bits, which
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+allows full backwards compatibility on both master and slave. As
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+older slaves don't support negotiating protocol features, a feature
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+bit was dedicated for this purpose::
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+
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+ #define VHOST_USER_F_PROTOCOL_FEATURES 30
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+
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+Starting and stopping rings
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+---------------------------
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+
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+Client must only process each ring when it is started.
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+
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+Client must only pass data between the ring and the backend, when the
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+ring is enabled.
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+
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+If ring is started but disabled, client must process the ring without
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+talking to the backend.
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+
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+For example, for a networking device, in the disabled state client
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+must not supply any new RX packets, but must process and discard any
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+TX packets.
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+
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+If ``VHOST_USER_F_PROTOCOL_FEATURES`` has not been negotiated, the
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+ring is initialized in an enabled state.
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+
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+If ``VHOST_USER_F_PROTOCOL_FEATURES`` has been negotiated, the ring is
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+initialized in a disabled state. Client must not pass data to/from the
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+backend until ring is enabled by ``VHOST_USER_SET_VRING_ENABLE`` with
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+parameter 1, or after it has been disabled by
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+``VHOST_USER_SET_VRING_ENABLE`` with parameter 0.
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+
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+Each ring is initialized in a stopped state, client must not process
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+it until ring is started, or after it has been stopped.
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+
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+Client must start ring upon receiving a kick (that is, detecting that
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+file descriptor is readable) on the descriptor specified by
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+``VHOST_USER_SET_VRING_KICK``, and stop ring upon receiving
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+``VHOST_USER_GET_VRING_BASE``.
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+
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+While processing the rings (whether they are enabled or not), client
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+must support changing some configuration aspects on the fly.
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+
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+Multiple queue support
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+----------------------
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+
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+Multiple queue is treated as a protocol extension, hence the slave has
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+to implement protocol features first. The multiple queues feature is
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+supported only when the protocol feature ``VHOST_USER_PROTOCOL_F_MQ``
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+(bit 0) is set.
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+
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+The max number of queue pairs the slave supports can be queried with
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+message ``VHOST_USER_GET_QUEUE_NUM``. Master should stop when the
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+number of requested queues is bigger than that.
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+
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+As all queues share one connection, the master uses a unique index for each
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+queue in the sent message to identify a specified queue. One queue pair
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+is enabled initially. More queues are enabled dynamically, by sending
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+message ``VHOST_USER_SET_VRING_ENABLE``.
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+
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+Migration
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+---------
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+
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+During live migration, the master may need to track the modifications
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+the slave makes to the memory mapped regions. The client should mark
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+the dirty pages in a log. Once it complies to this logging, it may
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+declare the ``VHOST_F_LOG_ALL`` vhost feature.
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+
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+To start/stop logging of data/used ring writes, server may send
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+messages ``VHOST_USER_SET_FEATURES`` with ``VHOST_F_LOG_ALL`` and
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+``VHOST_USER_SET_VRING_ADDR`` with ``VHOST_VRING_F_LOG`` in ring's
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+flags set to 1/0, respectively.
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+
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+All the modifications to memory pointed by vring "descriptor" should
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+be marked. Modifications to "used" vring should be marked if
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+``VHOST_VRING_F_LOG`` is part of ring's flags.
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+
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+Dirty pages are of size::
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+
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+ #define VHOST_LOG_PAGE 0x1000
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+
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+The log memory fd is provided in the ancillary data of
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+``VHOST_USER_SET_LOG_BASE`` message when the slave has
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+``VHOST_USER_PROTOCOL_F_LOG_SHMFD`` protocol feature.
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+
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+The size of the log is supplied as part of ``VhostUserMsg`` which
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+should be large enough to cover all known guest addresses. Log starts
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+at the supplied offset in the supplied file descriptor. The log
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+covers from address 0 to the maximum of guest regions. In pseudo-code,
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+to mark page at ``addr`` as dirty::
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+
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+ page = addr / VHOST_LOG_PAGE
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+ log[page / 8] |= 1 << page % 8
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+
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+Where ``addr`` is the guest physical address.
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+
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+Use atomic operations, as the log may be concurrently manipulated.
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+
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+Note that when logging modifications to the used ring (when
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+``VHOST_VRING_F_LOG`` is set for this ring), ``log_guest_addr`` should
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+be used to calculate the log offset: the write to first byte of the
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+used ring is logged at this offset from log start. Also note that this
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+value might be outside the legal guest physical address range
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+(i.e. does not have to be covered by the ``VhostUserMemory`` table), but
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+the bit offset of the last byte of the ring must fall within the size
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+supplied by ``VhostUserLog``.
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+
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+``VHOST_USER_SET_LOG_FD`` is an optional message with an eventfd in
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+ancillary data, it may be used to inform the master that the log has
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+been modified.
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+
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+Once the source has finished migration, rings will be stopped by the
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+source. No further update must be done before rings are restarted.
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+
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+In postcopy migration the slave is started before all the memory has
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+been received from the source host, and care must be taken to avoid
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+accessing pages that have yet to be received. The slave opens a
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+'userfault'-fd and registers the memory with it; this fd is then
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+passed back over to the master. The master services requests on the
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+userfaultfd for pages that are accessed and when the page is available
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+it performs WAKE ioctl's on the userfaultfd to wake the stalled
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+slave. The client indicates support for this via the
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+``VHOST_USER_PROTOCOL_F_PAGEFAULT`` feature.
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+
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+Memory access
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+-------------
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+
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+The master sends a list of vhost memory regions to the slave using the
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+``VHOST_USER_SET_MEM_TABLE`` message. Each region has two base
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+addresses: a guest address and a user address.
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+
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+Messages contain guest addresses and/or user addresses to reference locations
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+within the shared memory. The mapping of these addresses works as follows.
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+
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|
|
+User addresses map to the vhost memory region containing that user address.
|
|
|
+
|
|
|
+When the ``VIRTIO_F_IOMMU_PLATFORM`` feature has not been negotiated:
|
|
|
+
|
|
|
+* Guest addresses map to the vhost memory region containing that guest
|
|
|
+ address.
|
|
|
+
|
|
|
+When the ``VIRTIO_F_IOMMU_PLATFORM`` feature has been negotiated:
|
|
|
+
|
|
|
+* Guest addresses are also called I/O virtual addresses (IOVAs). They are
|
|
|
+ translated to user addresses via the IOTLB.
|
|
|
+
|
|
|
+* The vhost memory region guest address is not used.
|
|
|
+
|
|
|
+IOMMU support
|
|
|
+-------------
|
|
|
+
|
|
|
+When the ``VIRTIO_F_IOMMU_PLATFORM`` feature has been negotiated, the
|
|
|
+master sends IOTLB entries update & invalidation by sending
|
|
|
+``VHOST_USER_IOTLB_MSG`` requests to the slave with a ``struct
|
|
|
+vhost_iotlb_msg`` as payload. For update events, the ``iotlb`` payload
|
|
|
+has to be filled with the update message type (2), the I/O virtual
|
|
|
+address, the size, the user virtual address, and the permissions
|
|
|
+flags. Addresses and size must be within vhost memory regions set via
|
|
|
+the ``VHOST_USER_SET_MEM_TABLE`` request. For invalidation events, the
|
|
|
+``iotlb`` payload has to be filled with the invalidation message type
|
|
|
+(3), the I/O virtual address and the size. On success, the slave is
|
|
|
+expected to reply with a zero payload, non-zero otherwise.
|
|
|
+
|
|
|
+The slave relies on the slave communcation channel (see :ref:`Slave
|
|
|
+communication <slave_communication>` section below) to send IOTLB miss
|
|
|
+and access failure events, by sending ``VHOST_USER_SLAVE_IOTLB_MSG``
|
|
|
+requests to the master with a ``struct vhost_iotlb_msg`` as
|
|
|
+payload. For miss events, the iotlb payload has to be filled with the
|
|
|
+miss message type (1), the I/O virtual address and the permissions
|
|
|
+flags. For access failure event, the iotlb payload has to be filled
|
|
|
+with the access failure message type (4), the I/O virtual address and
|
|
|
+the permissions flags. For synchronization purpose, the slave may
|
|
|
+rely on the reply-ack feature, so the master may send a reply when
|
|
|
+operation is completed if the reply-ack feature is negotiated and
|
|
|
+slaves requests a reply. For miss events, completed operation means
|
|
|
+either master sent an update message containing the IOTLB entry
|
|
|
+containing requested address and permission, or master sent nothing if
|
|
|
+the IOTLB miss message is invalid (invalid IOVA or permission).
|
|
|
+
|
|
|
+The master isn't expected to take the initiative to send IOTLB update
|
|
|
+messages, as the slave sends IOTLB miss messages for the guest virtual
|
|
|
+memory areas it needs to access.
|
|
|
+
|
|
|
+.. _slave_communication:
|
|
|
+
|
|
|
+Slave communication
|
|
|
+-------------------
|
|
|
+
|
|
|
+An optional communication channel is provided if the slave declares
|
|
|
+``VHOST_USER_PROTOCOL_F_SLAVE_REQ`` protocol feature, to allow the
|
|
|
+slave to make requests to the master.
|
|
|
+
|
|
|
+The fd is provided via ``VHOST_USER_SET_SLAVE_REQ_FD`` ancillary data.
|
|
|
+
|
|
|
+A slave may then send ``VHOST_USER_SLAVE_*`` messages to the master
|
|
|
+using this fd communication channel.
|
|
|
+
|
|
|
+If ``VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD`` protocol feature is
|
|
|
+negotiated, slave can send file descriptors (at most 8 descriptors in
|
|
|
+each message) to master via ancillary data using this fd communication
|
|
|
+channel.
|
|
|
+
|
|
|
+Inflight I/O tracking
|
|
|
+---------------------
|
|
|
+
|
|
|
+To support reconnecting after restart or crash, slave may need to
|
|
|
+resubmit inflight I/Os. If virtqueue is processed in order, we can
|
|
|
+easily achieve that by getting the inflight descriptors from
|
|
|
+descriptor table (split virtqueue) or descriptor ring (packed
|
|
|
+virtqueue). However, it can't work when we process descriptors
|
|
|
+out-of-order because some entries which store the information of
|
|
|
+inflight descriptors in available ring (split virtqueue) or descriptor
|
|
|
+ring (packed virtqueue) might be overrided by new entries. To solve
|
|
|
+this problem, slave need to allocate an extra buffer to store this
|
|
|
+information of inflight descriptors and share it with master for
|
|
|
+persistent. ``VHOST_USER_GET_INFLIGHT_FD`` and
|
|
|
+``VHOST_USER_SET_INFLIGHT_FD`` are used to transfer this buffer
|
|
|
+between master and slave. And the format of this buffer is described
|
|
|
+below:
|
|
|
+
|
|
|
++---------------+---------------+-----+---------------+
|
|
|
+| queue0 region | queue1 region | ... | queueN region |
|
|
|
++---------------+---------------+-----+---------------+
|
|
|
+
|
|
|
+N is the number of available virtqueues. Slave could get it from num
|
|
|
+queues field of ``VhostUserInflight``.
|
|
|
+
|
|
|
+For split virtqueue, queue region can be implemented as:
|
|
|
+
|
|
|
+.. code:: c
|
|
|
+
|
|
|
+ typedef struct DescStateSplit {
|
|
|
+ /* Indicate whether this descriptor is inflight or not.
|
|
|
+ * Only available for head-descriptor. */
|
|
|
+ uint8_t inflight;
|
|
|
+
|
|
|
+ /* Padding */
|
|
|
+ uint8_t padding[5];
|
|
|
+
|
|
|
+ /* Maintain a list for the last batch of used descriptors.
|
|
|
+ * Only available when batching is used for submitting */
|
|
|
+ uint16_t next;
|
|
|
+
|
|
|
+ /* Used to preserve the order of fetching available descriptors.
|
|
|
+ * Only available for head-descriptor. */
|
|
|
+ uint64_t counter;
|
|
|
+ } DescStateSplit;
|
|
|
+
|
|
|
+ typedef struct QueueRegionSplit {
|
|
|
+ /* The feature flags of this region. Now it's initialized to 0. */
|
|
|
+ uint64_t features;
|
|
|
+
|
|
|
+ /* The version of this region. It's 1 currently.
|
|
|
+ * Zero value indicates an uninitialized buffer */
|
|
|
+ uint16_t version;
|
|
|
+
|
|
|
+ /* The size of DescStateSplit array. It's equal to the virtqueue
|
|
|
+ * size. Slave could get it from queue size field of VhostUserInflight. */
|
|
|
+ uint16_t desc_num;
|
|
|
+
|
|
|
+ /* The head of list that track the last batch of used descriptors. */
|
|
|
+ uint16_t last_batch_head;
|
|
|
+
|
|
|
+ /* Store the idx value of used ring */
|
|
|
+ uint16_t used_idx;
|
|
|
+
|
|
|
+ /* Used to track the state of each descriptor in descriptor table */
|
|
|
+ DescStateSplit desc[0];
|
|
|
+ } QueueRegionSplit;
|
|
|
+
|
|
|
+To track inflight I/O, the queue region should be processed as follows:
|
|
|
+
|
|
|
+When receiving available buffers from the driver:
|
|
|
+
|
|
|
+#. Get the next available head-descriptor index from available ring, ``i``
|
|
|
+
|
|
|
+#. Set ``desc[i].counter`` to the value of global counter
|
|
|
+
|
|
|
+#. Increase global counter by 1
|
|
|
+
|
|
|
+#. Set ``desc[i].inflight`` to 1
|
|
|
+
|
|
|
+When supplying used buffers to the driver:
|
|
|
+
|
|
|
+1. Get corresponding used head-descriptor index, i
|
|
|
+
|
|
|
+2. Set ``desc[i].next`` to ``last_batch_head``
|
|
|
+
|
|
|
+3. Set ``last_batch_head`` to ``i``
|
|
|
+
|
|
|
+#. Steps 1,2,3 may be performed repeatedly if batching is possible
|
|
|
+
|
|
|
+#. Increase the ``idx`` value of used ring by the size of the batch
|
|
|
+
|
|
|
+#. Set the ``inflight`` field of each ``DescStateSplit`` entry in the batch to 0
|
|
|
+
|
|
|
+#. Set ``used_idx`` to the ``idx`` value of used ring
|
|
|
+
|
|
|
+When reconnecting:
|
|
|
+
|
|
|
+#. If the value of ``used_idx`` does not match the ``idx`` value of
|
|
|
+ used ring (means the inflight field of ``DescStateSplit`` entries in
|
|
|
+ last batch may be incorrect),
|
|
|
+
|
|
|
+ a. Subtract the value of ``used_idx`` from the ``idx`` value of
|
|
|
+ used ring to get last batch size of ``DescStateSplit`` entries
|
|
|
+
|
|
|
+ #. Set the ``inflight`` field of each ``DescStateSplit`` entry to 0 in last batch
|
|
|
+ list which starts from ``last_batch_head``
|
|
|
+
|
|
|
+ #. Set ``used_idx`` to the ``idx`` value of used ring
|
|
|
+
|
|
|
+#. Resubmit inflight ``DescStateSplit`` entries in order of their
|
|
|
+ counter value
|
|
|
+
|
|
|
+For packed virtqueue, queue region can be implemented as:
|
|
|
+
|
|
|
+.. code:: c
|
|
|
+
|
|
|
+ typedef struct DescStatePacked {
|
|
|
+ /* Indicate whether this descriptor is inflight or not.
|
|
|
+ * Only available for head-descriptor. */
|
|
|
+ uint8_t inflight;
|
|
|
+
|
|
|
+ /* Padding */
|
|
|
+ uint8_t padding;
|
|
|
+
|
|
|
+ /* Link to the next free entry */
|
|
|
+ uint16_t next;
|
|
|
+
|
|
|
+ /* Link to the last entry of descriptor list.
|
|
|
+ * Only available for head-descriptor. */
|
|
|
+ uint16_t last;
|
|
|
+
|
|
|
+ /* The length of descriptor list.
|
|
|
+ * Only available for head-descriptor. */
|
|
|
+ uint16_t num;
|
|
|
+
|
|
|
+ /* Used to preserve the order of fetching available descriptors.
|
|
|
+ * Only available for head-descriptor. */
|
|
|
+ uint64_t counter;
|
|
|
+
|
|
|
+ /* The buffer id */
|
|
|
+ uint16_t id;
|
|
|
+
|
|
|
+ /* The descriptor flags */
|
|
|
+ uint16_t flags;
|
|
|
+
|
|
|
+ /* The buffer length */
|
|
|
+ uint32_t len;
|
|
|
+
|
|
|
+ /* The buffer address */
|
|
|
+ uint64_t addr;
|
|
|
+ } DescStatePacked;
|
|
|
+
|
|
|
+ typedef struct QueueRegionPacked {
|
|
|
+ /* The feature flags of this region. Now it's initialized to 0. */
|
|
|
+ uint64_t features;
|
|
|
+
|
|
|
+ /* The version of this region. It's 1 currently.
|
|
|
+ * Zero value indicates an uninitialized buffer */
|
|
|
+ uint16_t version;
|
|
|
+
|
|
|
+ /* The size of DescStatePacked array. It's equal to the virtqueue
|
|
|
+ * size. Slave could get it from queue size field of VhostUserInflight. */
|
|
|
+ uint16_t desc_num;
|
|
|
+
|
|
|
+ /* The head of free DescStatePacked entry list */
|
|
|
+ uint16_t free_head;
|
|
|
+
|
|
|
+ /* The old head of free DescStatePacked entry list */
|
|
|
+ uint16_t old_free_head;
|
|
|
+
|
|
|
+ /* The used index of descriptor ring */
|
|
|
+ uint16_t used_idx;
|
|
|
+
|
|
|
+ /* The old used index of descriptor ring */
|
|
|
+ uint16_t old_used_idx;
|
|
|
+
|
|
|
+ /* Device ring wrap counter */
|
|
|
+ uint8_t used_wrap_counter;
|
|
|
+
|
|
|
+ /* The old device ring wrap counter */
|
|
|
+ uint8_t old_used_wrap_counter;
|
|
|
+
|
|
|
+ /* Padding */
|
|
|
+ uint8_t padding[7];
|
|
|
+
|
|
|
+ /* Used to track the state of each descriptor fetched from descriptor ring */
|
|
|
+ DescStatePacked desc[0];
|
|
|
+ } QueueRegionPacked;
|
|
|
+
|
|
|
+To track inflight I/O, the queue region should be processed as follows:
|
|
|
+
|
|
|
+When receiving available buffers from the driver:
|
|
|
+
|
|
|
+#. Get the next available descriptor entry from descriptor ring, ``d``
|
|
|
+
|
|
|
+#. If ``d`` is head descriptor,
|
|
|
+
|
|
|
+ a. Set ``desc[old_free_head].num`` to 0
|
|
|
+
|
|
|
+ #. Set ``desc[old_free_head].counter`` to the value of global counter
|
|
|
+
|
|
|
+ #. Increase global counter by 1
|
|
|
+
|
|
|
+ #. Set ``desc[old_free_head].inflight`` to 1
|
|
|
+
|
|
|
+#. If ``d`` is last descriptor, set ``desc[old_free_head].last`` to
|
|
|
+ ``free_head``
|
|
|
+
|
|
|
+#. Increase ``desc[old_free_head].num`` by 1
|
|
|
+
|
|
|
+#. Set ``desc[free_head].addr``, ``desc[free_head].len``,
|
|
|
+ ``desc[free_head].flags``, ``desc[free_head].id`` to ``d.addr``,
|
|
|
+ ``d.len``, ``d.flags``, ``d.id``
|
|
|
+
|
|
|
+#. Set ``free_head`` to ``desc[free_head].next``
|
|
|
+
|
|
|
+#. If ``d`` is last descriptor, set ``old_free_head`` to ``free_head``
|
|
|
+
|
|
|
+When supplying used buffers to the driver:
|
|
|
+
|
|
|
+1. Get corresponding used head-descriptor entry from descriptor ring,
|
|
|
+ ``d``
|
|
|
+
|
|
|
+2. Get corresponding ``DescStatePacked`` entry, ``e``
|
|
|
+
|
|
|
+3. Set ``desc[e.last].next`` to ``free_head``
|
|
|
+
|
|
|
+4. Set ``free_head`` to the index of ``e``
|
|
|
+
|
|
|
+#. Steps 1,2,3,4 may be performed repeatedly if batching is possible
|
|
|
+
|
|
|
+#. Increase ``used_idx`` by the size of the batch and update
|
|
|
+ ``used_wrap_counter`` if needed
|
|
|
+
|
|
|
+#. Update ``d.flags``
|
|
|
+
|
|
|
+#. Set the ``inflight`` field of each head ``DescStatePacked`` entry
|
|
|
+ in the batch to 0
|
|
|
+
|
|
|
+#. Set ``old_free_head``, ``old_used_idx``, ``old_used_wrap_counter``
|
|
|
+ to ``free_head``, ``used_idx``, ``used_wrap_counter``
|
|
|
+
|
|
|
+When reconnecting:
|
|
|
+
|
|
|
+#. If ``used_idx`` does not match ``old_used_idx`` (means the
|
|
|
+ ``inflight`` field of ``DescStatePacked`` entries in last batch may
|
|
|
+ be incorrect),
|
|
|
+
|
|
|
+ a. Get the next descriptor ring entry through ``old_used_idx``, ``d``
|
|
|
+
|
|
|
+ #. Use ``old_used_wrap_counter`` to calculate the available flags
|
|
|
+
|
|
|
+ #. If ``d.flags`` is not equal to the calculated flags value (means
|
|
|
+ slave has submitted the buffer to guest driver before crash, so
|
|
|
+ it has to commit the in-progres update), set ``old_free_head``,
|
|
|
+ ``old_used_idx``, ``old_used_wrap_counter`` to ``free_head``,
|
|
|
+ ``used_idx``, ``used_wrap_counter``
|
|
|
+
|
|
|
+#. Set ``free_head``, ``used_idx``, ``used_wrap_counter`` to
|
|
|
+ ``old_free_head``, ``old_used_idx``, ``old_used_wrap_counter``
|
|
|
+ (roll back any in-progress update)
|
|
|
+
|
|
|
+#. Set the ``inflight`` field of each ``DescStatePacked`` entry in
|
|
|
+ free list to 0
|
|
|
+
|
|
|
+#. Resubmit inflight ``DescStatePacked`` entries in order of their
|
|
|
+ counter value
|
|
|
+
|
|
|
+Protocol features
|
|
|
+-----------------
|
|
|
+
|
|
|
+.. code:: c
|
|
|
+
|
|
|
+ #define VHOST_USER_PROTOCOL_F_MQ 0
|
|
|
+ #define VHOST_USER_PROTOCOL_F_LOG_SHMFD 1
|
|
|
+ #define VHOST_USER_PROTOCOL_F_RARP 2
|
|
|
+ #define VHOST_USER_PROTOCOL_F_REPLY_ACK 3
|
|
|
+ #define VHOST_USER_PROTOCOL_F_MTU 4
|
|
|
+ #define VHOST_USER_PROTOCOL_F_SLAVE_REQ 5
|
|
|
+ #define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN 6
|
|
|
+ #define VHOST_USER_PROTOCOL_F_CRYPTO_SESSION 7
|
|
|
+ #define VHOST_USER_PROTOCOL_F_PAGEFAULT 8
|
|
|
+ #define VHOST_USER_PROTOCOL_F_CONFIG 9
|
|
|
+ #define VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD 10
|
|
|
+ #define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11
|
|
|
+ #define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD 12
|
|
|
+
|
|
|
+Master message types
|
|
|
+--------------------
|
|
|
+
|
|
|
+``VHOST_USER_GET_FEATURES``
|
|
|
+ :id: 1
|
|
|
+ :equivalent ioctl: ``VHOST_GET_FEATURES``
|
|
|
+ :master payload: N/A
|
|
|
+ :slave payload: ``u64``
|
|
|
+
|
|
|
+ Get from the underlying vhost implementation the features bitmask.
|
|
|
+ Feature bit ``VHOST_USER_F_PROTOCOL_FEATURES`` signals slave support
|
|
|
+ for ``VHOST_USER_GET_PROTOCOL_FEATURES`` and
|
|
|
+ ``VHOST_USER_SET_PROTOCOL_FEATURES``.
|
|
|
+
|
|
|
+``VHOST_USER_SET_FEATURES``
|
|
|
+ :id: 2
|
|
|
+ :equivalent ioctl: ``VHOST_SET_FEATURES``
|
|
|
+ :master payload: ``u64``
|
|
|
+
|
|
|
+ Enable features in the underlying vhost implementation using a
|
|
|
+ bitmask. Feature bit ``VHOST_USER_F_PROTOCOL_FEATURES`` signals
|
|
|
+ slave support for ``VHOST_USER_GET_PROTOCOL_FEATURES`` and
|
|
|
+ ``VHOST_USER_SET_PROTOCOL_FEATURES``.
|
|
|
+
|
|
|
+``VHOST_USER_GET_PROTOCOL_FEATURES``
|
|
|
+ :id: 15
|
|
|
+ :equivalent ioctl: ``VHOST_GET_FEATURES``
|
|
|
+ :master payload: N/A
|
|
|
+ :slave payload: ``u64``
|
|
|
+
|
|
|
+ Get the protocol feature bitmask from the underlying vhost
|
|
|
+ implementation. Only legal if feature bit
|
|
|
+ ``VHOST_USER_F_PROTOCOL_FEATURES`` is present in
|
|
|
+ ``VHOST_USER_GET_FEATURES``.
|
|
|
+
|
|
|
+.. Note::
|
|
|
+ Slave that reported ``VHOST_USER_F_PROTOCOL_FEATURES`` must
|
|
|
+ support this message even before ``VHOST_USER_SET_FEATURES`` was
|
|
|
+ called.
|
|
|
+
|
|
|
+``VHOST_USER_SET_PROTOCOL_FEATURES``
|
|
|
+ :id: 16
|
|
|
+ :equivalent ioctl: ``VHOST_SET_FEATURES``
|
|
|
+ :master payload: ``u64``
|
|
|
+
|
|
|
+ Enable protocol features in the underlying vhost implementation.
|
|
|
+
|
|
|
+ Only legal if feature bit ``VHOST_USER_F_PROTOCOL_FEATURES`` is present in
|
|
|
+ ``VHOST_USER_GET_FEATURES``.
|
|
|
+
|
|
|
+.. Note::
|
|
|
+ Slave that reported ``VHOST_USER_F_PROTOCOL_FEATURES`` must support
|
|
|
+ this message even before ``VHOST_USER_SET_FEATURES`` was called.
|
|
|
+
|
|
|
+``VHOST_USER_SET_OWNER``
|
|
|
+ :id: 3
|
|
|
+ :equivalent ioctl: ``VHOST_SET_OWNER``
|
|
|
+ :master payload: N/A
|
|
|
+
|
|
|
+ Issued when a new connection is established. It sets the current
|
|
|
+ *master* as an owner of the session. This can be used on the *slave*
|
|
|
+ as a "session start" flag.
|
|
|
+
|
|
|
+``VHOST_USER_RESET_OWNER``
|
|
|
+ :id: 4
|
|
|
+ :master payload: N/A
|
|
|
+
|
|
|
+.. admonition:: Deprecated
|
|
|
+
|
|
|
+ This is no longer used. Used to be sent to request disabling all
|
|
|
+ rings, but some clients interpreted it to also discard connection
|
|
|
+ state (this interpretation would lead to bugs). It is recommended
|
|
|
+ that clients either ignore this message, or use it to disable all
|
|
|
+ rings.
|
|
|
+
|
|
|
+``VHOST_USER_SET_MEM_TABLE``
|
|
|
+ :id: 5
|
|
|
+ :equivalent ioctl: ``VHOST_SET_MEM_TABLE``
|
|
|
+ :master payload: memory regions description
|
|
|
+ :slave payload: (postcopy only) memory regions description
|
|
|
+
|
|
|
+ Sets the memory map regions on the slave so it can translate the
|
|
|
+ vring addresses. In the ancillary data there is an array of file
|
|
|
+ descriptors for each memory mapped region. The size and ordering of
|
|
|
+ the fds matches the number and ordering of memory regions.
|
|
|
+
|
|
|
+ When ``VHOST_USER_POSTCOPY_LISTEN`` has been received,
|
|
|
+ ``SET_MEM_TABLE`` replies with the bases of the memory mapped
|
|
|
+ regions to the master. The slave must have mmap'd the regions but
|
|
|
+ not yet accessed them and should not yet generate a userfault
|
|
|
+ event.
|
|
|
+
|
|
|
+.. Note::
|
|
|
+ ``NEED_REPLY_MASK`` is not set in this case. QEMU will then
|
|
|
+ reply back to the list of mappings with an empty
|
|
|
+ ``VHOST_USER_SET_MEM_TABLE`` as an acknowledgement; only upon
|
|
|
+ reception of this message may the guest start accessing the memory
|
|
|
+ and generating faults.
|
|
|
+
|
|
|
+``VHOST_USER_SET_LOG_BASE``
|
|
|
+ :id: 6
|
|
|
+ :equivalent ioctl: ``VHOST_SET_LOG_BASE``
|
|
|
+ :master payload: u64
|
|
|
+ :slave payload: N/A
|
|
|
+
|
|
|
+ Sets logging shared memory space.
|
|
|
+
|
|
|
+ When slave has ``VHOST_USER_PROTOCOL_F_LOG_SHMFD`` protocol feature,
|
|
|
+ the log memory fd is provided in the ancillary data of
|
|
|
+ ``VHOST_USER_SET_LOG_BASE`` message, the size and offset of shared
|
|
|
+ memory area provided in the message.
|
|
|
+
|
|
|
+``VHOST_USER_SET_LOG_FD``
|
|
|
+ :id: 7
|
|
|
+ :equivalent ioctl: ``VHOST_SET_LOG_FD``
|
|
|
+ :master payload: N/A
|
|
|
+
|
|
|
+ Sets the logging file descriptor, which is passed as ancillary data.
|
|
|
+
|
|
|
+``VHOST_USER_SET_VRING_NUM``
|
|
|
+ :id: 8
|
|
|
+ :equivalent ioctl: ``VHOST_SET_VRING_NUM``
|
|
|
+ :master payload: vring state description
|
|
|
+
|
|
|
+ Set the size of the queue.
|
|
|
+
|
|
|
+``VHOST_USER_SET_VRING_ADDR``
|
|
|
+ :id: 9
|
|
|
+ :equivalent ioctl: ``VHOST_SET_VRING_ADDR``
|
|
|
+ :master payload: vring address description
|
|
|
+ :slave payload: N/A
|
|
|
+
|
|
|
+ Sets the addresses of the different aspects of the vring.
|
|
|
+
|
|
|
+``VHOST_USER_SET_VRING_BASE``
|
|
|
+ :id: 10
|
|
|
+ :equivalent ioctl: ``VHOST_SET_VRING_BASE``
|
|
|
+ :master payload: vring state description
|
|
|
+
|
|
|
+ Sets the base offset in the available vring.
|
|
|
+
|
|
|
+``VHOST_USER_GET_VRING_BASE``
|
|
|
+ :id: 11
|
|
|
+ :equivalent ioctl: ``VHOST_USER_GET_VRING_BASE``
|
|
|
+ :master payload: vring state description
|
|
|
+ :slave payload: vring state description
|
|
|
+
|
|
|
+ Get the available vring base offset.
|
|
|
+
|
|
|
+``VHOST_USER_SET_VRING_KICK``
|
|
|
+ :id: 12
|
|
|
+ :equivalent ioctl: ``VHOST_SET_VRING_KICK``
|
|
|
+ :master payload: ``u64``
|
|
|
+
|
|
|
+ Set the event file descriptor for adding buffers to the vring. It is
|
|
|
+ passed in the ancillary data.
|
|
|
+
|
|
|
+ Bits (0-7) of the payload contain the vring index. Bit 8 is the
|
|
|
+ invalid FD flag. This flag is set when there is no file descriptor
|
|
|
+ in the ancillary data. This signals that polling should be used
|
|
|
+ instead of waiting for a kick.
|
|
|
+
|
|
|
+``VHOST_USER_SET_VRING_CALL``
|
|
|
+ :id: 13
|
|
|
+ :equivalent ioctl: ``VHOST_SET_VRING_CALL``
|
|
|
+ :master payload: ``u64``
|
|
|
+
|
|
|
+ Set the event file descriptor to signal when buffers are used. It is
|
|
|
+ passed in the ancillary data.
|
|
|
+
|
|
|
+ Bits (0-7) of the payload contain the vring index. Bit 8 is the
|
|
|
+ invalid FD flag. This flag is set when there is no file descriptor
|
|
|
+ in the ancillary data. This signals that polling will be used
|
|
|
+ instead of waiting for the call.
|
|
|
+
|
|
|
+``VHOST_USER_SET_VRING_ERR``
|
|
|
+ :id: 14
|
|
|
+ :equivalent ioctl: ``VHOST_SET_VRING_ERR``
|
|
|
+ :master payload: ``u64``
|
|
|
+
|
|
|
+ Set the event file descriptor to signal when error occurs. It is
|
|
|
+ passed in the ancillary data.
|
|
|
+
|
|
|
+ Bits (0-7) of the payload contain the vring index. Bit 8 is the
|
|
|
+ invalid FD flag. This flag is set when there is no file descriptor
|
|
|
+ in the ancillary data.
|
|
|
+
|
|
|
+``VHOST_USER_GET_QUEUE_NUM``
|
|
|
+ :id: 17
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :master payload: N/A
|
|
|
+ :slave payload: u64
|
|
|
+
|
|
|
+ Query how many queues the backend supports.
|
|
|
+
|
|
|
+ This request should be sent only when ``VHOST_USER_PROTOCOL_F_MQ``
|
|
|
+ is set in queried protocol features by
|
|
|
+ ``VHOST_USER_GET_PROTOCOL_FEATURES``.
|
|
|
+
|
|
|
+``VHOST_USER_SET_VRING_ENABLE``
|
|
|
+ :id: 18
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :master payload: vring state description
|
|
|
+
|
|
|
+ Signal slave to enable or disable corresponding vring.
|
|
|
+
|
|
|
+ This request should be sent only when
|
|
|
+ ``VHOST_USER_F_PROTOCOL_FEATURES`` has been negotiated.
|
|
|
+
|
|
|
+``VHOST_USER_SEND_RARP``
|
|
|
+ :id: 19
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :master payload: ``u64``
|
|
|
+
|
|
|
+ Ask vhost user backend to broadcast a fake RARP to notify the migration
|
|
|
+ is terminated for guest that does not support GUEST_ANNOUNCE.
|
|
|
+
|
|
|
+ Only legal if feature bit ``VHOST_USER_F_PROTOCOL_FEATURES`` is
|
|
|
+ present in ``VHOST_USER_GET_FEATURES`` and protocol feature bit
|
|
|
+ ``VHOST_USER_PROTOCOL_F_RARP`` is present in
|
|
|
+ ``VHOST_USER_GET_PROTOCOL_FEATURES``. The first 6 bytes of the
|
|
|
+ payload contain the mac address of the guest to allow the vhost user
|
|
|
+ backend to construct and broadcast the fake RARP.
|
|
|
+
|
|
|
+``VHOST_USER_NET_SET_MTU``
|
|
|
+ :id: 20
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :master payload: ``u64``
|
|
|
+
|
|
|
+ Set host MTU value exposed to the guest.
|
|
|
+
|
|
|
+ This request should be sent only when ``VIRTIO_NET_F_MTU`` feature
|
|
|
+ has been successfully negotiated, ``VHOST_USER_F_PROTOCOL_FEATURES``
|
|
|
+ is present in ``VHOST_USER_GET_FEATURES`` and protocol feature bit
|
|
|
+ ``VHOST_USER_PROTOCOL_F_NET_MTU`` is present in
|
|
|
+ ``VHOST_USER_GET_PROTOCOL_FEATURES``.
|
|
|
+
|
|
|
+ If ``VHOST_USER_PROTOCOL_F_REPLY_ACK`` is negotiated, slave must
|
|
|
+ respond with zero in case the specified MTU is valid, or non-zero
|
|
|
+ otherwise.
|
|
|
+
|
|
|
+``VHOST_USER_SET_SLAVE_REQ_FD``
|
|
|
+ :id: 21
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :master payload: N/A
|
|
|
+
|
|
|
+ Set the socket file descriptor for slave initiated requests. It is passed
|
|
|
+ in the ancillary data.
|
|
|
+
|
|
|
+ This request should be sent only when
|
|
|
+ ``VHOST_USER_F_PROTOCOL_FEATURES`` has been negotiated, and protocol
|
|
|
+ feature bit ``VHOST_USER_PROTOCOL_F_SLAVE_REQ`` bit is present in
|
|
|
+ ``VHOST_USER_GET_PROTOCOL_FEATURES``. If
|
|
|
+ ``VHOST_USER_PROTOCOL_F_REPLY_ACK`` is negotiated, slave must
|
|
|
+ respond with zero for success, non-zero otherwise.
|
|
|
+
|
|
|
+``VHOST_USER_IOTLB_MSG``
|
|
|
+ :id: 22
|
|
|
+ :equivalent ioctl: N/A (equivalent to ``VHOST_IOTLB_MSG`` message type)
|
|
|
+ :master payload: ``struct vhost_iotlb_msg``
|
|
|
+ :slave payload: ``u64``
|
|
|
+
|
|
|
+ Send IOTLB messages with ``struct vhost_iotlb_msg`` as payload.
|
|
|
+
|
|
|
+ Master sends such requests to update and invalidate entries in the
|
|
|
+ device IOTLB. The slave has to acknowledge the request with sending
|
|
|
+ zero as ``u64`` payload for success, non-zero otherwise.
|
|
|
+
|
|
|
+ This request should be send only when ``VIRTIO_F_IOMMU_PLATFORM``
|
|
|
+ feature has been successfully negotiated.
|
|
|
+
|
|
|
+``VHOST_USER_SET_VRING_ENDIAN``
|
|
|
+ :id: 23
|
|
|
+ :equivalent ioctl: ``VHOST_SET_VRING_ENDIAN``
|
|
|
+ :master payload: vring state description
|
|
|
+
|
|
|
+ Set the endianness of a VQ for legacy devices. Little-endian is
|
|
|
+ indicated with state.num set to 0 and big-endian is indicated with
|
|
|
+ state.num set to 1. Other values are invalid.
|
|
|
+
|
|
|
+ This request should be sent only when
|
|
|
+ ``VHOST_USER_PROTOCOL_F_CROSS_ENDIAN`` has been negotiated.
|
|
|
+ Backends that negotiated this feature should handle both
|
|
|
+ endiannesses and expect this message once (per VQ) during device
|
|
|
+ configuration (ie. before the master starts the VQ).
|
|
|
+
|
|
|
+``VHOST_USER_GET_CONFIG``
|
|
|
+ :id: 24
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :master payload: virtio device config space
|
|
|
+ :slave payload: virtio device config space
|
|
|
+
|
|
|
+ When ``VHOST_USER_PROTOCOL_F_CONFIG`` is negotiated, this message is
|
|
|
+ submitted by the vhost-user master to fetch the contents of the
|
|
|
+ virtio device configuration space, vhost-user slave's payload size
|
|
|
+ MUST match master's request, vhost-user slave uses zero length of
|
|
|
+ payload to indicate an error to vhost-user master. The vhost-user
|
|
|
+ master may cache the contents to avoid repeated
|
|
|
+ ``VHOST_USER_GET_CONFIG`` calls.
|
|
|
+
|
|
|
+``VHOST_USER_SET_CONFIG``
|
|
|
+ :id: 25
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :master payload: virtio device config space
|
|
|
+ :slave payload: N/A
|
|
|
+
|
|
|
+ When ``VHOST_USER_PROTOCOL_F_CONFIG`` is negotiated, this message is
|
|
|
+ submitted by the vhost-user master when the Guest changes the virtio
|
|
|
+ device configuration space and also can be used for live migration
|
|
|
+ on the destination host. The vhost-user slave must check the flags
|
|
|
+ field, and slaves MUST NOT accept SET_CONFIG for read-only
|
|
|
+ configuration space fields unless the live migration bit is set.
|
|
|
+
|
|
|
+``VHOST_USER_CREATE_CRYPTO_SESSION``
|
|
|
+ :id: 26
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :master payload: crypto session description
|
|
|
+ :slave payload: crypto session description
|
|
|
+
|
|
|
+ Create a session for crypto operation. The server side must return
|
|
|
+ the session id, 0 or positive for success, negative for failure.
|
|
|
+ This request should be sent only when
|
|
|
+ ``VHOST_USER_PROTOCOL_F_CRYPTO_SESSION`` feature has been
|
|
|
+ successfully negotiated. It's a required feature for crypto
|
|
|
+ devices.
|
|
|
+
|
|
|
+``VHOST_USER_CLOSE_CRYPTO_SESSION``
|
|
|
+ :id: 27
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :master payload: ``u64``
|
|
|
+
|
|
|
+ Close a session for crypto operation which was previously
|
|
|
+ created by ``VHOST_USER_CREATE_CRYPTO_SESSION``.
|
|
|
+
|
|
|
+ This request should be sent only when
|
|
|
+ ``VHOST_USER_PROTOCOL_F_CRYPTO_SESSION`` feature has been
|
|
|
+ successfully negotiated. It's a required feature for crypto
|
|
|
+ devices.
|
|
|
+
|
|
|
+``VHOST_USER_POSTCOPY_ADVISE``
|
|
|
+ :id: 28
|
|
|
+ :master payload: N/A
|
|
|
+ :slave payload: userfault fd
|
|
|
+
|
|
|
+ When ``VHOST_USER_PROTOCOL_F_PAGEFAULT`` is supported, the master
|
|
|
+ advises slave that a migration with postcopy enabled is underway,
|
|
|
+ the slave must open a userfaultfd for later use. Note that at this
|
|
|
+ stage the migration is still in precopy mode.
|
|
|
+
|
|
|
+``VHOST_USER_POSTCOPY_LISTEN``
|
|
|
+ :id: 29
|
|
|
+ :master payload: N/A
|
|
|
+
|
|
|
+ Master advises slave that a transition to postcopy mode has
|
|
|
+ happened. The slave must ensure that shared memory is registered
|
|
|
+ with userfaultfd to cause faulting of non-present pages.
|
|
|
+
|
|
|
+ This is always sent sometime after a ``VHOST_USER_POSTCOPY_ADVISE``,
|
|
|
+ and thus only when ``VHOST_USER_PROTOCOL_F_PAGEFAULT`` is supported.
|
|
|
+
|
|
|
+``VHOST_USER_POSTCOPY_END``
|
|
|
+ :id: 30
|
|
|
+ :slave payload: ``u64``
|
|
|
+
|
|
|
+ Master advises that postcopy migration has now completed. The slave
|
|
|
+ must disable the userfaultfd. The response is an acknowledgement
|
|
|
+ only.
|
|
|
+
|
|
|
+ When ``VHOST_USER_PROTOCOL_F_PAGEFAULT`` is supported, this message
|
|
|
+ is sent at the end of the migration, after
|
|
|
+ ``VHOST_USER_POSTCOPY_LISTEN`` was previously sent.
|
|
|
+
|
|
|
+ The value returned is an error indication; 0 is success.
|
|
|
+
|
|
|
+``VHOST_USER_GET_INFLIGHT_FD``
|
|
|
+ :id: 31
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :master payload: inflight description
|
|
|
+
|
|
|
+ When ``VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD`` protocol feature has
|
|
|
+ been successfully negotiated, this message is submitted by master to
|
|
|
+ get a shared buffer from slave. The shared buffer will be used to
|
|
|
+ track inflight I/O by slave. QEMU should retrieve a new one when vm
|
|
|
+ reset.
|
|
|
+
|
|
|
+``VHOST_USER_SET_INFLIGHT_FD``
|
|
|
+ :id: 32
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :master payload: inflight description
|
|
|
+
|
|
|
+ When ``VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD`` protocol feature has
|
|
|
+ been successfully negotiated, this message is submitted by master to
|
|
|
+ send the shared inflight buffer back to slave so that slave could
|
|
|
+ get inflight I/O after a crash or restart.
|
|
|
+
|
|
|
+Slave message types
|
|
|
+-------------------
|
|
|
+
|
|
|
+``VHOST_USER_SLAVE_IOTLB_MSG``
|
|
|
+ :id: 1
|
|
|
+ :equivalent ioctl: N/A (equivalent to ``VHOST_IOTLB_MSG`` message type)
|
|
|
+ :slave payload: ``struct vhost_iotlb_msg``
|
|
|
+ :master payload: N/A
|
|
|
+
|
|
|
+ Send IOTLB messages with ``struct vhost_iotlb_msg`` as payload.
|
|
|
+ Slave sends such requests to notify of an IOTLB miss, or an IOTLB
|
|
|
+ access failure. If ``VHOST_USER_PROTOCOL_F_REPLY_ACK`` is
|
|
|
+ negotiated, and slave set the ``VHOST_USER_NEED_REPLY`` flag, master
|
|
|
+ must respond with zero when operation is successfully completed, or
|
|
|
+ non-zero otherwise. This request should be send only when
|
|
|
+ ``VIRTIO_F_IOMMU_PLATFORM`` feature has been successfully
|
|
|
+ negotiated.
|
|
|
+
|
|
|
+``VHOST_USER_SLAVE_CONFIG_CHANGE_MSG``
|
|
|
+ :id: 2
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :slave payload: N/A
|
|
|
+ :master payload: N/A
|
|
|
+
|
|
|
+ When ``VHOST_USER_PROTOCOL_F_CONFIG`` is negotiated, vhost-user
|
|
|
+ slave sends such messages to notify that the virtio device's
|
|
|
+ configuration space has changed, for those host devices which can
|
|
|
+ support such feature, host driver can send ``VHOST_USER_GET_CONFIG``
|
|
|
+ message to slave to get the latest content. If
|
|
|
+ ``VHOST_USER_PROTOCOL_F_REPLY_ACK`` is negotiated, and slave set the
|
|
|
+ ``VHOST_USER_NEED_REPLY`` flag, master must respond with zero when
|
|
|
+ operation is successfully completed, or non-zero otherwise.
|
|
|
+
|
|
|
+``VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG``
|
|
|
+ :id: 3
|
|
|
+ :equivalent ioctl: N/A
|
|
|
+ :slave payload: vring area description
|
|
|
+ :master payload: N/A
|
|
|
+
|
|
|
+ Sets host notifier for a specified queue. The queue index is
|
|
|
+ contained in the ``u64`` field of the vring area description. The
|
|
|
+ host notifier is described by the file descriptor (typically it's a
|
|
|
+ VFIO device fd) which is passed as ancillary data and the size
|
|
|
+ (which is mmap size and should be the same as host page size) and
|
|
|
+ offset (which is mmap offset) carried in the vring area
|
|
|
+ description. QEMU can mmap the file descriptor based on the size and
|
|
|
+ offset to get a memory range. Registering a host notifier means
|
|
|
+ mapping this memory range to the VM as the specified queue's notify
|
|
|
+ MMIO region. Slave sends this request to tell QEMU to de-register
|
|
|
+ the existing notifier if any and register the new notifier if the
|
|
|
+ request is sent with a file descriptor.
|
|
|
+
|
|
|
+ This request should be sent only when
|
|
|
+ ``VHOST_USER_PROTOCOL_F_HOST_NOTIFIER`` protocol feature has been
|
|
|
+ successfully negotiated.
|
|
|
+
|
|
|
+.. _reply_ack:
|
|
|
+
|
|
|
+VHOST_USER_PROTOCOL_F_REPLY_ACK
|
|
|
+-------------------------------
|
|
|
+
|
|
|
+The original vhost-user specification only demands replies for certain
|
|
|
+commands. This differs from the vhost protocol implementation where
|
|
|
+commands are sent over an ``ioctl()`` call and block until the client
|
|
|
+has completed.
|
|
|
+
|
|
|
+With this protocol extension negotiated, the sender (QEMU) can set the
|
|
|
+``need_reply`` [Bit 3] flag to any command. This indicates that the
|
|
|
+client MUST respond with a Payload ``VhostUserMsg`` indicating success
|
|
|
+or failure. The payload should be set to zero on success or non-zero
|
|
|
+on failure, unless the message already has an explicit reply body.
|
|
|
+
|
|
|
+The response payload gives QEMU a deterministic indication of the result
|
|
|
+of the command. Today, QEMU is expected to terminate the main vhost-user
|
|
|
+loop upon receiving such errors. In future, qemu could be taught to be more
|
|
|
+resilient for selective requests.
|
|
|
+
|
|
|
+For the message types that already solicit a reply from the client,
|
|
|
+the presence of ``VHOST_USER_PROTOCOL_F_REPLY_ACK`` or need_reply bit
|
|
|
+being set brings no behavioural change. (See the Communication_
|
|
|
+section for details.)
|
|
|
+
|
|
|
+.. _backend_conventions:
|
|
|
+
|
|
|
+Backend program conventions
|
|
|
+===========================
|
|
|
+
|
|
|
+vhost-user backends can provide various devices & services and may
|
|
|
+need to be configured manually depending on the use case. However, it
|
|
|
+is a good idea to follow the conventions listed here when
|
|
|
+possible. Users, QEMU or libvirt, can then rely on some common
|
|
|
+behaviour to avoid heterogenous configuration and management of the
|
|
|
+backend programs and facilitate interoperability.
|
|
|
+
|
|
|
+Each backend installed on a host system should come with at least one
|
|
|
+JSON file that conforms to the vhost-user.json schema. Each file
|
|
|
+informs the management applications about the backend type, and binary
|
|
|
+location. In addition, it defines rules for management apps for
|
|
|
+picking the highest priority backend when multiple match the search
|
|
|
+criteria (see ``@VhostUserBackend`` documentation in the schema file).
|
|
|
+
|
|
|
+If the backend is not capable of enabling a requested feature on the
|
|
|
+host (such as 3D acceleration with virgl), or the initialization
|
|
|
+failed, the backend should fail to start early and exit with a status
|
|
|
+!= 0. It may also print a message to stderr for further details.
|
|
|
+
|
|
|
+The backend program must not daemonize itself, but it may be
|
|
|
+daemonized by the management layer. It may also have a restricted
|
|
|
+access to the system.
|
|
|
+
|
|
|
+File descriptors 0, 1 and 2 will exist, and have regular
|
|
|
+stdin/stdout/stderr usage (they may have been redirected to /dev/null
|
|
|
+by the management layer, or to a log handler).
|
|
|
+
|
|
|
+The backend program must end (as quickly and cleanly as possible) when
|
|
|
+the SIGTERM signal is received. Eventually, it may receive SIGKILL by
|
|
|
+the management layer after a few seconds.
|
|
|
+
|
|
|
+The following command line options have an expected behaviour. They
|
|
|
+are mandatory, unless explicitly said differently:
|
|
|
+
|
|
|
+--socket-path=PATH
|
|
|
+
|
|
|
+ This option specify the location of the vhost-user Unix domain socket.
|
|
|
+ It is incompatible with --fd.
|
|
|
+
|
|
|
+--fd=FDNUM
|
|
|
+
|
|
|
+ When this argument is given, the backend program is started with the
|
|
|
+ vhost-user socket as file descriptor FDNUM. It is incompatible with
|
|
|
+ --socket-path.
|
|
|
+
|
|
|
+--print-capabilities
|
|
|
+
|
|
|
+ Output to stdout the backend capabilities in JSON format, and then
|
|
|
+ exit successfully. Other options and arguments should be ignored, and
|
|
|
+ the backend program should not perform its normal function. The
|
|
|
+ capabilities can be reported dynamically depending on the host
|
|
|
+ capabilities.
|
|
|
+
|
|
|
+The JSON output is described in the ``vhost-user.json`` schema, by
|
|
|
+```@VHostUserBackendCapabilities``. Example:
|
|
|
+
|
|
|
+.. code:: json
|
|
|
+
|
|
|
+ {
|
|
|
+ "type": "foo",
|
|
|
+ "features": [
|
|
|
+ "feature-a",
|
|
|
+ "feature-b"
|
|
|
+ ]
|
|
|
+ }
|
|
|
+
|
|
|
+vhost-user-input
|
|
|
+----------------
|
|
|
+
|
|
|
+Command line options:
|
|
|
+
|
|
|
+--evdev-path=PATH
|
|
|
+
|
|
|
+ Specify the linux input device.
|
|
|
+
|
|
|
+ (optional)
|
|
|
+
|
|
|
+--no-grab
|
|
|
+
|
|
|
+ Do no request exclusive access to the input device.
|
|
|
+
|
|
|
+ (optional)
|
|
|
+
|
|
|
+vhost-user-gpu
|
|
|
+--------------
|
|
|
+
|
|
|
+Command line options:
|
|
|
+
|
|
|
+--render-node=PATH
|
|
|
+
|
|
|
+ Specify the GPU DRM render node.
|
|
|
+
|
|
|
+ (optional)
|
|
|
+
|
|
|
+--virgl
|
|
|
+
|
|
|
+ Enable virgl rendering support.
|
|
|
+
|
|
|
+ (optional)
|
Marc-André Lureau