qemu/docs/glossary.rst

3 --------
5 --------
8 by QEMU developers.
11 -----------
14 hardware-based, through a virtualization API provided by the host OS (kvm, hvf,
15 whpx, ...), or software-based (tcg). See this description of `supported
19 -----
24 -----
26 Block drivers are the available `disk formats and front-ends
27 <block-drivers>` available, and block devices `(see Block device section on
32 ---
35 targeting QEMU by detecting unexpected branches during execution. QEMU `actively
39 ------
41 In QEMU, a device is a piece of hardware visible to the guest. Examples include
44 QEMU is able to emulate a CPU, and all the hardware interacting with it,
45 including `many devices<device-emulation>`. When QEMU runs a virtual machine
46 using a hardware-based accelerator, it is responsible for emulating, using
50 ----
53 implementation of UEFI standard. QEMU virtual machines that boot a UEFI firmware
57 -------
59 QEMU implements a `gdb server <GDB usage>`, allowing gdb to attach to it and
60 debug a running virtual machine, or a program in user-mode. This allows
61 debugging the guest code that is running inside QEMU.
64 -----
69 to build QEMU.
72 -----------
74 The `QEMU Guest Agent <qemu-ga>` is a daemon intended to be run within virtual
75 machines. It provides various services to help QEMU to interact with it.
80 -----
91 ----
93 Host is the architecture on which QEMU is running on, which is native.
97 ----------
100 manage a virtual machine. QEMU is a virtualizer, that interacts with various
103 In the context of QEMU, an hypervisor is an API, provided by the Host OS,
111 -------
113 QEMU's system emulation models many different types of hardware. A machine model
114 (sometimes called a board model) is the model of a complete virtual system with
116 ``-machine`` of qemu-system. Our machine models can be found on this `page
117 <system-targets-ref>`.
120 ---------
122 QEMU can save and restore the execution of a virtual machine between different
126 ---
128 The `QEMU Network Block Device server <qemu-nbd>` is a tool that can be used to
129 mount and access QEMU images, providing functionality similar to a loop device.
132 ------------
134 This is `where <https://wiki.qemu.org/Contribute/MailingLists>`_ all the
139 <https://gitlab.com/qemu-project/qemu/-/issues>`_ tracker is the best place.
144 -------------
147 physical addresses and managing memory protection. QEMU system mode is named
151 QEMU user-mode does not implement a full software MMU, but "simply" translates
156 -------------------
158 The `QEMU Monitor <QEMU monitor>` is a text interface which can be used to interact
161 QMP stands for QEMU Monitor Protocol and is a json based interface.
166 -----
168 Multiple CPU support was first implemented using a round-robin algorithm
169 running on a single thread. Later on, `Multi-threaded TCG <mttcg>` was developed
173 -------
175 `TCG Plugins <TCG Plugins>` is an API used to instrument guest code, in system
179 One key advantage of QEMU plugins is that they can be used to perform
183 -------
185 `Patchew <https://patchew.org/QEMU/>`_ is a website that tracks patches on the
189 --
192 included in a PR (Pull Request) that the project maintainer will merge into QEMU
195 The QEMU project doesn't currently expect most developers to directly submit
199 -----
201 QEMU Copy On Write is a disk format developed by QEMU. It provides transparent
206 QEMU  chapter
207 ----
209 `QEMU (Quick Emulator) <https://www.qemu.org/>`_ is a generic and open source
213 ---
215 :ref:`QEMU Object Model <qom>` is an object oriented API used to define
216 various devices and hardware in the QEMU codebase.
219 -------------
221 :ref:`Record/replay <replay>` is a feature of QEMU allowing to have a
225 ----
227 `A new programming language <https://www.rust-lang.org/>`_, memory safe by
228 default. There is a work in progress to integrate it in QEMU codebase for
231 System mode
232 -----------
234 QEMU System mode provides a virtual model of an entire machine (CPU, memory and
239 QEMU System mode is called :ref:`softmmu <softmmu>` as well.
244 ------
246 The term "target" can be ambiguous. In most places in QEMU it is used as a
249 architecture which QEMU is running on, i.e. the :ref:`host`.
252 ---
254 TCG is the QEMU `Tiny Code Generator <tcg>`. It is the JIT (just-in-time)
257 It is one of the accelerators supported by QEMU, and supports a lot of
261 ---------
263 QEMU User mode can launch processes compiled for one CPU on another CPU. In this
264 mode the CPU is always emulated. In this mode, QEMU translate system calls from
268 ------
272 system calls, but targeting an hypervisor, which happens to be QEMU in our
276 vhost-user
277 ----------
279 `Vhost-user <vhost_user>` is an interface used to implement VirtIO devices
280 outside of QEMU itself.