qemu/docs/glossary.rst

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13 A specific API used to accelerate execution of guest instructions. It can be
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
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24 -----
26 Block drivers are the available `disk formats and front-ends
27 <block-drivers>` available, and block devices `(see Block device section on
28 options page)<sec_005finvocation>` are using them to implement disks for a
32 ---
34 Control Flow Integrity is a hardening technique used to prevent exploits
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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
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53 implementation of UEFI standard. QEMU virtual machines that boot a UEFI firmware
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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
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74 The `QEMU Guest Agent <qemu-ga>` is a daemon intended to be run within virtual
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91 ----
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99 The formal definition of an hypervisor is a program or API than can be used to
100 manage a virtual machine. QEMU is a virtualizer, that interacts with various
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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>`.
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122 QEMU can save and restore the execution of a virtual machine between different
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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.
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139 <https://gitlab.com/qemu-project/qemu/-/issues>`_ tracker is the best place.
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148 "softmmu" precisely because it implements this in software, including a TLB
151 QEMU user-mode does not implement a full software MMU, but "simply" translates
152 virtual addresses by adding a specific offset, and relying on host MMU/OS
156 -------------------
158 The `QEMU Monitor <QEMU monitor>` is a text interface which can be used to interact
159 with a running virtual machine.
161 QMP stands for QEMU Monitor Protocol and is a json based interface.
162 HMP stands for Human Monitor Protocol and is a set of text commands available
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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
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176 and user mode. The end goal is to have a similar set of functionality compared
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185 `Patchew <https://patchew.org/QEMU/>`_ is a website that tracks patches on the
189 --
191 Once a series is reviewed and accepted by a subsystem maintainer, it will be
192 included in a PR (Pull Request) that the project maintainer will merge into QEMU
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201 QEMU Copy On Write is a disk format developed by QEMU. It provides transparent
202 compression, automatic extension, and many other advantages over a raw image.
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209 `QEMU (Quick Emulator) <https://www.qemu.org/>`_ is a generic and open source
213 ---
219 -------------
221 :ref:`Record/replay <replay>` is a feature of QEMU allowing to have a
222 deterministic and reproducible execution of a virtual machine.
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
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234 QEMU System mode provides a virtual model of an entire machine (CPU, memory and
235 emulated devices) to run a guest OS. In this mode the CPU may be fully emulated,
236 or it may work with a hypervisor such as KVM, Xen or Hypervisor.Framework to
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246 The term "target" can be ambiguous. In most places in QEMU it is used as a
252 ---
254 TCG is the QEMU `Tiny Code Generator <tcg>`. It is the JIT (just-in-time)
255 compiler we use to emulate a guest CPU in software.
257 It is one of the accelerators supported by QEMU, and supports a lot of
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268 ------
270 VirtIO is an open standard used to define and implement virtual devices with a
271 minimal overhead, defining a set of data structures and hypercalls (similar to
273 case). It's designed to be more efficient than emulating a real device, by
274 minimizing the amount of interactions between a guest VM and its hypervisor.
276 vhost-user
277 ----------
279 `Vhost-user <vhost_user>` is an interface used to implement VirtIO devices