From: Pierrick Bouvier <pierrick.bouv...@linaro.org> Reviewed-by: Richard Henderson <richard.hender...@linaro.org> Signed-off-by: Pierrick Bouvier <pierrick.bouv...@linaro.org> Message-Id: <20241209183104.365796-7-pierrick.bouv...@linaro.org> [AJB: update MAINTAINERS] Signed-off-by: Alex Bennée <alex.ben...@linaro.org> Message-Id: <20250116160306.1709518-37-alex.ben...@linaro.org>
diff --git a/MAINTAINERS b/MAINTAINERS index 4c86c81f08..846b81e3ec 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -79,6 +79,7 @@ F: docs/devel/conflict-resolution.rst F: docs/devel/style.rst F: docs/devel/submitting-a-patch.rst F: docs/devel/submitting-a-pull-request.rst +F: docs/glossary.rst Responsible Disclosure, Reporting Security Issues ------------------------------------------------- diff --git a/docs/devel/control-flow-integrity.rst b/docs/devel/control-flow-integrity.rst index e6b73a4fe1..3d5702fa4c 100644 --- a/docs/devel/control-flow-integrity.rst +++ b/docs/devel/control-flow-integrity.rst @@ -1,3 +1,5 @@ +.. _cfi: + ============================ Control-Flow Integrity (CFI) ============================ diff --git a/docs/devel/multi-thread-tcg.rst b/docs/devel/multi-thread-tcg.rst index d706c27ea7..7fd0a07633 100644 --- a/docs/devel/multi-thread-tcg.rst +++ b/docs/devel/multi-thread-tcg.rst @@ -4,6 +4,8 @@ This work is licensed under the terms of the GNU GPL, version 2 or later. See the COPYING file in the top-level directory. +.. _mttcg: + ================== Multi-threaded TCG ================== diff --git a/docs/glossary.rst b/docs/glossary.rst new file mode 100644 index 0000000000..693d9855dd --- /dev/null +++ b/docs/glossary.rst @@ -0,0 +1,280 @@ +.. _Glossary: + +-------- +Glossary +-------- + +This section of the manual presents brief definitions of acronyms and terms used +by QEMU developers. + +Accelerator +----------- + +A specific API used to accelerate execution of guest instructions. It can be +hardware-based, through a virtualization API provided by the host OS (kvm, hvf, +whpx, ...), or software-based (tcg). See this description of `supported +accelerators<Accelerators>`. + +Board +----- + +Another name for :ref:`machine`. + +Block +----- + +Block drivers are the available `disk formats and front-ends +<block-drivers>` available, and block devices `(see Block device section on +options page)<sec_005finvocation>` are using them to implement disks for a +virtual machine. + +CFI +--- + +Control Flow Integrity is a hardening technique used to prevent exploits +targeting QEMU by detecting unexpected branches during execution. QEMU `actively +supports<cfi>` being compiled with CFI enabled. + +Device +------ + +In QEMU, a device is a piece of hardware visible to the guest. Examples include +UARTs, PCI controllers, PCI cards, VGA controllers, and many more. + +QEMU is able to emulate a CPU, and all the hardware interacting with it, +including `many devices<device-emulation>`. When QEMU runs a virtual machine +using a hardware-based accelerator, it is responsible for emulating, using +software, all devices. + +EDK2 +---- + +EDK2, as known as `TianoCore <https://www.tianocore.org/>`_, is an open source +implementation of UEFI standard. QEMU virtual machines that boot a UEFI firmware +usually use EDK2. + +gdbstub +------- + +QEMU implements a `gdb server <GDB usage>`, allowing gdb to attach to it and +debug a running virtual machine, or a program in user-mode. This allows +debugging the guest code that is running inside QEMU. + +glib2 +----- + +`GLib2 <https://docs.gtk.org/glib/>`_ is one of the most important libraries we +are using through the codebase. It provides many data structures, macros, string +and thread utilities and portable functions across different OS. It's required +to build QEMU. + +Guest agent +----------- + +The `QEMU Guest Agent <qemu-ga>` is a daemon intended to be run within virtual +machines. It provides various services to help QEMU to interact with it. + +.. _guest: + +Guest +----- + +Guest is the architecture of the virtual machine, which is emulated. +See also :ref:`host`. + +Sometimes this is called the :ref:`target` architecture, but that term +can be ambiguous. + +.. _host: + +Host +---- + +Host is the architecture on which QEMU is running on, which is native. +See also :ref:`guest`. + +Hypervisor +---------- + +The formal definition of an hypervisor is a program or API than can be used to +manage a virtual machine. QEMU is a virtualizer, that interacts with various +hypervisors. + +In the context of QEMU, an hypervisor is an API, provided by the Host OS, +allowing to execute virtual machines. Linux implementation is KVM (and supports +Xen as well). For MacOS, it's HVF. Windows defines WHPX. And NetBSD provides +NVMM. + +.. _machine: + +Machine +------- + +QEMU's system emulation models many different types of hardware. A machine model +(sometimes called a board model) is the model of a complete virtual system with +RAM, one or more CPUs, and various devices. It can be selected with the option +``-machine`` of qemu-system. Our machine models can be found on this `page +<system-targets-ref>`. + +Migration +--------- + +QEMU can save and restore the execution of a virtual machine between different +host systems. This is provided by the `Migration framework<migration>`. + +NBD +--- + +The `QEMU Network Block Device server <qemu-nbd>` is a tool that can be used to +mount and access QEMU images, providing functionality similar to a loop device. + +Mailing List +------------ + +This is `where <https://wiki.qemu.org/Contribute/MailingLists>`_ all the +development happens! Changes are posted as series, that all developers can +review and share feedback for. + +For reporting issues, our `GitLab +<https://gitlab.com/qemu-project/qemu/-/issues>`_ tracker is the best place. + +.. _softmmu: + +MMU / softmmu +------------- + +The Memory Management Unit is responsible for translating virtual addresses to +physical addresses and managing memory protection. QEMU system mode is named +"softmmu" precisely because it implements this in software, including a TLB +(Translation lookaside buffer), for the guest virtual machine. + +QEMU user-mode does not implement a full software MMU, but "simply" translates +virtual addresses by adding a specific offset, and relying on host MMU/OS +instead. + +Monitor / QMP / HMP +------------------- + +The `QEMU Monitor <QEMU monitor>` is a text interface which can be used to interact +with a running virtual machine. + +QMP stands for QEMU Monitor Protocol and is a json based interface. +HMP stands for Human Monitor Protocol and is a set of text commands available +for users who prefer natural language to json. + +MTTCG +----- + +Multiple CPU support was first implemented using a round-robin algorithm +running on a single thread. Later on, `Multi-threaded TCG <mttcg>` was developed +to benefit from multiple cores to speed up execution. + +Plugins +------- + +`TCG Plugins <TCG Plugins>` is an API used to instrument guest code, in system +and user mode. The end goal is to have a similar set of functionality compared +to `DynamoRIO <https://dynamorio.org/>`_ or `valgrind <https://valgrind.org/>`_. + +One key advantage of QEMU plugins is that they can be used to perform +architecture agnostic instrumentation. + +Patchew +------- + +`Patchew <https://patchew.org/QEMU/>`_ is a website that tracks patches on the +Mailing List. + +PR +-- + +Once a series is reviewed and accepted by a subsystem maintainer, it will be +included in a PR (Pull Request) that the project maintainer will merge into QEMU +main branch, after running tests. + +The QEMU project doesn't currently expect most developers to directly submit +pull requests. + +QCOW2 +----- + +QEMU Copy On Write is a disk format developed by QEMU. It provides transparent +compression, automatic extension, and many other advantages over a raw image. + +qcow2 is the recommended format to use. + +QEMU +---- + +`QEMU (Quick Emulator) <https://www.qemu.org/>`_ is a generic and open source +machine emulator and virtualizer. + +QOM +--- + +`QEMU Object Model <qom>` is an object oriented API used to define various +devices and hardware in the QEMU codebase. + +Record/replay +------------- + +`Record/replay <replay>` is a feature of QEMU allowing to have a deterministic +and reproducible execution of a virtual machine. + +Rust +---- + +`A new programming language <https://www.rust-lang.org/>`_, memory safe by +default. There is a work in progress to integrate it in QEMU codebase for +various subsystems. + +System mode +----------- + +QEMU System mode provides a virtual model of an entire machine (CPU, memory and +emulated devices) to run a guest OS. In this mode the CPU may be fully emulated, +or it may work with a hypervisor such as KVM, Xen or Hypervisor.Framework to +allow the guest to run directly on the host CPU. + +QEMU System mode is called :ref:`softmmu <softmmu>` as well. + +.. _target: + +Target +------ + +The term "target" can be ambiguous. In most places in QEMU it is used as a +synonym for :ref:`guest`. For example the code for emulating Arm CPUs is in +``target/arm/``. However in the :ref:`TCG subsystem <tcg>` "target" refers to the +architecture which QEMU is running on, i.e. the :ref:`host`. + +TCG +--- + +TCG is the QEMU `Tiny Code Generator <tcg>`. It is the JIT (just-in-time) +compiler we use to emulate a guest CPU in software. + +It is one of the accelerators supported by QEMU, and supports a lot of +guest/host architectures. + +User mode +--------- + +QEMU User mode can launch processes compiled for one CPU on another CPU. In this +mode the CPU is always emulated. In this mode, QEMU translate system calls from +guest to host kernel. It is available for Linux and BSD. + +VirtIO +------ + +VirtIO is an open standard used to define and implement virtual devices with a +minimal overhead, defining a set of data structures and hypercalls (similar to +system calls, but targeting an hypervisor, which happens to be QEMU in our +case). It's designed to be more efficient than emulating a real device, by +minimizing the amount of interactions between a guest VM and its hypervisor. + +vhost-user +---------- + +`Vhost-user <vhost_user>` is an interface used to implement VirtIO devices +outside of QEMU itself. diff --git a/docs/index.rst b/docs/index.rst index 78285ebd6a..5665de85ca 100644 --- a/docs/index.rst +++ b/docs/index.rst @@ -20,3 +20,4 @@ Welcome to QEMU's documentation! interop/index specs/index devel/index + glossary diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst index 766a7455f0..0c9c2ce035 100644 --- a/docs/system/arm/virt.rst +++ b/docs/system/arm/virt.rst @@ -1,3 +1,5 @@ +.. _arm-virt: + 'virt' generic virtual platform (``virt``) ========================================== diff --git a/docs/system/images.rst b/docs/system/images.rst index d000bd6b6f..a5551173c9 100644 --- a/docs/system/images.rst +++ b/docs/system/images.rst @@ -82,4 +82,6 @@ VM snapshots currently have the following known limitations: - A few device drivers still have incomplete snapshot support so their state is not saved or restored properly (in particular USB). +.. _block-drivers: + .. include:: qemu-block-drivers.rst.inc diff --git a/docs/tools/qemu-nbd.rst b/docs/tools/qemu-nbd.rst index 329f44d989..4f21b7904a 100644 --- a/docs/tools/qemu-nbd.rst +++ b/docs/tools/qemu-nbd.rst @@ -1,3 +1,5 @@ +.. _qemu-nbd: + ===================================== QEMU Disk Network Block Device Server ===================================== -- 2.39.5
