Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 97 insertions, 0 deletions

diff --git a/docs/about/build-platforms.rst b/docs/about/build-platforms.rst
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+.. _Supported-build-platforms:
+
+Supported build platforms
+=========================
+
+QEMU aims to support building and executing on multiple host OS
+platforms. This appendix outlines which platforms are the major build
+targets. These platforms are used as the basis for deciding upon the
+minimum required versions of 3rd party software QEMU depends on. The
+supported platforms are the targets for automated testing performed by
+the project when patches are submitted for review, and tested before and
+after merge.
+
+If a platform is not listed here, it does not imply that QEMU won't
+work. If an unlisted platform has comparable software versions to a
+listed platform, there is every expectation that it will work. Bug
+reports are welcome for problems encountered on unlisted platforms
+unless they are clearly older vintage than what is described here.
+
+Note that when considering software versions shipped in distros as
+support targets, QEMU considers only the version number, and assumes the
+features in that distro match the upstream release with the same
+version. In other words, if a distro backports extra features to the
+software in their distro, QEMU upstream code will not add explicit
+support for those backports, unless the feature is auto-detectable in a
+manner that works for the upstream releases too.
+
+The `Repology`_ site is a useful resource to identify
+currently shipped versions of software in various operating systems,
+though it does not cover all distros listed below.
+
+Supported host architectures
+----------------------------
+
+Those hosts are officially supported, with various accelerators:
+
+  .. list-table::
+   :header-rows: 1
+
+   * - CPU Architecture
+     - Accelerators
+   * - Arm
+     - kvm (64 bit only), tcg, xen
+   * - MIPS
+     - kvm, tcg
+   * - PPC
+     - kvm, tcg
+   * - RISC-V
+     - tcg
+   * - s390x
+     - kvm, tcg
+   * - SPARC
+     - tcg
+   * - x86
+     - hax, hvf (64 bit only), kvm, nvmm, tcg, whpx (64 bit only), xen
+
+Other host architectures are not supported. It is possible to build QEMU system
+emulation on an unsupported host architecture using the configure
+``--enable-tcg-interpreter`` option to enable the TCI support, but note that
+this is very slow and is not recommended for normal use. QEMU user emulation
+requires host-specific support for signal handling, therefore TCI won't help
+on unsupported host architectures.
+
+Non-supported architectures may be removed in the future following the
+:ref:`deprecation process<Deprecated features>`.
+
+Linux OS, macOS, FreeBSD, NetBSD, OpenBSD
+-----------------------------------------
+
+The project aims to support the most recent major version at all times. Support
+for the previous major version will be dropped 2 years after the new major
+version is released or when the vendor itself drops support, whichever comes
+first. In this context, third-party efforts to extend the lifetime of a distro
+are not considered, even when they are endorsed by the vendor (eg. Debian LTS).
+
+For the purposes of identifying supported software versions available on Linux,
+the project will look at CentOS, Debian, Fedora, openSUSE, RHEL, SLES and
+Ubuntu LTS. Other distros will be assumed to ship similar software versions.
+
+For FreeBSD and OpenBSD, decisions will be made based on the contents of the
+respective ports repository, while NetBSD will use the pkgsrc repository.
+
+For macOS, `HomeBrew`_ will be used, although `MacPorts`_ is expected to carry
+similar versions.
+
+Windows
+-------
+
+The project supports building with current versions of the MinGW toolchain,
+hosted on Linux (Debian/Fedora).
+
+The version of the Windows API that's currently targeted is Vista / Server
+2008.
+
+.. _HomeBrew: https://brew.sh/
+.. _MacPorts: https://www.macports.org/
+.. _Repology: https://repology.org/