Merge tag 'pull-jan-omnibus-020223-1' of https://gitlab.com/stsquad/qemu into staging

Testing, docs, semihosting and plugin updates

  - update playbooks for custom runners
  - add section timing support to gitlab
  - upgrade fedora images to 37
  - purge perl from the build system and deps
  - disable unstable tests in CI
  - improve intro, emulation and semihosting docs
  - semihosting bug fix and O_BINARY default
  - add memory-sve test
  - fix some races in qht
  - improve plugin handling of memory helpers
  - optimise plugin hooks
  - fix some plugin deadlocks
  - reduce win64-cross build time by dropping some targets

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* tag 'pull-jan-omnibus-020223-1' of https://gitlab.com/stsquad/qemu: (36 commits)
  gitlab: cut even more from cross-win64-system build
  plugins: Iterate on cb_lists in qemu_plugin_user_exit
  cpu-exec: assert that plugin_mem_cbs is NULL after execution
  tcg: exclude non-memory effecting helpers from instrumentation
  translator: always pair plugin_gen_insn_{start, end} calls
  plugins: fix optimization in plugin_gen_disable_mem_helpers
  plugins: make qemu_plugin_user_exit's locking order consistent with fork_start's
  util/qht: use striped locks under TSAN
  thread: de-const qemu_spin_destroy
  util/qht: add missing atomic_set(hashes[i])
  cpu: free cpu->tb_jmp_cache with RCU
  tests/tcg: add memory-sve test for aarch64
  semihosting: add O_BINARY flag in host_open for NT compatibility
  semihosting: Write back semihosting data before completion callback
  docs: add an introduction to the system docs
  semihosting: add semihosting section to the docs
  docs: add a new section to outline emulation support
  docs: add hotlinks to about preface text
  MAINTAINERS: Fix the entry for tests/tcg/nios2
  gitlab: wrap up test results for custom runners
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 220 insertions, 0 deletions

diff --git a/docs/system/introduction.rst b/docs/system/introduction.rst
new file mode 100644
index 0000000000..c8a9fe6c1d
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+++ b/docs/system/introduction.rst
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+Introduction
+============
+
+Virtualisation Accelerators
+---------------------------
+
+QEMU's system emulation provides a virtual model of a machine (CPU,
+memory and emulated devices) to run a guest OS. It supports a number
+of hypervisors (known as accelerators) as well as a JIT known as the
+Tiny Code Generator (TCG) capable of emulating many CPUs.
+
+.. list-table:: Supported Accelerators
+  :header-rows: 1
+
+  * - Accelerator
+    - Host OS
+    - Host Architectures
+  * - KVM
+    - Linux
+    - Arm (64 bit only), MIPS, PPC, RISC-V, s390x, x86
+  * - Xen
+    - Linux (as dom0)
+    - Arm, x86
+  * - Intel HAXM (hax)
+    - Linux, Windows
+    - x86
+  * - Hypervisor Framework (hvf)
+    - MacOS
+    - x86 (64 bit only), Arm (64 bit only)
+  * - Windows Hypervisor Platform (wphx)
+    - Windows
+    - x86
+  * - NetBSD Virtual Machine Monitor (nvmm)
+    - NetBSD
+    - x86
+  * - Tiny Code Generator (tcg)
+    - Linux, other POSIX, Windows, MacOS
+    - Arm, x86, Loongarch64, MIPS, PPC, s390x, Sparc64
+
+Feature Overview
+----------------
+
+System emulation provides a wide range of device models to emulate
+various hardware components you may want to add to your machine. This
+includes a wide number of VirtIO devices which are specifically tuned
+for efficient operation under virtualisation. Some of the device
+emulation can be offloaded from the main QEMU process using either
+vhost-user (for VirtIO) or :ref:`Multi-process QEMU`. If the platform
+supports it QEMU also supports directly passing devices through to
+guest VMs to eliminate the device emulation overhead. See
+:ref:`device-emulation` for more details.
+
+There is a full :ref:`featured block layer<Live Block Operations>`
+which allows for construction of complex storage topology which can be
+stacked across multiple layers supporting redirection, networking,
+snapshots and migration support.
+
+The flexible ``chardev`` system allows for handling IO from character
+like devices using stdio, files, unix sockets and TCP networking.
+
+QEMU provides a number of management interfaces including a line based
+:ref:`Human Monitor Protocol (HMP)<QEMU monitor>` that allows you to
+dynamically add and remove devices as well as introspect the system
+state. The :ref:`QEMU Monitor Protocol<QMP Ref>` (QMP) is a well
+defined, versioned, machine usable API that presents a rich interface
+to other tools to create, control and manage Virtual Machines. This is
+the interface used by higher level tools interfaces such as `Virt
+Manager <https://virt-manager.org/>`_ using the `libvirt framework
+<https://libvirt.org>`_.
+
+For the common accelerators QEMU, supported debugging with its
+:ref:`gdbstub<GDB usage>` which allows users to connect GDB and debug
+system software images.
+
+Running
+-------
+
+QEMU provides a rich and complex API which can be overwhelming to
+understand. While some architectures can boot something with just a
+disk image, those examples elide a lot of details with defaults that
+may not be optimal for modern systems.
+
+For a non-x86 system where we emulate a broad range of machine types,
+the command lines are generally more explicit in defining the machine
+and boot behaviour. You will find often find example command lines in
+the :ref:`system-targets-ref` section of the manual.
+
+While the project doesn't want to discourage users from using the
+command line to launch VMs, we do want to highlight that there are a
+number of projects dedicated to providing a more user friendly
+experience. Those built around the ``libvirt`` framework can make use
+of feature probing to build modern VM images tailored to run on the
+hardware you have.
+
+That said, the general form of a QEMU command line can be expressed
+as:
+
+.. parsed-literal::
+
+  $ |qemu_system| [machine opts] \\
+                  [cpu opts] \\
+                  [accelerator opts] \\
+                  [device opts] \\
+                  [backend opts] \\
+                  [interface opts] \\
+                  [boot opts]
+
+Most options will generate some help information. So for example:
+
+.. parsed-literal::
+
+   $ |qemu_system| -M help
+
+will list the machine types supported by that QEMU binary. ``help``
+can also be passed as an argument to another option. For example:
+
+.. parsed-literal::
+
+  $ |qemu_system| -device scsi-hd,help
+
+will list the arguments and their default values of additional options
+that can control the behaviour of the ``scsi-hd`` device.
+
+.. list-table:: Options Overview
+  :header-rows: 1
+  :widths: 10, 90
+
+  * - Options
+    -
+  * - Machine
+    - Define the machine type, amount of memory etc
+  * - CPU
+    - Type and number/topology of vCPUs. Most accelerators offer
+      a ``host`` cpu option which simply passes through your host CPU
+      configuration without filtering out any features.
+  * - Accelerator
+    - This will depend on the hypervisor you run. Note that the
+      default is TCG, which is purely emulated, so you must specify an
+      accelerator type to take advantage of hardware virtualization.
+  * - Devices
+    - Additional devices that are not defined by default with the
+      machine type.
+  * - Backends
+    - Backends are how QEMU deals with the guest's data, for example
+      how a block device is stored, how network devices see the
+      network or how a serial device is directed to the outside world.
+  * - Interfaces
+    - How the system is displayed, how it is managed and controlled or
+      debugged.
+  * - Boot
+    - How the system boots, via firmware or direct kernel boot.
+
+In the following example we first define a ``virt`` machine which is a
+general purpose platform for running Aarch64 guests. We enable
+virtualisation so we can use KVM inside the emulated guest. As the
+``virt`` machine comes with some built in pflash devices we give them
+names so we can override the defaults later.
+
+.. code::
+
+ $ qemu-system-aarch64 \
+    -machine type=virt,virtualization=on,pflash0=rom,pflash1=efivars \
+    -m 4096 \
+
+We then define the 4 vCPUs using the ``max`` option which gives us all
+the Arm features QEMU is capable of emulating. We enable a more
+emulation friendly implementation of Arm's pointer authentication
+algorithm. We explicitly specify TCG acceleration even though QEMU
+would default to it anyway.
+
+.. code::
+
+ -cpu max,pauth-impdef=on \
+ -smp 4 \
+ -accel tcg \
+
+As the ``virt`` platform doesn't have any default network or storage
+devices we need to define them. We give them ids so we can link them
+with the backend later on.
+
+.. code::
+
+ -device virtio-net-pci,netdev=unet \
+ -device virtio-scsi-pci \
+ -device scsi-hd,drive=hd \
+
+We connect the user-mode networking to our network device. As
+user-mode networking isn't directly accessible from the outside world
+we forward localhost port 2222 to the ssh port on the guest.
+
+.. code::
+
+ -netdev user,id=unet,hostfwd=tcp::2222-:22 \
+
+We connect the guest visible block device to an LVM partition we have
+set aside for our guest.
+
+.. code::
+
+ -blockdev driver=raw,node-name=hd,file.driver=host_device,file.filename=/dev/lvm-disk/debian-bullseye-arm64 \
+
+We then tell QEMU to multiplex the :ref:`QEMU monitor` with the serial
+port output (we can switch between the two using :ref:`keys in the
+character backend multiplexer`). As there is no default graphical
+device we disable the display as we can work entirely in the terminal.
+
+.. code::
+
+ -serial mon:stdio \
+ -display none \
+
+Finally we override the default firmware to ensure we have some
+storage for EFI to persist its configuration. That firmware is
+responsible for finding the disk, booting grub and eventually running
+our system.
+
+.. code::
+
+ -blockdev node-name=rom,driver=file,filename=(pwd)/pc-bios/edk2-aarch64-code.fd,read-only=true \
+ -blockdev node-name=efivars,driver=file,filename=$HOME/images/qemu-arm64-efivars