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docs/system: convert Texinfo documentation to rST 

Apart from targets.rst, which was written by hand, this is an automated
conversion obtained with the following command:

  makeinfo --force -o - --docbook \
    -D 'qemu_system_x86 QEMU_SYSTEM_X86_MACRO' \
    -D 'qemu_system     QEMU_SYSTEM_MACRO' \
    $texi | pandoc -f docbook -t rst+smart | perl -e '
      $/=undef;
      $_ = <>;
      s/^-  − /-  /gm;
      s/QEMU_SYSTEM_MACRO/|qemu_system|/g;
      s/QEMU_SYSTEM_X86_MACRO/|qemu_system_x86|/g;
      s/(?=::\n\n +\|qemu)/.. parsed-literal/g;
      s/:\n\n::$/::/gm;
      print' > $rst

In addition, the following changes were made manually:

- target-i386.rst and target-mips.rst: replace CPU model documentation with
  an include directive

- monitor.rst: replace the command section with a comment

- images.rst: add toctree

- target-arm.rst: Replace use of :math: (which Sphinx complains
  about) with :sup:, and hide it behind |I2C| and |I2C| substitutions.

Content that is not @included remains exclusive to qemu-doc.texi.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20200228153619.9906-20-peter.maydell@linaro.org
Message-id: 20200226113034.6741-19-pbonzini@redhat.com
[PMM: Fixed target-arm.rst use of :math:; remove out of date
 note about images.rst from commit message; fixed expansion
 of |qemu_system_x86|; use parsed-literal in invocation.rst
 when we want to use |qemu_system_x86|; fix incorrect subsection
 level for "OS requirements" in target-i386.rst; fix incorrect
 syntax for making links to other sections of the manual]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Paolo Bonzini 2020-02-28 15:36:05 +00:00 committed by Peter Maydell
parent 41fba1618b
commit 324b2298fe
26 changed files with 2207 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
docs/defs.rst.inc
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all rST files as part of the epilogue by docs/conf.py. conf.py
also defines some dynamically generated substitutions like CONFDIR.
Note that |qemu_system| is intended to be used inside a parsed-literal
block: the definition must not include extra literal formatting with
``..``: this works in the HTML output but the manpages will end up
misrendered with following normal text incorrectly in boldface.
Note that |qemu_system| and |qemu_system_x86| are intended to be
used inside a parsed-literal block: the definition must not include
extra literal formatting with ``..``: this works in the HTML output
but the manpages will end up misrendered with following normal text
incorrectly in boldface.
.. |qemu_system| replace:: qemu-system-x86_64
.. |qemu_system_x86| replace:: qemu_system-x86_64
.. |I2C| replace:: I\ :sup:`2`\ C
.. |I2S| replace:: I\ :sup:`2`\ S

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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 https://repology.org is a useful resource to identify
currently shipped versions of software in various operating systems,
though it does not cover all distros listed below.
Linux OS
--------
For distributions with frequent, short-lifetime releases, the project
will aim to support all versions that are not end of life by their
respective vendors. For the purposes of identifying supported software
versions, the project will look at Fedora, Ubuntu, and openSUSE distros.
Other short- lifetime distros will be assumed to ship similar software
versions.
For distributions with long-lifetime releases, the project will aim 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 it reaches "end of life". For the purposes
of identifying supported software versions, the project will look at
RHEL, Debian, Ubuntu LTS, and SLES distros. Other long-lifetime distros
will be assumed to ship similar software versions.
Windows
-------
The project supports building with current versions of the MinGW
toolchain, hosted on Linux.
macOS
-----
The project supports building with the two most recent versions of
macOS, with the current homebrew package set available.
FreeBSD
-------
The project aims to support the all the versions which are not end of
life.
NetBSD
------
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.
OpenBSD
-------
The project aims to support the all the versions which are not end of
life.

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.. _gdb_005fusage:
GDB usage
---------
QEMU has a primitive support to work with gdb, so that you can do
'Ctrl-C' while the virtual machine is running and inspect its state.
In order to use gdb, launch QEMU with the '-s' option. It will wait for
a gdb connection:
.. parsed-literal::
|qemu_system| -s -kernel bzImage -hda rootdisk.img -append "root=/dev/hda"
Connected to host network interface: tun0
Waiting gdb connection on port 1234
Then launch gdb on the 'vmlinux' executable::
> gdb vmlinux
In gdb, connect to QEMU::
(gdb) target remote localhost:1234
Then you can use gdb normally. For example, type 'c' to launch the
kernel::
(gdb) c
Here are some useful tips in order to use gdb on system code:
1. Use ``info reg`` to display all the CPU registers.
2. Use ``x/10i $eip`` to display the code at the PC position.
3. Use ``set architecture i8086`` to dump 16 bit code. Then use
``x/10i $cs*16+$eip`` to dump the code at the PC position.
Advanced debugging options:
The default single stepping behavior is step with the IRQs and timer
service routines off. It is set this way because when gdb executes a
single step it expects to advance beyond the current instruction. With
the IRQs and timer service routines on, a single step might jump into
the one of the interrupt or exception vectors instead of executing the
current instruction. This means you may hit the same breakpoint a number
of times before executing the instruction gdb wants to have executed.
Because there are rare circumstances where you want to single step into
an interrupt vector the behavior can be controlled from GDB. There are
three commands you can query and set the single step behavior:
``maintenance packet qqemu.sstepbits``
This will display the MASK bits used to control the single stepping
IE:
::
(gdb) maintenance packet qqemu.sstepbits
sending: "qqemu.sstepbits"
received: "ENABLE=1,NOIRQ=2,NOTIMER=4"
``maintenance packet qqemu.sstep``
This will display the current value of the mask used when single
stepping IE:
::
(gdb) maintenance packet qqemu.sstep
sending: "qqemu.sstep"
received: "0x7"
``maintenance packet Qqemu.sstep=HEX_VALUE``
This will change the single step mask, so if wanted to enable IRQs on
the single step, but not timers, you would use:
::
(gdb) maintenance packet Qqemu.sstep=0x5
sending: "qemu.sstep=0x5"
received: "OK"

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.. _disk_005fimages:
Disk Images
-----------
QEMU supports many disk image formats, including growable disk images
(their size increase as non empty sectors are written), compressed and
encrypted disk images.
.. _disk_005fimages_005fquickstart:
Quick start for disk image creation
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
You can create a disk image with the command::
qemu-img create myimage.img mysize
where myimage.img is the disk image filename and mysize is its size in
kilobytes. You can add an ``M`` suffix to give the size in megabytes and
a ``G`` suffix for gigabytes.
See the qemu-img invocation documentation for more information.
.. _disk_005fimages_005fsnapshot_005fmode:
Snapshot mode
~~~~~~~~~~~~~
If you use the option ``-snapshot``, all disk images are considered as
read only. When sectors in written, they are written in a temporary file
created in ``/tmp``. You can however force the write back to the raw
disk images by using the ``commit`` monitor command (or C-a s in the
serial console).
.. _vm_005fsnapshots:
VM snapshots
~~~~~~~~~~~~
VM snapshots are snapshots of the complete virtual machine including CPU
state, RAM, device state and the content of all the writable disks. In
order to use VM snapshots, you must have at least one non removable and
writable block device using the ``qcow2`` disk image format. Normally
this device is the first virtual hard drive.
Use the monitor command ``savevm`` to create a new VM snapshot or
replace an existing one. A human readable name can be assigned to each
snapshot in addition to its numerical ID.
Use ``loadvm`` to restore a VM snapshot and ``delvm`` to remove a VM
snapshot. ``info snapshots`` lists the available snapshots with their
associated information::
(qemu) info snapshots
Snapshot devices: hda
Snapshot list (from hda):
ID TAG VM SIZE DATE VM CLOCK
1 start 41M 2006-08-06 12:38:02 00:00:14.954
2 40M 2006-08-06 12:43:29 00:00:18.633
3 msys 40M 2006-08-06 12:44:04 00:00:23.514
A VM snapshot is made of a VM state info (its size is shown in
``info snapshots``) and a snapshot of every writable disk image. The VM
state info is stored in the first ``qcow2`` non removable and writable
block device. The disk image snapshots are stored in every disk image.
The size of a snapshot in a disk image is difficult to evaluate and is
not shown by ``info snapshots`` because the associated disk sectors are
shared among all the snapshots to save disk space (otherwise each
snapshot would need a full copy of all the disk images).
When using the (unrelated) ``-snapshot`` option
(:ref:`disk_005fimages_005fsnapshot_005fmode`),
you can always make VM snapshots, but they are deleted as soon as you
exit QEMU.
VM snapshots currently have the following known limitations:
- They cannot cope with removable devices if they are removed or
inserted after a snapshot is done.
- A few device drivers still have incomplete snapshot support so their
state is not saved or restored properly (in particular USB).
.. include:: qemu-block-drivers.rst.inc

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@ -12,8 +12,25 @@ or Hypervisor.Framework.
Contents:
.. toctree::
:maxdepth: 2
:maxdepth: 3
quickstart
invocation
keys
mux-chardev
monitor
images
net
usb
ivshmem
linuxboot
vnc-security
tls
gdb
managed-startup
targets
security
vfio-ap
deprecated
build-platforms
license

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.. _sec_005finvocation:
Invocation
----------
.. parsed-literal::
|qemu_system| [options] [disk_image]
disk_image is a raw hard disk image for IDE hard disk 0. Some targets do
not need a disk image.
Device URL Syntax
~~~~~~~~~~~~~~~~~
In addition to using normal file images for the emulated storage
devices, QEMU can also use networked resources such as iSCSI devices.
These are specified using a special URL syntax.
``iSCSI``
iSCSI support allows QEMU to access iSCSI resources directly and use
as images for the guest storage. Both disk and cdrom images are
supported.
Syntax for specifying iSCSI LUNs is
"iscsi://<target-ip>[:<port>]/<target-iqn>/<lun>"
By default qemu will use the iSCSI initiator-name
'iqn.2008-11.org.linux-kvm[:<name>]' but this can also be set from
the command line or a configuration file.
Since version Qemu 2.4 it is possible to specify a iSCSI request
timeout to detect stalled requests and force a reestablishment of the
session. The timeout is specified in seconds. The default is 0 which
means no timeout. Libiscsi 1.15.0 or greater is required for this
feature.
Example (without authentication):
.. parsed-literal::
|qemu_system| -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \
-cdrom iscsi://192.0.2.1/iqn.2001-04.com.example/2 \
-drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
Example (CHAP username/password via URL):
.. parsed-literal::
|qemu_system| -drive file=iscsi://user%password@192.0.2.1/iqn.2001-04.com.example/1
Example (CHAP username/password via environment variables):
.. parsed-literal::
LIBISCSI_CHAP_USERNAME="user" \
LIBISCSI_CHAP_PASSWORD="password" \
|qemu_system| -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
``NBD``
QEMU supports NBD (Network Block Devices) both using TCP protocol as
well as Unix Domain Sockets. With TCP, the default port is 10809.
Syntax for specifying a NBD device using TCP, in preferred URI form:
"nbd://<server-ip>[:<port>]/[<export>]"
Syntax for specifying a NBD device using Unix Domain Sockets;
remember that '?' is a shell glob character and may need quoting:
"nbd+unix:///[<export>]?socket=<domain-socket>"
Older syntax that is also recognized:
"nbd:<server-ip>:<port>[:exportname=<export>]"
Syntax for specifying a NBD device using Unix Domain Sockets
"nbd:unix:<domain-socket>[:exportname=<export>]"
Example for TCP
.. parsed-literal::
|qemu_system| --drive file=nbd:192.0.2.1:30000
Example for Unix Domain Sockets
.. parsed-literal::
|qemu_system| --drive file=nbd:unix:/tmp/nbd-socket
``SSH``
QEMU supports SSH (Secure Shell) access to remote disks.
Examples:
.. parsed-literal::
|qemu_system| -drive file=ssh://user@host/path/to/disk.img
|qemu_system| -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img
Currently authentication must be done using ssh-agent. Other
authentication methods may be supported in future.
``Sheepdog``
Sheepdog is a distributed storage system for QEMU. QEMU supports
using either local sheepdog devices or remote networked devices.
Syntax for specifying a sheepdog device
::
sheepdog[+tcp|+unix]://[host:port]/vdiname[?socket=path][#snapid|#tag]
Example
.. parsed-literal::
|qemu_system| --drive file=sheepdog://192.0.2.1:30000/MyVirtualMachine
See also https://sheepdog.github.io/sheepdog/.
``GlusterFS``
GlusterFS is a user space distributed file system. QEMU supports the
use of GlusterFS volumes for hosting VM disk images using TCP, Unix
Domain Sockets and RDMA transport protocols.
Syntax for specifying a VM disk image on GlusterFS volume is
.. parsed-literal::
URI:
gluster[+type]://[host[:port]]/volume/path[?socket=...][,debug=N][,logfile=...]
JSON:
'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol","path":"a.img","debug":N,"logfile":"...",
  "server":[{"type":"tcp","host":"...","port":"..."},
  {"type":"unix","socket":"..."}]}}'
Example
.. parsed-literal::
URI:
|qemu_system| --drive file=gluster://192.0.2.1/testvol/a.img,
  file.debug=9,file.logfile=/var/log/qemu-gluster.log
JSON:
|qemu_system| 'json:{"driver":"qcow2",
  "file":{"driver":"gluster",
  "volume":"testvol","path":"a.img",
  "debug":9,"logfile":"/var/log/qemu-gluster.log",
  "server":[{"type":"tcp","host":"1.2.3.4","port":24007},
  {"type":"unix","socket":"/var/run/glusterd.socket"}]}}'
|qemu_system| -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img,
  file.debug=9,file.logfile=/var/log/qemu-gluster.log,
  file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007,
  file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket
See also http://www.gluster.org.
``HTTP/HTTPS/FTP/FTPS``
QEMU supports read-only access to files accessed over http(s) and
ftp(s).
Syntax using a single filename:
::
<protocol>://[<username>[:<password>]@]<host>/<path>
where:
``protocol``
'http', 'https', 'ftp', or 'ftps'.
``username``
Optional username for authentication to the remote server.
``password``
Optional password for authentication to the remote server.
``host``
Address of the remote server.
``path``
Path on the remote server, including any query string.
The following options are also supported:
``url``
The full URL when passing options to the driver explicitly.
``readahead``
The amount of data to read ahead with each range request to the
remote server. This value may optionally have the suffix 'T', 'G',
'M', 'K', 'k' or 'b'. If it does not have a suffix, it will be
assumed to be in bytes. The value must be a multiple of 512 bytes.
It defaults to 256k.
``sslverify``
Whether to verify the remote server's certificate when connecting
over SSL. It can have the value 'on' or 'off'. It defaults to
'on'.
``cookie``
Send this cookie (it can also be a list of cookies separated by
';') with each outgoing request. Only supported when using
protocols such as HTTP which support cookies, otherwise ignored.
``timeout``
Set the timeout in seconds of the CURL connection. This timeout is
the time that CURL waits for a response from the remote server to
get the size of the image to be downloaded. If not set, the
default timeout of 5 seconds is used.
Note that when passing options to qemu explicitly, ``driver`` is the
value of <protocol>.
Example: boot from a remote Fedora 20 live ISO image
.. parsed-literal::
|qemu_system_x86| --drive media=cdrom,file=https://archives.fedoraproject.org/pub/archive/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
|qemu_system_x86| --drive media=cdrom,file.driver=http,file.url=http://archives.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
Example: boot from a remote Fedora 20 cloud image using a local
overlay for writes, copy-on-read, and a readahead of 64k
.. parsed-literal::
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"http",, "file.url":"http://archives.fedoraproject.org/pub/archive/fedora/linux/releases/20/Images/x86_64/Fedora-x86_64-20-20131211.1-sda.qcow2",, "file.readahead":"64k"}' /tmp/Fedora-x86_64-20-20131211.1-sda.qcow2
|qemu_system_x86| -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on
Example: boot from an image stored on a VMware vSphere server with a
self-signed certificate using a local overlay for writes, a readahead
of 64k and a timeout of 10 seconds.
.. parsed-literal::
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"https",, "file.url":"https://user:password@vsphere.example.com/folder/test/test-flat.vmdk?dcPath=Datacenter&dsName=datastore1",, "file.sslverify":"off",, "file.readahead":"64k",, "file.timeout":10}' /tmp/test.qcow2
|qemu_system_x86| -drive file=/tmp/test.qcow2

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.. _pcsys_005fivshmem:
Inter-VM Shared Memory device
-----------------------------
On Linux hosts, a shared memory device is available. The basic syntax
is:
.. parsed-literal::
|qemu_system_x86| -device ivshmem-plain,memdev=hostmem
where hostmem names a host memory backend. For a POSIX shared memory
backend, use something like
::
-object memory-backend-file,size=1M,share,mem-path=/dev/shm/ivshmem,id=hostmem
If desired, interrupts can be sent between guest VMs accessing the same
shared memory region. Interrupt support requires using a shared memory
server and using a chardev socket to connect to it. The code for the
shared memory server is qemu.git/contrib/ivshmem-server. An example
syntax when using the shared memory server is:
.. parsed-literal::
# First start the ivshmem server once and for all
ivshmem-server -p pidfile -S path -m shm-name -l shm-size -n vectors
# Then start your qemu instances with matching arguments
|qemu_system_x86| -device ivshmem-doorbell,vectors=vectors,chardev=id
-chardev socket,path=path,id=id
When using the server, the guest will be assigned a VM ID (>=0) that
allows guests using the same server to communicate via interrupts.
Guests can read their VM ID from a device register (see
ivshmem-spec.txt).
Migration with ivshmem
~~~~~~~~~~~~~~~~~~~~~~
With device property ``master=on``, the guest will copy the shared
memory on migration to the destination host. With ``master=off``, the
guest will not be able to migrate with the device attached. In the
latter case, the device should be detached and then reattached after
migration using the PCI hotplug support.
At most one of the devices sharing the same memory can be master. The
master must complete migration before you plug back the other devices.
ivshmem and hugepages
~~~~~~~~~~~~~~~~~~~~~
Instead of specifying the <shm size> using POSIX shm, you may specify a
memory backend that has hugepage support:
.. parsed-literal::
|qemu_system_x86| -object memory-backend-file,size=1G,mem-path=/dev/hugepages/my-shmem-file,share,id=mb1
-device ivshmem-plain,memdev=mb1
ivshmem-server also supports hugepages mount points with the ``-m``
memory path argument.

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.. _pcsys_005fkeys:
Keys in the graphical frontends
-------------------------------
During the graphical emulation, you can use special key combinations to
change modes. The default key mappings are shown below, but if you use
``-alt-grab`` then the modifier is Ctrl-Alt-Shift (instead of Ctrl-Alt)
and if you use ``-ctrl-grab`` then the modifier is the right Ctrl key
(instead of Ctrl-Alt):
Ctrl-Alt-f
Toggle full screen
Ctrl-Alt-+
Enlarge the screen
Ctrl-Alt\--
Shrink the screen
Ctrl-Alt-u
Restore the screen's un-scaled dimensions
Ctrl-Alt-n
Switch to virtual console 'n'. Standard console mappings are:
*1*
Target system display
*2*
Monitor
*3*
Serial port
Ctrl-Alt
Toggle mouse and keyboard grab.
In the virtual consoles, you can use Ctrl-Up, Ctrl-Down, Ctrl-PageUp and
Ctrl-PageDown to move in the back log.

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.. _License:
License
=======
QEMU is a trademark of Fabrice Bellard.
QEMU is released under the `GNU General Public
License <https://www.gnu.org/licenses/gpl-2.0.txt>`__, version 2. Parts
of QEMU have specific licenses, see file
`LICENSE <https://git.qemu.org/?p=qemu.git;a=blob_plain;f=LICENSE>`__.

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.. _direct_005flinux_005fboot:
Direct Linux Boot
-----------------
This section explains how to launch a Linux kernel inside QEMU without
having to make a full bootable image. It is very useful for fast Linux
kernel testing.
The syntax is:
.. parsed-literal::
|qemu_system| -kernel bzImage -hda rootdisk.img -append "root=/dev/hda"
Use ``-kernel`` to provide the Linux kernel image and ``-append`` to
give the kernel command line arguments. The ``-initrd`` option can be
used to provide an INITRD image.
If you do not need graphical output, you can disable it and redirect the
virtual serial port and the QEMU monitor to the console with the
``-nographic`` option. The typical command line is:
.. parsed-literal::
|qemu_system| -kernel bzImage -hda rootdisk.img \
-append "root=/dev/hda console=ttyS0" -nographic
Use Ctrl-a c to switch between the serial console and the monitor (see
:ref:`pcsys_005fkeys`).

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.. _pcsys_005fmonitor:
QEMU Monitor
------------
The QEMU monitor is used to give complex commands to the QEMU emulator.
You can use it to:
- Remove or insert removable media images (such as CD-ROM or
floppies).
- Freeze/unfreeze the Virtual Machine (VM) and save or restore its
state from a disk file.
- Inspect the VM state without an external debugger.
..
The commands section goes here once it's converted from Texinfo to RST.
Integer expressions
~~~~~~~~~~~~~~~~~~~
The monitor understands integers expressions for every integer argument.
You can use register names to get the value of specifics CPU registers
by prefixing them with *$*.

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.. _mux_005fkeys:
Keys in the character backend multiplexer
-----------------------------------------
During emulation, if you are using a character backend multiplexer
(which is the default if you are using ``-nographic``) then several
commands are available via an escape sequence. These key sequences all
start with an escape character, which is Ctrl-a by default, but can be
changed with ``-echr``. The list below assumes you're using the default.
Ctrl-a h
Print this help
Ctrl-a x
Exit emulator
Ctrl-a s
Save disk data back to file (if -snapshot)
Ctrl-a t
Toggle console timestamps
Ctrl-a b
Send break (magic sysrq in Linux)
Ctrl-a c
Rotate between the frontends connected to the multiplexer (usually
this switches between the monitor and the console)
Ctrl-a Ctrl-a
Send the escape character to the frontend

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.. _pcsys_005fnetwork:
Network emulation
-----------------
QEMU can simulate several network cards (e.g. PCI or ISA cards on the PC
target) and can connect them to a network backend on the host or an
emulated hub. The various host network backends can either be used to
connect the NIC of the guest to a real network (e.g. by using a TAP
devices or the non-privileged user mode network stack), or to other
guest instances running in another QEMU process (e.g. by using the
socket host network backend).
Using TAP network interfaces
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This is the standard way to connect QEMU to a real network. QEMU adds a
virtual network device on your host (called ``tapN``), and you can then
configure it as if it was a real ethernet card.
Linux host
^^^^^^^^^^
As an example, you can download the ``linux-test-xxx.tar.gz`` archive
and copy the script ``qemu-ifup`` in ``/etc`` and configure properly
``sudo`` so that the command ``ifconfig`` contained in ``qemu-ifup`` can
be executed as root. You must verify that your host kernel supports the
TAP network interfaces: the device ``/dev/net/tun`` must be present.
See :ref:`sec_005finvocation` to have examples of command
lines using the TAP network interfaces.
Windows host
^^^^^^^^^^^^
There is a virtual ethernet driver for Windows 2000/XP systems, called
TAP-Win32. But it is not included in standard QEMU for Windows, so you
will need to get it separately. It is part of OpenVPN package, so
download OpenVPN from : https://openvpn.net/.
Using the user mode network stack
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
By using the option ``-net user`` (default configuration if no ``-net``
option is specified), QEMU uses a completely user mode network stack
(you don't need root privilege to use the virtual network). The virtual
network configuration is the following::
guest (10.0.2.15) <------> Firewall/DHCP server <-----> Internet
| (10.0.2.2)
|
----> DNS server (10.0.2.3)
|
----> SMB server (10.0.2.4)
The QEMU VM behaves as if it was behind a firewall which blocks all
incoming connections. You can use a DHCP client to automatically
configure the network in the QEMU VM. The DHCP server assign addresses
to the hosts starting from 10.0.2.15.
In order to check that the user mode network is working, you can ping
the address 10.0.2.2 and verify that you got an address in the range
10.0.2.x from the QEMU virtual DHCP server.
Note that ICMP traffic in general does not work with user mode
networking. ``ping``, aka. ICMP echo, to the local router (10.0.2.2)
shall work, however. If you're using QEMU on Linux >= 3.0, it can use
unprivileged ICMP ping sockets to allow ``ping`` to the Internet. The
host admin has to set the ping_group_range in order to grant access to
those sockets. To allow ping for GID 100 (usually users group)::
echo 100 100 > /proc/sys/net/ipv4/ping_group_range
When using the built-in TFTP server, the router is also the TFTP server.
When using the ``'-netdev user,hostfwd=...'`` option, TCP or UDP
connections can be redirected from the host to the guest. It allows for
example to redirect X11, telnet or SSH connections.
Hubs
~~~~
QEMU can simulate several hubs. A hub can be thought of as a virtual
connection between several network devices. These devices can be for
example QEMU virtual ethernet cards or virtual Host ethernet devices
(TAP devices). You can connect guest NICs or host network backends to
such a hub using the ``-netdev
hubport`` or ``-nic hubport`` options. The legacy ``-net`` option also
connects the given device to the emulated hub with ID 0 (i.e. the
default hub) unless you specify a netdev with ``-net nic,netdev=xxx``
here.
Connecting emulated networks between QEMU instances
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Using the ``-netdev socket`` (or ``-nic socket`` or ``-net socket``)
option, it is possible to create emulated networks that span several
QEMU instances. See the description of the ``-netdev socket`` option in
:ref:`sec_005finvocation` to have a basic
example.

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.. _pcsys_005fquickstart:
Quick Start
-----------
Download and uncompress a PC hard disk image with Linux installed (e.g.
``linux.img``) and type:
.. parsed-literal::
|qemu_system| linux.img
Linux should boot and give you a prompt.

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.. _ARM-System-emulator:
ARM System emulator
-------------------
Use the executable ``qemu-system-arm`` to simulate a ARM machine. The
ARM Integrator/CP board is emulated with the following devices:
- ARM926E, ARM1026E, ARM946E, ARM1136 or Cortex-A8 CPU
- Two PL011 UARTs
- SMC 91c111 Ethernet adapter
- PL110 LCD controller
- PL050 KMI with PS/2 keyboard and mouse.
- PL181 MultiMedia Card Interface with SD card.
The ARM Versatile baseboard is emulated with the following devices:
- ARM926E, ARM1136 or Cortex-A8 CPU
- PL190 Vectored Interrupt Controller
- Four PL011 UARTs
- SMC 91c111 Ethernet adapter
- PL110 LCD controller
- PL050 KMI with PS/2 keyboard and mouse.
- PCI host bridge. Note the emulated PCI bridge only provides access
to PCI memory space. It does not provide access to PCI IO space. This
means some devices (eg. ne2k_pci NIC) are not usable, and others (eg.
rtl8139 NIC) are only usable when the guest drivers use the memory
mapped control registers.
- PCI OHCI USB controller.
- LSI53C895A PCI SCSI Host Bus Adapter with hard disk and CD-ROM
devices.
- PL181 MultiMedia Card Interface with SD card.
Several variants of the ARM RealView baseboard are emulated, including
the EB, PB-A8 and PBX-A9. Due to interactions with the bootloader, only
certain Linux kernel configurations work out of the box on these boards.
Kernels for the PB-A8 board should have CONFIG_REALVIEW_HIGH_PHYS_OFFSET
enabled in the kernel, and expect 512M RAM. Kernels for The PBX-A9 board
should have CONFIG_SPARSEMEM enabled, CONFIG_REALVIEW_HIGH_PHYS_OFFSET
disabled and expect 1024M RAM.
The following devices are emulated:
- ARM926E, ARM1136, ARM11MPCore, Cortex-A8 or Cortex-A9 MPCore CPU
- ARM AMBA Generic/Distributed Interrupt Controller
- Four PL011 UARTs
- SMC 91c111 or SMSC LAN9118 Ethernet adapter
- PL110 LCD controller
- PL050 KMI with PS/2 keyboard and mouse
- PCI host bridge
- PCI OHCI USB controller
- LSI53C895A PCI SCSI Host Bus Adapter with hard disk and CD-ROM
devices
- PL181 MultiMedia Card Interface with SD card.
The XScale-based clamshell PDA models (\"Spitz\", \"Akita\", \"Borzoi\"
and \"Terrier\") emulation includes the following peripherals:
- Intel PXA270 System-on-chip (ARM V5TE core)
- NAND Flash memory
- IBM/Hitachi DSCM microdrive in a PXA PCMCIA slot - not in \"Akita\"
- On-chip OHCI USB controller
- On-chip LCD controller
- On-chip Real Time Clock
- TI ADS7846 touchscreen controller on SSP bus
- Maxim MAX1111 analog-digital converter on |I2C| bus
- GPIO-connected keyboard controller and LEDs
- Secure Digital card connected to PXA MMC/SD host
- Three on-chip UARTs
- WM8750 audio CODEC on |I2C| and |I2S| busses
The Palm Tungsten|E PDA (codename \"Cheetah\") emulation includes the
following elements:
- Texas Instruments OMAP310 System-on-chip (ARM 925T core)
- ROM and RAM memories (ROM firmware image can be loaded with
-option-rom)
- On-chip LCD controller
- On-chip Real Time Clock
- TI TSC2102i touchscreen controller / analog-digital converter /
Audio CODEC, connected through MicroWire and |I2S| busses
- GPIO-connected matrix keypad
- Secure Digital card connected to OMAP MMC/SD host
- Three on-chip UARTs
Nokia N800 and N810 internet tablets (known also as RX-34 and RX-44 /
48) emulation supports the following elements:
- Texas Instruments OMAP2420 System-on-chip (ARM 1136 core)
- RAM and non-volatile OneNAND Flash memories
- Display connected to EPSON remote framebuffer chip and OMAP on-chip
display controller and a LS041y3 MIPI DBI-C controller
- TI TSC2301 (in N800) and TI TSC2005 (in N810) touchscreen
controllers driven through SPI bus
- National Semiconductor LM8323-controlled qwerty keyboard driven
through |I2C| bus
- Secure Digital card connected to OMAP MMC/SD host
- Three OMAP on-chip UARTs and on-chip STI debugging console
- Mentor Graphics \"Inventra\" dual-role USB controller embedded in a
TI TUSB6010 chip - only USB host mode is supported
- TI TMP105 temperature sensor driven through |I2C| bus
- TI TWL92230C power management companion with an RTC on
|I2C| bus
- Nokia RETU and TAHVO multi-purpose chips with an RTC, connected
through CBUS
The Luminary Micro Stellaris LM3S811EVB emulation includes the following
devices:
- Cortex-M3 CPU core.
- 64k Flash and 8k SRAM.
- Timers, UARTs, ADC and |I2C| interface.
- OSRAM Pictiva 96x16 OLED with SSD0303 controller on
|I2C| bus.
The Luminary Micro Stellaris LM3S6965EVB emulation includes the
following devices:
- Cortex-M3 CPU core.
- 256k Flash and 64k SRAM.
- Timers, UARTs, ADC, |I2C| and SSI interfaces.
- OSRAM Pictiva 128x64 OLED with SSD0323 controller connected via
SSI.
The Freecom MusicPal internet radio emulation includes the following
elements:
- Marvell MV88W8618 ARM core.
- 32 MB RAM, 256 KB SRAM, 8 MB flash.
- Up to 2 16550 UARTs
- MV88W8xx8 Ethernet controller
- MV88W8618 audio controller, WM8750 CODEC and mixer
- 128x64 display with brightness control
- 2 buttons, 2 navigation wheels with button function
The Siemens SX1 models v1 and v2 (default) basic emulation. The
emulation includes the following elements:
- Texas Instruments OMAP310 System-on-chip (ARM 925T core)
- ROM and RAM memories (ROM firmware image can be loaded with
-pflash) V1 1 Flash of 16MB and 1 Flash of 8MB V2 1 Flash of 32MB
- On-chip LCD controller
- On-chip Real Time Clock
- Secure Digital card connected to OMAP MMC/SD host
- Three on-chip UARTs
A Linux 2.6 test image is available on the QEMU web site. More
information is available in the QEMU mailing-list archive.
The following options are specific to the ARM emulation:
``-semihosting``
Enable semihosting syscall emulation.
On ARM this implements the \"Angel\" interface.
Note that this allows guest direct access to the host filesystem, so
should only be used with trusted guest OS.

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.. _QEMU-PC-System-emulator:
x86 (PC) System emulator
------------------------
.. _pcsys_005fdevices:
Peripherals
~~~~~~~~~~~
The QEMU PC System emulator simulates the following peripherals:
- i440FX host PCI bridge and PIIX3 PCI to ISA bridge
- Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs VESA
extensions (hardware level, including all non standard modes).
- PS/2 mouse and keyboard
- 2 PCI IDE interfaces with hard disk and CD-ROM support
- Floppy disk
- PCI and ISA network adapters
- Serial ports
- IPMI BMC, either and internal or external one
- Creative SoundBlaster 16 sound card
- ENSONIQ AudioPCI ES1370 sound card
- Intel 82801AA AC97 Audio compatible sound card
- Intel HD Audio Controller and HDA codec
- Adlib (OPL2) - Yamaha YM3812 compatible chip
- Gravis Ultrasound GF1 sound card
- CS4231A compatible sound card
- PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual USB-1.1
hub.
SMP is supported with up to 255 CPUs.
QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL
VGA BIOS.
QEMU uses YM3812 emulation by Tatsuyuki Satoh.
QEMU uses GUS emulation (GUSEMU32 http://www.deinmeister.de/gusemu/) by
Tibor \"TS\" Schütz.
Note that, by default, GUS shares IRQ(7) with parallel ports and so QEMU
must be told to not have parallel ports to have working GUS.
.. parsed-literal::
|qemu_system_x86| dos.img -soundhw gus -parallel none
Alternatively:
.. parsed-literal::
|qemu_system_x86| dos.img -device gus,irq=5
Or some other unclaimed IRQ.
CS4231A is the chip used in Windows Sound System and GUSMAX products
.. include:: cpu-models-x86.rst.inc
.. _pcsys_005freq:
OS requirements
~~~~~~~~~~~~~~~
On x86_64 hosts, the default set of CPU features enabled by the KVM
accelerator require the host to be running Linux v4.5 or newer. Red Hat
Enterprise Linux 7 is also supported, since the required
functionality was backported.

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.. _ColdFire-System-emulator:
ColdFire System emulator
------------------------
Use the executable ``qemu-system-m68k`` to simulate a ColdFire machine.
The emulator is able to boot a uClinux kernel.
The M5208EVB emulation includes the following devices:
- MCF5208 ColdFire V2 Microprocessor (ISA A+ with EMAC).
- Three Two on-chip UARTs.
- Fast Ethernet Controller (FEC)
The AN5206 emulation includes the following devices:
- MCF5206 ColdFire V2 Microprocessor.
- Two on-chip UARTs.
The following options are specific to the ColdFire emulation:
``-semihosting``
Enable semihosting syscall emulation.
On M68K this implements the \"ColdFire GDB\" interface used by
libgloss.
Note that this allows guest direct access to the host filesystem, so
should only be used with trusted guest OS.

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.. _MIPS-System-emulator:
MIPS System emulator
--------------------
Four executables cover simulation of 32 and 64-bit MIPS systems in both
endian options, ``qemu-system-mips``, ``qemu-system-mipsel``
``qemu-system-mips64`` and ``qemu-system-mips64el``. Five different
machine types are emulated:
- A generic ISA PC-like machine \"mips\"
- The MIPS Malta prototype board \"malta\"
- An ACER Pica \"pica61\". This machine needs the 64-bit emulator.
- MIPS emulator pseudo board \"mipssim\"
- A MIPS Magnum R4000 machine \"magnum\". This machine needs the
64-bit emulator.
The generic emulation is supported by Debian 'Etch' and is able to
install Debian into a virtual disk image. The following devices are
emulated:
- A range of MIPS CPUs, default is the 24Kf
- PC style serial port
- PC style IDE disk
- NE2000 network card
The Malta emulation supports the following devices:
- Core board with MIPS 24Kf CPU and Galileo system controller
- PIIX4 PCI/USB/SMbus controller
- The Multi-I/O chip's serial device
- PCI network cards (PCnet32 and others)
- Malta FPGA serial device
- Cirrus (default) or any other PCI VGA graphics card
The Boston board emulation supports the following devices:
- Xilinx FPGA, which includes a PCIe root port and an UART
- Intel EG20T PCH connects the I/O peripherals, but only the SATA bus
is emulated
The ACER Pica emulation supports:
- MIPS R4000 CPU
- PC-style IRQ and DMA controllers
- PC Keyboard
- IDE controller
The MIPS Magnum R4000 emulation supports:
- MIPS R4000 CPU
- PC-style IRQ controller
- PC Keyboard
- SCSI controller
- G364 framebuffer
The Fulong 2E emulation supports:
- Loongson 2E CPU
- Bonito64 system controller as North Bridge
- VT82C686 chipset as South Bridge
- RTL8139D as a network card chipset
The mipssim pseudo board emulation provides an environment similar to
what the proprietary MIPS emulator uses for running Linux. It supports:
- A range of MIPS CPUs, default is the 24Kf
- PC style serial port
- MIPSnet network emulation
.. include:: cpu-models-mips.rst.inc
.. _nanoMIPS-System-emulator:
nanoMIPS System emulator
~~~~~~~~~~~~~~~~~~~~~~~~
Executable ``qemu-system-mipsel`` also covers simulation of 32-bit
nanoMIPS system in little endian mode:
- nanoMIPS I7200 CPU
Example of ``qemu-system-mipsel`` usage for nanoMIPS is shown below:
Download ``<disk_image_file>`` from
https://mipsdistros.mips.com/LinuxDistro/nanomips/buildroot/index.html.
Download ``<kernel_image_file>`` from
https://mipsdistros.mips.com/LinuxDistro/nanomips/kernels/v4.15.18-432-gb2eb9a8b07a1-20180627102142/index.html.
Start system emulation of Malta board with nanoMIPS I7200 CPU::
qemu-system-mipsel -cpu I7200 -kernel <kernel_image_file> \
-M malta -serial stdio -m <memory_size> -hda <disk_image_file> \
-append "mem=256m@0x0 rw console=ttyS0 vga=cirrus vesa=0x111 root=/dev/sda"

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.. _PowerPC-System-emulator:
PowerPC System emulator
-----------------------
Use the executable ``qemu-system-ppc`` to simulate a complete 40P (PREP)
or PowerMac PowerPC system.
QEMU emulates the following PowerMac peripherals:
- UniNorth or Grackle PCI Bridge
- PCI VGA compatible card with VESA Bochs Extensions
- 2 PMAC IDE interfaces with hard disk and CD-ROM support
- NE2000 PCI adapters
- Non Volatile RAM
- VIA-CUDA with ADB keyboard and mouse.
QEMU emulates the following 40P (PREP) peripherals:
- PCI Bridge
- PCI VGA compatible card with VESA Bochs Extensions
- 2 IDE interfaces with hard disk and CD-ROM support
- Floppy disk
- PCnet network adapters
- Serial port
- PREP Non Volatile RAM
- PC compatible keyboard and mouse.
Since version 0.9.1, QEMU uses OpenBIOS https://www.openbios.org/ for
the g3beige and mac99 PowerMac and the 40p machines. OpenBIOS is a free
(GPL v2) portable firmware implementation. The goal is to implement a
100% IEEE 1275-1994 (referred to as Open Firmware) compliant firmware.
The following options are specific to the PowerPC emulation:
``-g WxH[xDEPTH]``
Set the initial VGA graphic mode. The default is 800x600x32.
``-prom-env string``
Set OpenBIOS variables in NVRAM, for example:
::
qemu-system-ppc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=hd:2,\yaboot' \
-prom-env 'boot-args=conf=hd:2,\yaboot.conf'
More information is available at
http://perso.magic.fr/l_indien/qemu-ppc/.

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.. _Sparc32-System-emulator:
Sparc32 System emulator
-----------------------
Use the executable ``qemu-system-sparc`` to simulate the following Sun4m
architecture machines:
- SPARCstation 4
- SPARCstation 5
- SPARCstation 10
- SPARCstation 20
- SPARCserver 600MP
- SPARCstation LX
- SPARCstation Voyager
- SPARCclassic
- SPARCbook
The emulation is somewhat complete. SMP up to 16 CPUs is supported, but
Linux limits the number of usable CPUs to 4.
QEMU emulates the following sun4m peripherals:
- IOMMU
- TCX or cgthree Frame buffer
- Lance (Am7990) Ethernet
- Non Volatile RAM M48T02/M48T08
- Slave I/O: timers, interrupt controllers, Zilog serial ports,
keyboard and power/reset logic
- ESP SCSI controller with hard disk and CD-ROM support
- Floppy drive (not on SS-600MP)
- CS4231 sound device (only on SS-5, not working yet)
The number of peripherals is fixed in the architecture. Maximum memory
size depends on the machine type, for SS-5 it is 256MB and for others
2047MB.
Since version 0.8.2, QEMU uses OpenBIOS https://www.openbios.org/.
OpenBIOS is a free (GPL v2) portable firmware implementation. The goal
is to implement a 100% IEEE 1275-1994 (referred to as Open Firmware)
compliant firmware.
A sample Linux 2.6 series kernel and ram disk image are available on the
QEMU web site. There are still issues with NetBSD and OpenBSD, but most
kernel versions work. Please note that currently older Solaris kernels
don't work probably due to interface issues between OpenBIOS and
Solaris.
The following options are specific to the Sparc32 emulation:
``-g WxHx[xDEPTH]``
Set the initial graphics mode. For TCX, the default is 1024x768x8
with the option of 1024x768x24. For cgthree, the default is
1024x768x8 with the option of 1152x900x8 for people who wish to use
OBP.
``-prom-env string``
Set OpenBIOS variables in NVRAM, for example:
::
qemu-system-sparc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'
``-M [SS-4|SS-5|SS-10|SS-20|SS-600MP|LX|Voyager|SPARCClassic] [|SPARCbook]``
Set the emulated machine type. Default is SS-5.

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.. _Sparc64-System-emulator:
Sparc64 System emulator
-----------------------
Use the executable ``qemu-system-sparc64`` to simulate a Sun4u
(UltraSPARC PC-like machine), Sun4v (T1 PC-like machine), or generic
Niagara (T1) machine. The Sun4u emulator is mostly complete, being able
to run Linux, NetBSD and OpenBSD in headless (-nographic) mode. The
Sun4v emulator is still a work in progress.
The Niagara T1 emulator makes use of firmware and OS binaries supplied
in the S10image/ directory of the OpenSPARC T1 project
http://download.oracle.com/technetwork/systems/opensparc/OpenSPARCT1_Arch.1.5.tar.bz2
and is able to boot the disk.s10hw2 Solaris image.
::
qemu-system-sparc64 -M niagara -L /path-to/S10image/ \
-nographic -m 256 \
-drive if=pflash,readonly=on,file=/S10image/disk.s10hw2
QEMU emulates the following peripherals:
- UltraSparc IIi APB PCI Bridge
- PCI VGA compatible card with VESA Bochs Extensions
- PS/2 mouse and keyboard
- Non Volatile RAM M48T59
- PC-compatible serial ports
- 2 PCI IDE interfaces with hard disk and CD-ROM support
- Floppy disk
The following options are specific to the Sparc64 emulation:
``-prom-env string``
Set OpenBIOS variables in NVRAM, for example:
::
qemu-system-sparc64 -prom-env 'auto-boot?=false'
``-M [sun4u|sun4v|niagara]``
Set the emulated machine type. The default is sun4u.

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.. _Xtensa-System-emulator:
Xtensa System emulator
----------------------
Two executables cover simulation of both Xtensa endian options,
``qemu-system-xtensa`` and ``qemu-system-xtensaeb``. Two different
machine types are emulated:
- Xtensa emulator pseudo board \"sim\"
- Avnet LX60/LX110/LX200 board
The sim pseudo board emulation provides an environment similar to one
provided by the proprietary Tensilica ISS. It supports:
- A range of Xtensa CPUs, default is the DC232B
- Console and filesystem access via semihosting calls
The Avnet LX60/LX110/LX200 emulation supports:
- A range of Xtensa CPUs, default is the DC232B
- 16550 UART
- OpenCores 10/100 Mbps Ethernet MAC
The following options are specific to the Xtensa emulation:
``-semihosting``
Enable semihosting syscall emulation.
Xtensa semihosting provides basic file IO calls, such as
open/read/write/seek/select. Tensilica baremetal libc for ISS and
linux platform \"sim\" use this interface.
Note that this allows guest direct access to the host filesystem, so
should only be used with trusted guest OS.

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QEMU System Emulator Targets
============================
QEMU is a generic emulator and it emulates many machines. Most of the
options are similar for all machines. Specific information about the
various targets are mentioned in the following sections.
Contents:
.. toctree::
target-i386
target-ppc
target-sparc
target-sparc64
target-mips
target-arm
target-m68k
target-xtensa

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.. _network_005ftls:
TLS setup for network services
------------------------------
Almost all network services in QEMU have the ability to use TLS for
session data encryption, along with x509 certificates for simple client
authentication. What follows is a description of how to generate
certificates suitable for usage with QEMU, and applies to the VNC
server, character devices with the TCP backend, NBD server and client,
and migration server and client.
At a high level, QEMU requires certificates and private keys to be
provided in PEM format. Aside from the core fields, the certificates
should include various extension data sets, including v3 basic
constraints data, key purpose, key usage and subject alt name.
The GnuTLS package includes a command called ``certtool`` which can be
used to easily generate certificates and keys in the required format
with expected data present. Alternatively a certificate management
service may be used.
At a minimum it is necessary to setup a certificate authority, and issue
certificates to each server. If using x509 certificates for
authentication, then each client will also need to be issued a
certificate.
Assuming that the QEMU network services will only ever be exposed to
clients on a private intranet, there is no need to use a commercial
certificate authority to create certificates. A self-signed CA is
sufficient, and in fact likely to be more secure since it removes the
ability of malicious 3rd parties to trick the CA into mis-issuing certs
for impersonating your services. The only likely exception where a
commercial CA might be desirable is if enabling the VNC websockets
server and exposing it directly to remote browser clients. In such a
case it might be useful to use a commercial CA to avoid needing to
install custom CA certs in the web browsers.
The recommendation is for the server to keep its certificates in either
``/etc/pki/qemu`` or for unprivileged users in ``$HOME/.pki/qemu``.
.. _tls_005fgenerate_005fca:
Setup the Certificate Authority
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This step only needs to be performed once per organization /
organizational unit. First the CA needs a private key. This key must be
kept VERY secret and secure. If this key is compromised the entire trust
chain of the certificates issued with it is lost.
::
# certtool --generate-privkey > ca-key.pem
To generate a self-signed certificate requires one core piece of
information, the name of the organization. A template file ``ca.info``
should be populated with the desired data to avoid having to deal with
interactive prompts from certtool::
# cat > ca.info <<EOF
cn = Name of your organization
ca
cert_signing_key
EOF
# certtool --generate-self-signed \
--load-privkey ca-key.pem
--template ca.info \
--outfile ca-cert.pem
The ``ca`` keyword in the template sets the v3 basic constraints
extension to indicate this certificate is for a CA, while
``cert_signing_key`` sets the key usage extension to indicate this will
be used for signing other keys. The generated ``ca-cert.pem`` file
should be copied to all servers and clients wishing to utilize TLS
support in the VNC server. The ``ca-key.pem`` must not be
disclosed/copied anywhere except the host responsible for issuing
certificates.
.. _tls_005fgenerate_005fserver:
Issuing server certificates
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Each server (or host) needs to be issued with a key and certificate.
When connecting the certificate is sent to the client which validates it
against the CA certificate. The core pieces of information for a server
certificate are the hostnames and/or IP addresses that will be used by
clients when connecting. The hostname / IP address that the client
specifies when connecting will be validated against the hostname(s) and
IP address(es) recorded in the server certificate, and if no match is
found the client will close the connection.
Thus it is recommended that the server certificate include both the
fully qualified and unqualified hostnames. If the server will have
permanently assigned IP address(es), and clients are likely to use them
when connecting, they may also be included in the certificate. Both IPv4
and IPv6 addresses are supported. Historically certificates only
included 1 hostname in the ``CN`` field, however, usage of this field
for validation is now deprecated. Instead modern TLS clients will
validate against the Subject Alt Name extension data, which allows for
multiple entries. In the future usage of the ``CN`` field may be
discontinued entirely, so providing SAN extension data is strongly
recommended.
On the host holding the CA, create template files containing the
information for each server, and use it to issue server certificates.
::
# cat > server-hostNNN.info <<EOF
organization = Name of your organization
cn = hostNNN.foo.example.com
dns_name = hostNNN
dns_name = hostNNN.foo.example.com
ip_address = 10.0.1.87
ip_address = 192.8.0.92
ip_address = 2620:0:cafe::87
ip_address = 2001:24::92
tls_www_server
encryption_key
signing_key
EOF
# certtool --generate-privkey > server-hostNNN-key.pem
# certtool --generate-certificate \
--load-ca-certificate ca-cert.pem \
--load-ca-privkey ca-key.pem \
--load-privkey server-hostNNN-key.pem \
--template server-hostNNN.info \
--outfile server-hostNNN-cert.pem
The ``dns_name`` and ``ip_address`` fields in the template are setting
the subject alt name extension data. The ``tls_www_server`` keyword is
the key purpose extension to indicate this certificate is intended for
usage in a web server. Although QEMU network services are not in fact
HTTP servers (except for VNC websockets), setting this key purpose is
still recommended. The ``encryption_key`` and ``signing_key`` keyword is
the key usage extension to indicate this certificate is intended for
usage in the data session.
The ``server-hostNNN-key.pem`` and ``server-hostNNN-cert.pem`` files
should now be securely copied to the server for which they were
generated, and renamed to ``server-key.pem`` and ``server-cert.pem``
when added to the ``/etc/pki/qemu`` directory on the target host. The
``server-key.pem`` file is security sensitive and should be kept
protected with file mode 0600 to prevent disclosure.
.. _tls_005fgenerate_005fclient:
Issuing client certificates
~~~~~~~~~~~~~~~~~~~~~~~~~~~
The QEMU x509 TLS credential setup defaults to enabling client
verification using certificates, providing a simple authentication
mechanism. If this default is used, each client also needs to be issued
a certificate. The client certificate contains enough metadata to
uniquely identify the client with the scope of the certificate
authority. The client certificate would typically include fields for
organization, state, city, building, etc.
Once again on the host holding the CA, create template files containing
the information for each client, and use it to issue client
certificates.
::
# cat > client-hostNNN.info <<EOF
country = GB
state = London
locality = City Of London
organization = Name of your organization
cn = hostNNN.foo.example.com
tls_www_client
encryption_key
signing_key
EOF
# certtool --generate-privkey > client-hostNNN-key.pem
# certtool --generate-certificate \
--load-ca-certificate ca-cert.pem \
--load-ca-privkey ca-key.pem \
--load-privkey client-hostNNN-key.pem \
--template client-hostNNN.info \
--outfile client-hostNNN-cert.pem
The subject alt name extension data is not required for clients, so the
the ``dns_name`` and ``ip_address`` fields are not included. The
``tls_www_client`` keyword is the key purpose extension to indicate this
certificate is intended for usage in a web client. Although QEMU network
clients are not in fact HTTP clients, setting this key purpose is still
recommended. The ``encryption_key`` and ``signing_key`` keyword is the
key usage extension to indicate this certificate is intended for usage
in the data session.
The ``client-hostNNN-key.pem`` and ``client-hostNNN-cert.pem`` files
should now be securely copied to the client for which they were
generated, and renamed to ``client-key.pem`` and ``client-cert.pem``
when added to the ``/etc/pki/qemu`` directory on the target host. The
``client-key.pem`` file is security sensitive and should be kept
protected with file mode 0600 to prevent disclosure.
If a single host is going to be using TLS in both a client and server
role, it is possible to create a single certificate to cover both roles.
This would be quite common for the migration and NBD services, where a
QEMU process will be started by accepting a TLS protected incoming
migration, and later itself be migrated out to another host. To generate
a single certificate, simply include the template data from both the
client and server instructions in one.
::
# cat > both-hostNNN.info <<EOF
country = GB
state = London
locality = City Of London
organization = Name of your organization
cn = hostNNN.foo.example.com
dns_name = hostNNN
dns_name = hostNNN.foo.example.com
ip_address = 10.0.1.87
ip_address = 192.8.0.92
ip_address = 2620:0:cafe::87
ip_address = 2001:24::92
tls_www_server
tls_www_client
encryption_key
signing_key
EOF
# certtool --generate-privkey > both-hostNNN-key.pem
# certtool --generate-certificate \
--load-ca-certificate ca-cert.pem \
--load-ca-privkey ca-key.pem \
--load-privkey both-hostNNN-key.pem \
--template both-hostNNN.info \
--outfile both-hostNNN-cert.pem
When copying the PEM files to the target host, save them twice, once as
``server-cert.pem`` and ``server-key.pem``, and again as
``client-cert.pem`` and ``client-key.pem``.
.. _tls_005fcreds_005fsetup:
TLS x509 credential configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
QEMU has a standard mechanism for loading x509 credentials that will be
used for network services and clients. It requires specifying the
``tls-creds-x509`` class name to the ``--object`` command line argument
for the system emulators. Each set of credentials loaded should be given
a unique string identifier via the ``id`` parameter. A single set of TLS
credentials can be used for multiple network backends, so VNC,
migration, NBD, character devices can all share the same credentials.
Note, however, that credentials for use in a client endpoint must be
loaded separately from those used in a server endpoint.
When specifying the object, the ``dir`` parameters specifies which
directory contains the credential files. This directory is expected to
contain files with the names mentioned previously, ``ca-cert.pem``,
``server-key.pem``, ``server-cert.pem``, ``client-key.pem`` and
``client-cert.pem`` as appropriate. It is also possible to include a set
of pre-generated Diffie-Hellman (DH) parameters in a file
``dh-params.pem``, which can be created using the
``certtool --generate-dh-params`` command. If omitted, QEMU will
dynamically generate DH parameters when loading the credentials.
The ``endpoint`` parameter indicates whether the credentials will be
used for a network client or server, and determines which PEM files are
loaded.
The ``verify`` parameter determines whether x509 certificate validation
should be performed. This defaults to enabled, meaning clients will
always validate the server hostname against the certificate subject alt
name fields and/or CN field. It also means that servers will request
that clients provide a certificate and validate them. Verification
should never be turned off for client endpoints, however, it may be
turned off for server endpoints if an alternative mechanism is used to
authenticate clients. For example, the VNC server can use SASL to
authenticate clients instead.
To load server credentials with client certificate validation enabled
.. parsed-literal::
|qemu_system| -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server
while to load client credentials use
.. parsed-literal::
|qemu_system| -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=client
Network services which support TLS will all have a ``tls-creds``
parameter which expects the ID of the TLS credentials object. For
example with VNC:
.. parsed-literal::
|qemu_system| -vnc 0.0.0.0:0,tls-creds=tls0
.. _tls_005fpsk:
TLS Pre-Shared Keys (PSK)
~~~~~~~~~~~~~~~~~~~~~~~~~
Instead of using certificates, you may also use TLS Pre-Shared Keys
(TLS-PSK). This can be simpler to set up than certificates but is less
scalable.
Use the GnuTLS ``psktool`` program to generate a ``keys.psk`` file
containing one or more usernames and random keys::
mkdir -m 0700 /tmp/keys
psktool -u rich -p /tmp/keys/keys.psk
TLS-enabled servers such as qemu-nbd can use this directory like so::
qemu-nbd \
-t -x / \
--object tls-creds-psk,id=tls0,endpoint=server,dir=/tmp/keys \
--tls-creds tls0 \
image.qcow2
When connecting from a qemu-based client you must specify the directory
containing ``keys.psk`` and an optional username (defaults to "qemu")::
qemu-img info \
--object tls-creds-psk,id=tls0,dir=/tmp/keys,username=rich,endpoint=client \
--image-opts \
file.driver=nbd,file.host=localhost,file.port=10809,file.tls-creds=tls0,file.export=/

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.. _pcsys_005fusb:
USB emulation
-------------
QEMU can emulate a PCI UHCI, OHCI, EHCI or XHCI USB controller. You can
plug virtual USB devices or real host USB devices (only works with
certain host operating systems). QEMU will automatically create and
connect virtual USB hubs as necessary to connect multiple USB devices.
.. _usb_005fdevices:
Connecting USB devices
~~~~~~~~~~~~~~~~~~~~~~
USB devices can be connected with the ``-device usb-...`` command line
option or the ``device_add`` monitor command. Available devices are:
``usb-mouse``
Virtual Mouse. This will override the PS/2 mouse emulation when
activated.
``usb-tablet``
Pointer device that uses absolute coordinates (like a touchscreen).
This means QEMU is able to report the mouse position without having
to grab the mouse. Also overrides the PS/2 mouse emulation when
activated.
``usb-storage,drive=drive_id``
Mass storage device backed by drive_id (see
:ref:`disk_005fimages`)
``usb-uas``
USB attached SCSI device, see
`usb-storage.txt <https://git.qemu.org/?p=qemu.git;a=blob_plain;f=docs/usb-storage.txt>`__
for details
``usb-bot``
Bulk-only transport storage device, see
`usb-storage.txt <https://git.qemu.org/?p=qemu.git;a=blob_plain;f=docs/usb-storage.txt>`__
for details here, too
``usb-mtp,rootdir=dir``
Media transfer protocol device, using dir as root of the file tree
that is presented to the guest.
``usb-host,hostbus=bus,hostaddr=addr``
Pass through the host device identified by bus and addr
``usb-host,vendorid=vendor,productid=product``
Pass through the host device identified by vendor and product ID
``usb-wacom-tablet``
Virtual Wacom PenPartner tablet. This device is similar to the
``tablet`` above but it can be used with the tslib library because in
addition to touch coordinates it reports touch pressure.
``usb-kbd``
Standard USB keyboard. Will override the PS/2 keyboard (if present).
``usb-serial,chardev=id``
Serial converter. This emulates an FTDI FT232BM chip connected to
host character device id.
``usb-braille,chardev=id``
Braille device. This will use BrlAPI to display the braille output on
a real or fake device referenced by id.
``usb-net[,netdev=id]``
Network adapter that supports CDC ethernet and RNDIS protocols. id
specifies a netdev defined with ``-netdev …,id=id``. For instance,
user-mode networking can be used with
.. parsed-literal::
|qemu_system| [...] -netdev user,id=net0 -device usb-net,netdev=net0
``usb-ccid``
Smartcard reader device
``usb-audio``
USB audio device
.. _host_005fusb_005fdevices:
Using host USB devices on a Linux host
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
WARNING: this is an experimental feature. QEMU will slow down when using
it. USB devices requiring real time streaming (i.e. USB Video Cameras)
are not supported yet.
1. If you use an early Linux 2.4 kernel, verify that no Linux driver is
actually using the USB device. A simple way to do that is simply to
disable the corresponding kernel module by renaming it from
``mydriver.o`` to ``mydriver.o.disabled``.
2. Verify that ``/proc/bus/usb`` is working (most Linux distributions
should enable it by default). You should see something like that:
::
ls /proc/bus/usb
001 devices drivers
3. Since only root can access to the USB devices directly, you can
either launch QEMU as root or change the permissions of the USB
devices you want to use. For testing, the following suffices:
::
chown -R myuid /proc/bus/usb
4. Launch QEMU and do in the monitor:
::
info usbhost
Device 1.2, speed 480 Mb/s
Class 00: USB device 1234:5678, USB DISK
You should see the list of the devices you can use (Never try to use
hubs, it won't work).
5. Add the device in QEMU by using:
::
device_add usb-host,vendorid=0x1234,productid=0x5678
Normally the guest OS should report that a new USB device is plugged.
You can use the option ``-device usb-host,...`` to do the same.
6. Now you can try to use the host USB device in QEMU.
When relaunching QEMU, you may have to unplug and plug again the USB
device to make it work again (this is a bug).

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.. _vnc_005fsecurity:
VNC security
------------
The VNC server capability provides access to the graphical console of
the guest VM across the network. This has a number of security
considerations depending on the deployment scenarios.
.. _vnc_005fsec_005fnone:
Without passwords
~~~~~~~~~~~~~~~~~
The simplest VNC server setup does not include any form of
authentication. For this setup it is recommended to restrict it to
listen on a UNIX domain socket only. For example
.. parsed-literal::
|qemu_system| [...OPTIONS...] -vnc unix:/home/joebloggs/.qemu-myvm-vnc
This ensures that only users on local box with read/write access to that
path can access the VNC server. To securely access the VNC server from a
remote machine, a combination of netcat+ssh can be used to provide a
secure tunnel.
.. _vnc_005fsec_005fpassword:
With passwords
~~~~~~~~~~~~~~
The VNC protocol has limited support for password based authentication.
Since the protocol limits passwords to 8 characters it should not be
considered to provide high security. The password can be fairly easily
brute-forced by a client making repeat connections. For this reason, a
VNC server using password authentication should be restricted to only
listen on the loopback interface or UNIX domain sockets. Password
authentication is not supported when operating in FIPS 140-2 compliance
mode as it requires the use of the DES cipher. Password authentication
is requested with the ``password`` option, and then once QEMU is running
the password is set with the monitor. Until the monitor is used to set
the password all clients will be rejected.
.. parsed-literal::
|qemu_system| [...OPTIONS...] -vnc :1,password -monitor stdio
(qemu) change vnc password
Password: ********
(qemu)
.. _vnc_005fsec_005fcertificate:
With x509 certificates
~~~~~~~~~~~~~~~~~~~~~~
The QEMU VNC server also implements the VeNCrypt extension allowing use
of TLS for encryption of the session, and x509 certificates for
authentication. The use of x509 certificates is strongly recommended,
because TLS on its own is susceptible to man-in-the-middle attacks.
Basic x509 certificate support provides a secure session, but no
authentication. This allows any client to connect, and provides an
encrypted session.
.. parsed-literal::
|qemu_system| [...OPTIONS...] \
-object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=no \
-vnc :1,tls-creds=tls0 -monitor stdio
In the above example ``/etc/pki/qemu`` should contain at least three
files, ``ca-cert.pem``, ``server-cert.pem`` and ``server-key.pem``.
Unprivileged users will want to use a private directory, for example
``$HOME/.pki/qemu``. NB the ``server-key.pem`` file should be protected
with file mode 0600 to only be readable by the user owning it.
.. _vnc_005fsec_005fcertificate_005fverify:
With x509 certificates and client verification
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Certificates can also provide a means to authenticate the client
connecting. The server will request that the client provide a
certificate, which it will then validate against the CA certificate.
This is a good choice if deploying in an environment with a private
internal certificate authority. It uses the same syntax as previously,
but with ``verify-peer`` set to ``yes`` instead.
.. parsed-literal::
|qemu_system| [...OPTIONS...] \
-object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=yes \
-vnc :1,tls-creds=tls0 -monitor stdio
.. _vnc_005fsec_005fcertificate_005fpw:
With x509 certificates, client verification and passwords
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Finally, the previous method can be combined with VNC password
authentication to provide two layers of authentication for clients.
.. parsed-literal::
|qemu_system| [...OPTIONS...] \
-object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=yes \
-vnc :1,tls-creds=tls0,password -monitor stdio
(qemu) change vnc password
Password: ********
(qemu)
.. _vnc_005fsec_005fsasl:
With SASL authentication
~~~~~~~~~~~~~~~~~~~~~~~~
The SASL authentication method is a VNC extension, that provides an
easily extendable, pluggable authentication method. This allows for
integration with a wide range of authentication mechanisms, such as PAM,
GSSAPI/Kerberos, LDAP, SQL databases, one-time keys and more. The
strength of the authentication depends on the exact mechanism
configured. If the chosen mechanism also provides a SSF layer, then it
will encrypt the datastream as well.
Refer to the later docs on how to choose the exact SASL mechanism used
for authentication, but assuming use of one supporting SSF, then QEMU
can be launched with:
.. parsed-literal::
|qemu_system| [...OPTIONS...] -vnc :1,sasl -monitor stdio
.. _vnc_005fsec_005fcertificate_005fsasl:
With x509 certificates and SASL authentication
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If the desired SASL authentication mechanism does not supported SSF
layers, then it is strongly advised to run it in combination with TLS
and x509 certificates. This provides securely encrypted data stream,
avoiding risk of compromising of the security credentials. This can be
enabled, by combining the 'sasl' option with the aforementioned TLS +
x509 options:
.. parsed-literal::
|qemu_system| [...OPTIONS...] \
-object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server,verify-peer=yes \
-vnc :1,tls-creds=tls0,sasl -monitor stdio
.. _vnc_005fsetup_005fsasl:
Configuring SASL mechanisms
~~~~~~~~~~~~~~~~~~~~~~~~~~~
The following documentation assumes use of the Cyrus SASL implementation
on a Linux host, but the principles should apply to any other SASL
implementation or host. When SASL is enabled, the mechanism
configuration will be loaded from system default SASL service config
/etc/sasl2/qemu.conf. If running QEMU as an unprivileged user, an
environment variable SASL_CONF_PATH can be used to make it search
alternate locations for the service config file.
If the TLS option is enabled for VNC, then it will provide session
encryption, otherwise the SASL mechanism will have to provide
encryption. In the latter case the list of possible plugins that can be
used is drastically reduced. In fact only the GSSAPI SASL mechanism
provides an acceptable level of security by modern standards. Previous
versions of QEMU referred to the DIGEST-MD5 mechanism, however, it has
multiple serious flaws described in detail in RFC 6331 and thus should
never be used any more. The SCRAM-SHA-1 mechanism provides a simple
username/password auth facility similar to DIGEST-MD5, but does not
support session encryption, so can only be used in combination with TLS.
When not using TLS the recommended configuration is
::
mech_list: gssapi
keytab: /etc/qemu/krb5.tab
This says to use the 'GSSAPI' mechanism with the Kerberos v5 protocol,
with the server principal stored in /etc/qemu/krb5.tab. For this to work
the administrator of your KDC must generate a Kerberos principal for the
server, with a name of 'qemu/somehost.example.com@EXAMPLE.COM' replacing
'somehost.example.com' with the fully qualified host name of the machine
running QEMU, and 'EXAMPLE.COM' with the Kerberos Realm.
When using TLS, if username+password authentication is desired, then a
reasonable configuration is
::
mech_list: scram-sha-1
sasldb_path: /etc/qemu/passwd.db
The ``saslpasswd2`` program can be used to populate the ``passwd.db``
file with accounts.
Other SASL configurations will be left as an exercise for the reader.
Note that all mechanisms, except GSSAPI, should be combined with use of
TLS to ensure a secure data channel.