* QEMU User space emulator::
* Implementation notes::
* Deprecated features::
+* Supported build platforms::
* License::
* Index::
@end menu
* direct_linux_boot:: Direct Linux Boot
* pcsys_usb:: USB emulation
* vnc_security:: VNC security
+* network_tls:: TLS setup for network services
* gdb_usage:: GDB usage
* pcsys_os_specific:: Target OS specific information
@end menu
@node pcsys_network
@section Network emulation
-QEMU can simulate several network cards (PCI or ISA cards on the PC
-target) and can connect them to an arbitrary number of Virtual Local
-Area Networks (VLANs). Host TAP devices can be connected to any QEMU
-VLAN. VLAN can be connected between separate instances of QEMU to
-simulate large networks. For simpler usage, a non privileged user mode
-network stack can replace the TAP device to have a basic network
-connection.
-
-@subsection VLANs
-
-QEMU simulates several VLANs. A VLAN can be symbolised 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).
+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).
@subsection Using TAP network interfaces
@example
- QEMU VLAN <------> Firewall/DHCP server <-----> Internet
+ guest (10.0.2.15) <------> Firewall/DHCP server <-----> Internet
| (10.0.2.2)
|
----> DNS server (10.0.2.3)
connections can be redirected from the host to the guest. It allows for
example to redirect X11, telnet or SSH connections.
-@subsection Connecting VLANs between QEMU instances
+@subsection 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 @option{-netdev
+hubport} or @option{-nic hubport} options. The legacy @option{-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 @option{-net nic,netdev=xxx} here.
-Using the @option{-net socket} option, it is possible to make VLANs
-that span several QEMU instances. See @ref{sec_invocation} to have a
-basic example.
+@subsection Connecting emulated networks between QEMU instances
+
+Using the @option{-netdev socket} (or @option{-nic socket} or
+@option{-net socket}) option, it is possible to create emulated
+networks that span several QEMU instances.
+See the description of the @option{-netdev socket} option in the
+@ref{sec_invocation,,Invocation chapter} to have a basic example.
@node pcsys_other_devs
@section Other Devices
* vnc_sec_certificate_pw::
* vnc_sec_sasl::
* vnc_sec_certificate_sasl::
-* vnc_generate_cert::
* vnc_setup_sasl::
@end menu
@node vnc_sec_none
qemu-system-i386 [...OPTIONS...] -vnc :1,tls,x509,sasl -monitor stdio
@end example
+@node vnc_setup_sasl
+
+@subsection 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
+
+@example
+mech_list: gssapi
+keytab: /etc/qemu/krb5.tab
+@end example
-@node vnc_generate_cert
-@subsection Generating certificates for VNC
+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.
-The GNU TLS packages provides a command called @code{certtool} which can
-be used to generate certificates and keys in PEM format. At a minimum it
-is necessary to setup a certificate authority, and issue certificates to
-each server. If using certificates for authentication, then each client
-will also need to be issued a certificate. The recommendation is for the
-server to keep its certificates in either @code{/etc/pki/qemu} or for
-unprivileged users in @code{$HOME/.pki/qemu}.
+When using TLS, if username+password authentication is desired, then a
+reasonable configuration is
+
+@example
+mech_list: scram-sha-1
+sasldb_path: /etc/qemu/passwd.db
+@end example
+
+The @code{saslpasswd2} program can be used to populate the @code{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.
+
+
+@node network_tls
+@section 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 @code{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
+@code{/etc/pki/qemu} or for unprivileged users in @code{$HOME/.pki/qemu}.
@menu
-* vnc_generate_ca::
-* vnc_generate_server::
-* vnc_generate_client::
+* tls_generate_ca::
+* tls_generate_server::
+* tls_generate_client::
+* tls_creds_setup::
+* tls_psk::
@end menu
-@node vnc_generate_ca
-@subsubsection Setup the Certificate Authority
+@node tls_generate_ca
+@subsection 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
# certtool --generate-privkey > ca-key.pem
@end example
-A CA needs to have a public certificate. For simplicity it can be a self-signed
-certificate, or one issue by a commercial certificate issuing authority. To
-generate a self-signed certificate requires one core piece of information, the
-name of the organization.
-
+To generate a self-signed certificate requires one core piece of information,
+the name of the organization. A template file @code{ca.info} should be
+populated with the desired data to avoid having to deal with interactive
+prompts from certtool:
@example
# cat > ca.info <<EOF
cn = Name of your organization
--outfile ca-cert.pem
@end example
-The @code{ca-cert.pem} file should be copied to all servers and clients wishing to utilize
-TLS support in the VNC server. The @code{ca-key.pem} must not be disclosed/copied at all.
+The @code{ca} keyword in the template sets the v3 basic constraints extension
+to indicate this certificate is for a CA, while @code{cert_signing_key} sets
+the key usage extension to indicate this will be used for signing other keys.
+The generated @code{ca-cert.pem} file should be copied to all servers and
+clients wishing to utilize TLS support in the VNC server. The @code{ca-key.pem}
+must not be disclosed/copied anywhere except the host responsible for issuing
+certificates.
-@node vnc_generate_server
-@subsubsection Issuing server certificates
+@node tls_generate_server
+@subsection 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 piece of information for a server certificate is the hostname. This should
-be the fully qualified hostname that the client will connect with, since the client
-will typically also verify the hostname in the certificate. On the host holding the
-secure CA private key:
-
-@example
-# cat > server.info <<EOF
+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 @code{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 @code{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.
+
+@example
+# cat > server-hostNNN.info <<EOF
organization = Name of your organization
-cn = server.foo.example.com
+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-key.pem
+# 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-key.pem \
- --template server.info \
- --outfile server-cert.pem
+ --load-privkey server-hostNNN-key.pem \
+ --template server-hostNNN.info \
+ --outfile server-hostNNN-cert.pem
@end example
-The @code{server-key.pem} and @code{server-cert.pem} files should now be securely copied
-to the server for which they were generated. The @code{server-key.pem} is security
-sensitive and should be kept protected with file mode 0600 to prevent disclosure.
+The @code{dns_name} and @code{ip_address} fields in the template are setting
+the subject alt name extension data. The @code{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 @code{encryption_key} and @code{signing_key} keyword is the key usage
+extension to indicate this certificate is intended for usage in the data
+session.
+
+The @code{server-hostNNN-key.pem} and @code{server-hostNNN-cert.pem} files
+should now be securely copied to the server for which they were generated,
+and renamed to @code{server-key.pem} and @code{server-cert.pem} when added
+to the @code{/etc/pki/qemu} directory on the target host. The @code{server-key.pem}
+file is security sensitive and should be kept protected with file mode 0600
+to prevent disclosure.
-@node vnc_generate_client
-@subsubsection Issuing client certificates
+@node tls_generate_client
+@subsection 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.
-If the QEMU VNC server is to use the @code{x509verify} option to validate client
-certificates as its authentication mechanism, each client also needs to be issued
-a certificate. The client certificate contains enough metadata to uniquely identify
-the client, typically organization, state, city, building, etc. On the host holding
-the secure CA private key:
@example
-# cat > client.info <<EOF
+# cat > client-hostNNN.info <<EOF
country = GB
state = London
-locality = London
+locality = City Of London
organization = Name of your organization
-cn = client.foo.example.com
+cn = hostNNN.foo.example.com
tls_www_client
encryption_key
signing_key
EOF
-# certtool --generate-privkey > client-key.pem
+# 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-key.pem \
- --template client.info \
- --outfile client-cert.pem
+ --load-privkey client-hostNNN-key.pem \
+ --template client-hostNNN.info \
+ --outfile client-hostNNN-cert.pem
+@end example
+
+The subject alt name extension data is not required for clients, so the
+the @code{dns_name} and @code{ip_address} fields are not included.
+The @code{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 @code{encryption_key} and @code{signing_key} keyword
+is the key usage extension to indicate this certificate is intended for
+usage in the data session.
+
+The @code{client-hostNNN-key.pem} and @code{client-hostNNN-cert.pem} files
+should now be securely copied to the client for which they were generated,
+and renamed to @code{client-key.pem} and @code{client-cert.pem} when added
+to the @code{/etc/pki/qemu} directory on the target host. The @code{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.
+
+@example
+# 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
@end example
-The @code{client-key.pem} and @code{client-cert.pem} files should now be securely
-copied to the client for which they were generated.
+When copying the PEM files to the target host, save them twice,
+once as @code{server-cert.pem} and @code{server-key.pem}, and
+again as @code{client-cert.pem} and @code{client-key.pem}.
+@node tls_creds_setup
+@subsection TLS x509 credential configuration
-@node vnc_setup_sasl
+QEMU has a standard mechanism for loading x509 credentials that will be
+used for network services and clients. It requires specifying the
+@code{tls-creds-x509} class name to the @code{--object} command line
+argument for the system emulators. Each set of credentials loaded should
+be given a unique string identifier via the @code{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.
-@subsection Configuring SASL mechanisms
+When specifying the object, the @code{dir} parameters specifies which
+directory contains the credential files. This directory is expected to
+contain files with the names mentioned previously, @code{ca-cert.pem},
+@code{server-key.pem}, @code{server-cert.pem}, @code{client-key.pem}
+and @code{client-cert.pem} as appropriate. It is also possible to
+include a set of pre-generated Diffie-Hellman (DH) parameters in a file
+@code{dh-params.pem}, which can be created using the
+@code{certtool --generate-dh-params} command. If omitted, QEMU will
+dynamically generate DH parameters when loading the credentials.
-The following documentation assumes use of the Cyrus SASL implementation on a
-Linux host, but the principals should apply to any other SASL impl. 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.
+The @code{endpoint} parameter indicates whether the credentials will
+be used for a network client or server, and determines which PEM
+files are loaded.
-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.
+The @code{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.
-When not using TLS the recommended configuration is
+To load server credentials with client certificate validation
+enabled
@example
-mech_list: gssapi
-keytab: /etc/qemu/krb5.tab
+$QEMU -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=server
@end example
-This says to use the 'GSSAPI' mechanism with the Kerberos v5 protocol, with
-the server principal stored in /etc/qemu/krb5.tab. For this to work the
-administrator of your KDC must generate a Kerberos principal for the server,
-with a name of 'qemu/somehost.example.com@@EXAMPLE.COM' replacing
-'somehost.example.com' with the fully qualified host name of the machine
-running QEMU, and 'EXAMPLE.COM' with the Kerberos Realm.
+while to load client credentials use
-When using TLS, if username+password authentication is desired, then a
-reasonable configuration is
+@example
+$QEMU -object tls-creds-x509,id=tls0,dir=/etc/pki/qemu,endpoint=client
+@end example
+
+Network services which support TLS will all have a @code{tls-creds}
+parameter which expects the ID of the TLS credentials object. For
+example with VNC:
@example
-mech_list: scram-sha-1
-sasldb_path: /etc/qemu/passwd.db
+$QEMU -vnc 0.0.0.0:0,tls-creds=tls0
@end example
-The saslpasswd2 program can be used to populate the passwd.db file with
-accounts.
+@node tls_psk
+@subsection TLS Pre-Shared Keys (PSK)
-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.
+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 @code{psktool} program to generate a @code{keys.psk}
+file containing one or more usernames and random keys:
+
+@example
+mkdir -m 0700 /tmp/keys
+psktool -u rich -p /tmp/keys/keys.psk
+@end example
+
+TLS-enabled servers such as qemu-nbd can use this directory like so:
+
+@example
+qemu-nbd \
+ -t -x / \
+ --object tls-creds-psk,id=tls0,endpoint=server,dir=/tmp/keys \
+ --tls-creds tls0 \
+ image.qcow2
+@end example
+
+When connecting from a qemu-based client you must specify the
+directory containing @code{keys.psk} and an optional @var{username}
+(defaults to ``qemu''):
+
+@example
+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=/
+@end example
@node gdb_usage
@section GDB usage
@section System emulator command line arguments
-@subsection -no-kvm-pit-reinjection (since 1.3.0)
-
-The ``-no-kvm-pit-reinjection'' argument is now a
-synonym for setting ``-global kvm-pit.lost_tick_policy=discard''.
-
-@subsection -no-kvm-irqchip (since 1.3.0)
-
-The ``-no-kvm-irqchip'' argument is now a synonym for
-setting ``-machine kernel_irqchip=off''.
-
@subsection -no-kvm (since 1.3.0)
The ``-no-kvm'' argument is now a synonym for setting
(for embedded NICs). The new syntax allows different settings to be
provided per NIC.
-@subsection -net vlan (since 2.9.0)
-
-The ``-net vlan=NN'' argument was mostly used to attach separate
-network backends to different virtual NICs. This is the default
-behavior for ``-netdev'' and ``-nic''. You can connect multiple
-``-netdev'' and ``-nic'' devices to the same network using the
-"hubport" network backend, created with ``-netdev hubport,hubid=NN,...''
-and ``-nic hubport,hubid=NN''.
-
@subsection -drive cyls=...,heads=...,secs=...,trans=... (since 2.10.0)
The drive geometry arguments are replaced by the the geometry arguments
The @code{-startdate} option has been replaced by @code{-rtc base=@var{date}}.
-@section qemu-img command line arguments
+@subsection -virtioconsole (since 3.0.0)
+
+Option @option{-virtioconsole} has been replaced by
+@option{-device virtconsole}.
+
+@subsection -clock (since 3.0.0)
+
+The @code{-clock} option is ignored since QEMU version 1.7.0. There is no
+replacement since it is not needed anymore.
-@subsection convert -s (since 2.0.0)
+@subsection -enable-hax (since 3.0.0)
-The ``convert -s snapshot_id_or_name'' argument is obsoleted
-by the ``convert -l snapshot_param'' argument instead.
+The @option{-enable-hax} option has been replaced by @option{-accel hax}.
+Both options have been introduced in QEMU version 2.9.0.
+
+@subsection -drive file=json:@{...@{'driver':'file'@}@} (since 3.0)
+
+The 'file' driver for drives is no longer appropriate for character or host
+devices and will only accept regular files (S_IFREG). The correct driver
+for these file types is 'host_cdrom' or 'host_device' as appropriate.
@section QEMU Machine Protocol (QMP) commands
The ``query-cpus'' command is replaced by the ``query-cpus-fast'' command.
+@subsection query-cpus-fast "arch" output member (since 3.0.0)
+
+The ``arch'' output member of the ``query-cpus-fast'' command is
+replaced by the ``target'' output member.
+
@section System emulator devices
@subsection ivshmem (since 2.6.0)
@section System emulator machines
-@subsection Xilinx EP108 (since 2.11.0)
+@subsection pc-0.10 and pc-0.11 (since 3.0)
+
+These machine types are very old and likely can not be used for live migration
+from old QEMU versions anymore. A newer machine type should be used instead.
-The ``xlnx-ep108'' machine has been replaced by the ``xlnx-zcu102'' machine.
-The ``xlnx-zcu102'' machine has the same features and capabilites in QEMU.
+@section Device options
-@section Block device options
+@subsection Block device options
-@subsection "backing": "" (since 2.12.0)
+@subsubsection "backing": "" (since 2.12.0)
In order to prevent QEMU from automatically opening an image's backing
chain, use ``"backing": null'' instead.
+@subsection vio-spapr-device device options
+
+@subsubsection "irq": "" (since 3.0.0)
+
+The ``irq'' property is obsoleted.
+
+@node Supported build platforms
+@appendix 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 @url{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.
+
+@section 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. 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.
+
+@section Windows
+
+The project supports building with current versions of the MinGW toolchain,
+hosted on Linux.
+
+@section macOS
+
+The project supports building with the two most recent versions of macOS, with
+the current homebrew package set available.
+
+@section FreeBSD
+
+The project aims to support the all the versions which are not end of life.
+
+@section 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.
+
+@section OpenBSD
+
+The project aims to support the all the versions which are not end of life.
+
@node License
@appendix License
projects / mirror_qemu.git / blobdiff