Features/LegacyRemoval: Difference between revisions

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=== Problem description ===
QEMU has a lot of interfaces (like command line options or HMP commands) and old features (like certain machine types) which are considered as deprecated since other more generic interfaces/features have been established instead. We cannot carry the old code around forever. But we also do not want to remove it immediately to give the users and upper layer software stacks (like libvirt) a chance to migrate to the new interfaces step by step.


QEMU has a lot of interfaces (like command line options or HMP commands) and old features (like certain machine types) which are considered as deprecated since other more generic interfaces/features have been established instead. We likely don't want to carry the old code around forever. But we also do not want to remove it immediately to give the users and upper layer software stacks (like libvirt) a chance to migrate to the new interfaces step by step. So this page is about collecting information and ideas about which interfaces/features are considered as obsolete and when they should be removed.
This page was used to gather ideas about such deprecated features and interfaces, which finally culminated in the official deprecation chapter of the QEMU documentation. Since this page here was quickly out of date afterwards, its content has been removed now. Please visit https://qemu-project.gitlab.io/qemu/about/deprecated.html for the current official list instead.


=== Rules for removing an interface ===
For information about features that have already been removed, please consult the https://qemu-project.gitlab.io/qemu/about/removed-features.html page.
 
Before an interface can be removed, there needs to be a clear transition plan for doing so. This means it should be added to this wiki page, and that there have to be at least two public releases of QEMU where the interface still works, but issues a warning when used. Two public releases are required so that the users have at least one development cycle to complain if they think that there is a good reason that the interface should <em>not</em> be removed. The warning should say that the interface is deprecated / going away soon, with a pointer to documentation or similar information about its replacement syntax.
 
== Deprecated command line parameters ==
 
{| class="wikitable" border="1"
!  Parameter
!  Rationale
!  Deprecated in
!  Removal in
|-
| -net channel
| Replaced by "-netdev user,guestfwd=..."
(and is even not documented, i.e. hardly used in the wild)
| v2.6.0
| v3.0.0
|-
| -smb
| Replaced by "-netdev user,smb=..."
| v2.6.0
| v3.0.0 ?
|-
| -tftp
| Replaced by "-netdev user,tftp=..."
| v2.6.0
| v3.0.0 ?
|-
| -bootp
| Replaced by "-netdev user,bootfile=..."
| v2.6.0
| v3.0.0 ?
|-
| -redir
| Replaced by "-netdev user,hostfwd=..."
| v2.6.0
| v3.0.0 ?
|-
| -usbdevice
| Replaced by the generic -device parameter
| not yet
| ?
|}
 
== Deprecated HMP commands ==
 
{| class="wikitable" border="1"
!  Command
!  Rationale
!  Deprecated in
!  Removal in
|-
| host_net_add
| Replaced by "netdev_add"
| not yet
| ?
|-
| host_net_remove
| Replaced by "netdev_del"
| not yet
| ?
|}
 
== Deprecated machines ==
 
{| class="wikitable" border="1"
!  Machine
!  Rationale
!  Deprecated in
!  Removal in
|-
| prep (ppc)
| Obsoleted by the "40p" machine
| not yet
| ?
|-
|}

Latest revision as of 10:45, 4 August 2021

QEMU has a lot of interfaces (like command line options or HMP commands) and old features (like certain machine types) which are considered as deprecated since other more generic interfaces/features have been established instead. We cannot carry the old code around forever. But we also do not want to remove it immediately to give the users and upper layer software stacks (like libvirt) a chance to migrate to the new interfaces step by step.

This page was used to gather ideas about such deprecated features and interfaces, which finally culminated in the official deprecation chapter of the QEMU documentation. Since this page here was quickly out of date afterwards, its content has been removed now. Please visit https://qemu-project.gitlab.io/qemu/about/deprecated.html for the current official list instead.

For information about features that have already been removed, please consult the https://qemu-project.gitlab.io/qemu/about/removed-features.html page.

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