Features/LegacyRemoval

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 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.

Rules for removing an interface

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 not 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

Parameter	Rationale	Deprecated in	Removal in
-net	Replaced by "-netdev id=netdev0 -device e1000,netdev=netdev0". There are several loose ends: what about machine type built-in NICs that use nd_table[]? Can vlan command-line options be removed in some places?	not yet	v3.0.0 ?
-net dump	Replaced by "-object filter-dump,..."	not yet	v3.0.0 ?
-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

Command	Rationale	Deprecated in	Removal in
host_net_add, host_net_remove	Replaced by "netdev_add" and "netdev_del"	not yet	?
migrate_set_downtime, migrate_set_speed	Replaced by "migrate_set_parameter"	2.8	?
usb_add, usb_remove	Replaced by "device_add" and "device_del"	not yet	?

Deprecated machines

Machine	Rationale	Deprecated in	Removal in
prep (ppc)	Obsoleted by the "40p" machine	not yet	?
isapc (x86)	guests should be able to use "pc" instead	not yet	?

Deprecated devices

Device	Rationale	Deprecated in	Removal in
spapr-pci-vfio-host-bridge	See commit 72700d7e733948fa	v2.6.0	?
ide-device	Replaced by "ide-cd" and "ide-hd."	v0.15.0	?? v3.0.0 ??

Miscellaneous

• Should we deprecate support for AIX and Solaris as host OS? (there is no build machine available for those)
• Should we deprecate the ia64 TCG backend?