Features/LegacyRemoval

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Revision as of 09:35, 2 May 2017 by Huth (talk | contribs) (Add some more legacy options)

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 channel Replaced by "-netdev user,guestfwd=..."

(and is even not documented, i.e. hardly used in the wild)

v2.6.0 v3.0.0
-net dump Replaced by "-object filter-dump,..." v2.10.0 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
-hdachs Replaced by options on "-device" v2.10.0 v3.0.0
-drive boot= Dummy legacy option from qemu-kvm v1.3.0 v3.0.0
-no-kvm-pit Dummy legacy option from qemu-kvm v1.3.0 v3.0.0
-no-kvm-pit-reinjection Legacy option from qemu-kvm v1.3.0 v3.0.0
-tdf Dummy legacy option from qemu-kvm v1.3.0 v3.0.0
-drive media=
-drive serial=
-drive trans=
-drive secs=
-drive heads=
-drive cyls=
-drive addr=
Replaced by options on "-device". up to v1.2.0 v3.0.0 ?
-no-kvm Not necessary anymore, TCG is default not yet ?

Future candidates

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 ?
-usbdevice Replaced by the generic -device parameter not yet ?
-drive Replaced by "-blockdev" and "-device". Need to check that all devices automatically created by machines are still configurable. not yet ?
-enable-kvm Use "-M accel=kvm" instead not yet ?
-enable-hax Use "-M accel=hax" instead not yet ?

Deprecated qemu-img parameters

Parameter Rationale Deprecated in Removal in
snapshot_id_or_name Use snapshot_param instead v2.0.0 ?
-e -o encryption v0.14 v3.0.0 ?
-6 -o compat6 v0.14 v3.0.0 ?

Deprecated HMP commands

Command Rationale Deprecated in Removal in
usb_add, usb_remove Replaced by "device_add" and "device_del" not yet v3.0.0 ?
host_net_add, host_net_remove Replaced by "netdev_add" and "netdev_del" not yet v3.0.0 ?

Future candidates

Parameter Rationale Deprecated in Removal in
migrate_set_downtime, migrate_set_speed Replaced by "migrate_set_parameter" 2.8 ?

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 (but firmware code paths would be different, do we care?) not yet ?
pc-0.10 and pc-0.11 Oldest QEMU version that is likely still used in the wild is 0.12 (CentOS 6) 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 ?
scsi-disk Replaced by "scsi-cd" and "scsi-hd" v0.15.0 v3.0.0 ?
isa-vga unused when isapc machine type goes away not yet ?
isa-cirrus-vga unused when isapc machine type goes away not yet ?
ne2k_isa unused when isapc machine type goes away not yet ?

Alternatively: drop media=cdrom, make ide-hd and scsi-hd synonyms for ide-disk and scsi-disk.

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?