qemu-deprecated.texi

   1 @node Deprecated features
   2 @appendix Deprecated features
   3
   4 In general features are intended to be supported indefinitely once
   5 introduced into QEMU. In the event that a feature needs to be removed,
   6 it will be listed in this appendix. The feature will remain functional
   7 for 2 releases prior to actual removal. Deprecated features may also
   8 generate warnings on the console when QEMU starts up, or if activated
   9 via a monitor command, however, this is not a mandatory requirement.
  10
  11 Prior to the 2.10.0 release there was no official policy on how
  12 long features would be deprecated prior to their removal, nor
  13 any documented list of which features were deprecated. Thus
  14 any features deprecated prior to 2.10.0 will be treated as if
  15 they were first deprecated in the 2.10.0 release.
  16
  17 What follows is a list of all features currently marked as
  18 deprecated.
  19
  20 @section System emulator command line arguments
  21
  22 @subsection -machine enforce-config-section=on|off (since 3.1)
  23
  24 The @option{enforce-config-section} parameter is replaced by the
  25 @option{-global migration.send-configuration=@var{on|off}} option.
  26
  27 @subsection -no-kvm (since 1.3.0)
  28
  29 The ``-no-kvm'' argument is now a synonym for setting
  30 ``-machine accel=tcg''.
  31
  32 @subsection -usbdevice (since 2.10.0)
  33
  34 The ``-usbdevice DEV'' argument is now a synonym for setting
  35 the ``-device usb-DEV'' argument instead. The deprecated syntax
  36 would automatically enable USB support on the machine type.
  37 If using the new syntax, USB support must be explicitly
  38 enabled via the ``-machine usb=on'' argument.
  39
  40 @subsection -drive file=json:@{...@{'driver':'file'@}@} (since 3.0)
  41
  42 The 'file' driver for drives is no longer appropriate for character or host
  43 devices and will only accept regular files (S_IFREG). The correct driver
  44 for these file types is 'host_cdrom' or 'host_device' as appropriate.
  45
  46 @subsection -net ...,name=@var{name} (since 3.1)
  47
  48 The @option{name} parameter of the @option{-net} option is a synonym
  49 for the @option{id} parameter, which should now be used instead.
  50
  51 @subsection -smp (invalid topologies) (since 3.1)
  52
  53 CPU topology properties should describe whole machine topology including
  54 possible CPUs.
  55
  56 However, historically it was possible to start QEMU with an incorrect topology
  57 where @math{@var{n} <= @var{sockets} * @var{cores} * @var{threads} < @var{maxcpus}},
  58 which could lead to an incorrect topology enumeration by the guest.
  59 Support for invalid topologies will be removed, the user must ensure
  60 topologies described with -smp include all possible cpus, i.e.
  61   @math{@var{sockets} * @var{cores} * @var{threads} = @var{maxcpus}}.
  62
  63 @section QEMU Machine Protocol (QMP) commands
  64
  65 @subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0)
  66
  67 "autoload" parameter is now ignored. All bitmaps are automatically loaded
  68 from qcow2 images.
  69
  70 @subsection query-cpus (since 2.12.0)
  71
  72 The ``query-cpus'' command is replaced by the ``query-cpus-fast'' command.
  73
  74 @subsection query-cpus-fast "arch" output member (since 3.0.0)
  75
  76 The ``arch'' output member of the ``query-cpus-fast'' command is
  77 replaced by the ``target'' output member.
  78
  79 @subsection cpu-add (since 4.0)
  80
  81 Use ``device_add'' for hotplugging vCPUs instead of ``cpu-add''.  See
  82 documentation of ``query-hotpluggable-cpus'' for additional
  83 details.
  84
  85 @subsection query-events (since 4.0)
  86
  87 The ``query-events'' command has been superseded by the more powerful
  88 and accurate ``query-qmp-schema'' command.
  89
  90 @section Human Monitor Protocol (HMP) commands
  91
  92 @subsection The hub_id parameter of 'hostfwd_add' / 'hostfwd_remove' (since 3.1)
  93
  94 The @option{[hub_id name]} parameter tuple of the 'hostfwd_add' and
  95 'hostfwd_remove' HMP commands has been replaced by @option{netdev_id}.
  96
  97 @subsection cpu-add (since 4.0)
  98
  99 Use ``device_add'' for hotplugging vCPUs instead of ``cpu-add''.  See
 100 documentation of ``query-hotpluggable-cpus'' for additional details.
 101
 102 @section System emulator devices
 103
 104 @subsection bluetooth (since 3.1)
 105
 106 The bluetooth subsystem is unmaintained since many years and likely bitrotten
 107 quite a bit. It will be removed without replacement unless some users speaks
 108 up at the @email{qemu-devel@@nongnu.org} mailing list with information about
 109 their usecases.
 110
 111 @section System emulator machines
 112
 113 @subsection pc-0.12, pc-0.13, pc-0.14 and pc-0.15 (since 4.0)
 114
 115 These machine types are very old and likely can not be used for live migration
 116 from old QEMU versions anymore. A newer machine type should be used instead.
 117
 118 @subsection prep (PowerPC) (since 3.1)
 119
 120 This machine type uses an unmaintained firmware, broken in lots of ways,
 121 and unable to start post-2004 operating systems. 40p machine type should be
 122 used instead.
 123
 124 @section Device options
 125
 126 @subsection Block device options
 127
 128 @subsubsection "backing": "" (since 2.12.0)
 129
 130 In order to prevent QEMU from automatically opening an image's backing
 131 chain, use ``"backing": null'' instead.
 132
 133 @subsubsection rbd keyvalue pair encoded filenames: "" (since 3.1.0)
 134
 135 Options for ``rbd'' should be specified according to its runtime options,
 136 like other block drivers.  Legacy parsing of keyvalue pair encoded
 137 filenames is useful to open images with the old format for backing files;
 138 These image files should be updated to use the current format.
 139
 140 Example of legacy encoding:
 141
 142 @code{json:@{"file.driver":"rbd", "file.filename":"rbd:rbd/name"@}}
 143
 144 The above, converted to the current supported format:
 145
 146 @code{json:@{"file.driver":"rbd", "file.pool":"rbd", "file.image":"name"@}}
 147
 148 @section Related binaries
 149
 150 @subsection qemu-nbd --partition (since 4.0.0)
 151
 152 The ``qemu-nbd --partition $digit'' code (also spelled @option{-P})
 153 can only handle MBR partitions, and has never correctly handled
 154 logical partitions beyond partition 5.  If you know the offset and
 155 length of the partition (perhaps by using @code{sfdisk} within the
 156 guest), you can achieve the effect of exporting just that subset of
 157 the disk by use of the @option{--image-opts} option with a raw
 158 blockdev using the @code{offset} and @code{size} parameters layered on
 159 top of any other existing blockdev. For example, if partition 1 is
 160 100MiB long starting at 1MiB, the old command:
 161
 162 @code{qemu-nbd -t -P 1 -f qcow2 file.qcow2}
 163
 164 can be rewritten as:
 165
 166 @code{qemu-nbd -t --image-opts driver=raw,offset=1M,size=100M,file.driver=qcow2,file.backing.driver=file,file.backing.filename=file.qcow2}
 167
 168 Alternatively, the @code{nbdkit} project provides a more powerful
 169 partition filter on top of its nbd plugin, which can be used to select
 170 an arbitrary MBR or GPT partition on top of any other full-image NBD
 171 export.  Using this to rewrite the above example results in:
 172
 173 @code{qemu-nbd -t -k /tmp/sock -f qcow2 file.qcow2 &}
 174 @code{nbdkit -f --filter=partition nbd socket=/tmp/sock partition=1}
 175
 176 Note that if you are exposing the export via /dev/nbd0, it is easier
 177 to just export the entire image and then mount only /dev/nbd0p1 than
 178 it is to reinvoke @command{qemu-nbd -c /dev/nbd0} limited to just a
 179 subset of the image.