docs/about/removed-features: Document removed CLI options from QEMU v3.1

These CLI options had been removed/replaced in QEMU v3.1. Still, some
people might want to update from older versions to the recent QEMU version,
so we should give some recommendations for the replacements in our
documentation.

Message-Id: <20210811084103.74832-4-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

docs/about/removed-features.rst

@@ -79,6 +79,73 @@ Use ``-machine kernel_irqchip=off`` instead.
 
 Use ``-global kvm-pit.lost_tick_policy=discard`` instead.
 
+``-balloon`` (removed in 3.1)
+'''''''''''''''''''''''''''''
+
+The ``-balloon virtio`` option has been replaced by ``-device virtio-balloon``.
+The ``-balloon none`` option was a no-op and has no replacement.
+
+``-bootp`` (removed in 3.1)
+'''''''''''''''''''''''''''
+
+The ``-bootp /some/file`` argument is replaced by either
+``-netdev user,id=x,bootp=/some/file`` (for pluggable NICs, accompanied with
+``-device ...,netdev=x``), or ``-nic user,bootp=/some/file`` (for on-board NICs).
+The new syntax allows different settings to be provided per NIC.
+
+``-redir`` (removed in 3.1)
+'''''''''''''''''''''''''''
+
+The ``-redir [tcp|udp]:hostport:[guestaddr]:guestport`` option is replaced
+by either ``-netdev
+user,id=x,hostfwd=[tcp|udp]:[hostaddr]:hostport-[guestaddr]:guestport``
+(for pluggable NICs, accompanied with ``-device ...,netdev=x``) or by the option
+``-nic user,hostfwd=[tcp|udp]:[hostaddr]:hostport-[guestaddr]:guestport``
+(for on-board NICs). The new syntax allows different settings to be provided
+per NIC.
+
+``-smb`` (removed in 3.1)
+'''''''''''''''''''''''''
+
+The ``-smb /some/dir`` argument is replaced by either
+``-netdev user,id=x,smb=/some/dir`` (for pluggable NICs, accompanied with
+``-device ...,netdev=x``), or ``-nic user,smb=/some/dir`` (for on-board NICs).
+The new syntax allows different settings to be provided per NIC.
+
+``-tftp`` (removed in 3.1)
+''''''''''''''''''''''''''
+
+The ``-tftp /some/dir`` argument is replaced by either
+``-netdev user,id=x,tftp=/some/dir`` (for pluggable NICs, accompanied with
+``-device ...,netdev=x``), or ``-nic user,tftp=/some/dir`` (for embedded NICs).
+The new syntax allows different settings to be provided per NIC.
+
+``-localtime`` (removed in 3.1)
+'''''''''''''''''''''''''''''''
+
+Replaced by ``-rtc base=localtime``.
+
+``-nodefconfig`` (removed in 3.1)
+'''''''''''''''''''''''''''''''''
+
+Use ``-no-user-config`` instead.
+
+``-rtc-td-hack`` (removed in 3.1)
+'''''''''''''''''''''''''''''''''
+
+Use ``-rtc driftfix=slew`` instead.
+
+``-startdate`` (removed in 3.1)
+'''''''''''''''''''''''''''''''
+
+Replaced by ``-rtc base=date``.
+
+``-vnc ...,tls=...``, ``-vnc ...,x509=...`` & ``-vnc ...,x509verify=...``
+'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
+
+The "tls-creds" option should be used instead to point to a "tls-creds-x509"
+object created using "-object".
+
 ``-net ...,name=...`` (removed in 5.1)
 ''''''''''''''''''''''''''''''''''''''