Merge remote-tracking branch 'remotes/armbru/tags/pull-yank-2021-01-13' into staging

Yank patches patches for 2021-01-13

# gpg: Signature made Wed 13 Jan 2021 09:25:46 GMT
# gpg:                using RSA key 354BC8B3D7EB2A6B68674E5F3870B400EB918653
# gpg:                issuer "armbru@redhat.com"
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>" [full]
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>" [full]
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-yank-2021-01-13:
  tests/test-char.c: Wait for the chardev to connect in char_socket_client_dupid_test
  io: Document qmp oob suitability of qio_channel_shutdown and io_shutdown
  io/channel-tls.c: make qio_channel_tls_shutdown thread-safe
  migration: Add yank feature
  chardev/char-socket.c: Add yank feature
  block/nbd.c: Add yank feature
  Introduce yank feature

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

3 files changed, 121 insertions, 0 deletions

diff --git a/qapi/meson.build b/qapi/meson.build
index 0e98146f1f..ab68e7900e 100644
--- a/qapi/meson.build
+++ b/qapi/meson.build
@@ -47,6 +47,7 @@ qapi_all_modules = [
   'trace',
   'transaction',
   'ui',
+  'yank',
 ]
 
 qapi_storage_daemon_modules = [
diff --git a/qapi/qapi-schema.json b/qapi/qapi-schema.json
index 0b444b76d2..3441c9a9ae 100644
--- a/qapi/qapi-schema.json
+++ b/qapi/qapi-schema.json
@@ -86,6 +86,7 @@
 { 'include': 'machine.json' }
 { 'include': 'machine-target.json' }
 { 'include': 'replay.json' }
+{ 'include': 'yank.json' }
 { 'include': 'misc.json' }
 { 'include': 'misc-target.json' }
 { 'include': 'audio.json' }
diff --git a/qapi/yank.json b/qapi/yank.json
new file mode 100644
index 0000000000..167a775594
--- /dev/null
+++ b/qapi/yank.json
@@ -0,0 +1,119 @@
+# -*- Mode: Python -*-
+# vim: filetype=python
+#
+
+##
+# = Yank feature
+##
+
+##
+# @YankInstanceType:
+#
+# An enumeration of yank instance types. See @YankInstance for more
+# information.
+#
+# Since: 6.0
+##
+{ 'enum': 'YankInstanceType',
+  'data': [ 'block-node', 'chardev', 'migration' ] }
+
+##
+# @YankInstanceBlockNode:
+#
+# Specifies which block graph node to yank. See @YankInstance for more
+# information.
+#
+# @node-name: the name of the block graph node
+#
+# Since: 6.0
+##
+{ 'struct': 'YankInstanceBlockNode',
+  'data': { 'node-name': 'str' } }
+
+##
+# @YankInstanceChardev:
+#
+# Specifies which character device to yank. See @YankInstance for more
+# information.
+#
+# @id: the chardev's ID
+#
+# Since: 6.0
+##
+{ 'struct': 'YankInstanceChardev',
+  'data': { 'id': 'str' } }
+
+##
+# @YankInstance:
+#
+# A yank instance can be yanked with the @yank qmp command to recover from a
+# hanging QEMU.
+#
+# Currently implemented yank instances:
+#  - nbd block device:
+#    Yanking it will shut down the connection to the nbd server without
+#    attempting to reconnect.
+#  - socket chardev:
+#    Yanking it will shut down the connected socket.
+#  - migration:
+#    Yanking it will shut down all migration connections. Unlike
+#    @migrate_cancel, it will not notify the migration process, so migration
+#    will go into @failed state, instead of @cancelled state. @yank should be
+#    used to recover from hangs.
+#
+# Since: 6.0
+##
+{ 'union': 'YankInstance',
+  'base': { 'type': 'YankInstanceType' },
+  'discriminator': 'type',
+  'data': {
+      'block-node': 'YankInstanceBlockNode',
+      'chardev': 'YankInstanceChardev' } }
+
+##
+# @yank:
+#
+# Try to recover from hanging QEMU by yanking the specified instances. See
+# @YankInstance for more information.
+#
+# Takes a list of @YankInstance as argument.
+#
+# Returns: - Nothing on success
+#          - @DeviceNotFound error, if any of the YankInstances doesn't exist
+#
+# Example:
+#
+# -> { "execute": "yank",
+#      "arguments": {
+#          "instances": [
+#               { "type": "block-node",
+#                 "node-name": "nbd0" }
+#          ] } }
+# <- { "return": {} }
+#
+# Since: 6.0
+##
+{ 'command': 'yank',
+  'data': { 'instances': ['YankInstance'] },
+  'allow-oob': true }
+
+##
+# @query-yank:
+#
+# Query yank instances. See @YankInstance for more information.
+#
+# Returns: list of @YankInstance
+#
+# Example:
+#
+# -> { "execute": "query-yank" }
+# <- { "return": [
+#          { "type": "block-node",
+#            "node-name": "nbd0" }
+#      ] }
+#
+# Since: 6.0
+##
+{ 'command': 'query-yank',
+  'returns': ['YankInstance'],
+  'allow-oob': true }