On 09/02/23 1:47 am, Eric Blake wrote:
On Wed, Feb 08, 2023 at 09:35:56AM +0000, Het Gala wrote:
Existing 'migrate' QAPI design enforces transport mechanism, ip address
of destination interface and corresponding port number in the form
of a unified string 'uri' parameter for initiating a migration stream.
This scheme has a significant flaw in it - double encoding of existing
URIs to extract migration info.
+##
+# @MigrateTransport:
+#
+# The supported communication transport mechanisms for migration
+#
+# @socket: Supported communication type between two devices for migration.
+# Socket is able to cover all of 'tcp', 'unix', 'vsock' and
+# 'fd' already
+#
+# @exec: Supported communication type to redirect migration stream into file.
+#
+# @rdma: Supported communication type to redirect rdma type migration stream.
+#
+# Since 8.0
+##
+{ 'enum': 'MigrateTransport',
+ 'data': ['socket', 'exec', 'rdma'] }
+
+##
+# @MigrateSocketAddr:
+#
+# To support different type of socket.
+#
+# @socket-type: Different type of socket connections.
+#
+# Since 8.0
+##
+{ 'struct': 'MigrateSocketAddr',
+ 'data': {'socket-type': 'SocketAddress' } }
Here, you use 'socket-type',...
Yes, I wanted a suggestion here actually. Will 'data' instead of
'socket-type' be the right fit ? It will also be consistent with exec
and rdma if changed to 'data'.
+
+##
+# @MigrateExecAddr:
+ #
+ # Since 8.0
+ ##
+{ 'struct': 'MigrateExecAddr',
+ 'data' : {'data': ['str'] } }
Inconsistent on whether you have a space before :. Most of our qapi
files prefer the layout:
'key': 'value'
that is, no space before, one space after. It doesn't affect
correctness, but a consistent visual style is worth striving for.
Okay, thanks Eric for pointing it out. Will make sure I follow this
going forward.
+
+##
+# @MigrateRdmaAddr:
+#
+# Since 8.0
+##
+{ 'struct': 'MigrateRdmaAddr',
+ 'data' : {'data': 'InetSocketAddress' } }
...while these branches supply everything else under 'data'. Also,
while you documented @socket-type above, you did not document @data in
either of these two types. [1]
Ack. In that case, I feel it would be better if I change from
'socket-type' to 'data' to keep consistency among the QAPI.
+
+##
+# @MigrateAddress:
+#
+# The options available for communication transport mechanisms for migration
+#
+# Since 8.0
+##
+{ 'union' : 'MigrateAddress',
+ 'base' : { 'transport' : 'MigrateTransport'},
+ 'discriminator' : 'transport',
+ 'data' : {
+ 'socket' : 'MigrateSocketAddr',
+ 'exec' : 'MigrateExecAddr',
+ 'rdma': 'MigrateRdmaAddr' } }
Another example of inconsistent spacing around :.
I'm guessing the reason you didn't go with 'socket': 'SocketAddress'
is that SocketAddress is itself a discriminated union, and Markus does
not yet have the QAPI generator wired up to support one union as a
branch of another larger union? It leads to extra nesting on the wire
[2]
Yes Eric. I did search if it is possible for a union inside a branch of
union. That's the reason, I had to choose this path for 'socket' and
'rdma', and to keep consistency, I did the same with 'exec' too.
+
+##
+# @MigrateChannelType:
+#
+# The supported options for migration channel type requests
+#
+# @main: Support request for main outbound migration control channel
+#
+# Since 8.0
+##
+{ 'enum': 'MigrateChannelType',
+ 'data': [ 'main'] }
A different spacing issue: most arrays in QAPI either have spaces at
both ends (as in [ 'string' ]) or neither (as in ['string']). Here,
it looks lopsided with space at the front but not the back.
Ack Eric. Thanks for pointing it out. Will take care about this small
issues from next time.
+
+##
+# @MigrateChannel:
+#
+# Information regarding migration Channel-type for transferring packets,
+# source and corresponding destination interface for socket connection
+# and number of multifd channels over the interface.
+#
+# @channeltype: Name of Channel type for transfering packet information
+#
+# @addr: SocketAddress of destination interface
More than just a SocketAddress, per the discriminated union type defined above.
Yes, infact one of the branches MigrateChannel. Ack.
+#
+# Since 8.0
+##
+{ 'struct': 'MigrateChannel',
+ 'data' : {
+ 'channeltype' : 'MigrateChannelType',
+ 'addr' : 'MigrateAddress' } }
+
##
# @migrate:
#
# Migrates the current running guest to another Virtual Machine.
#
# @uri: the Uniform Resource Identifier of the destination VM
+# for migration thread
+#
+# @channel: Struct containing migration channel type, along with all
+# the details of destination interface required for initiating
+# a migration stream.
#
# @blk: do block migration (full disk copy)
#
@@ -1479,15 +1575,46 @@
# 3. The user Monitor's "detach" argument is invalid in QMP and should not
# be used
#
+# 4. The uri argument should have the Uniform Resource Identifier of default
+# destination VM. This connection will be bound to default network
+#
+# 5. Both 'uri' and 'channel' arguments, are mutually exclusive but, at least
+# one of the two arguments should be present.
Grammar suggestion:
'uri' and 'channel' are mutually exclusive; exactly one of the two
should be present.
Ack.
+#
# Example:
#
# -> { "execute": "migrate", "arguments": { "uri": "tcp:0:4446" } }
# <- { "return": {} }
#
+# -> { "execute": "migrate",
+# "arguments": {
+# "channel": { "channeltype": "main",
+# "addr": { "transport": "socket",
+# "socket-type": { "type': "inet',
+# "host": "10.12.34.9",
+# "port": "1050" } } } } }
[2] This is the extra nesting that occurs because of the
'socket-type':'MigrateSocketAddr' above; getting rid of the nesting
would require 'socket-type':'SocketAddress', but QAPI would need to
support that first.
Yes Eric, excatly.
+# <- { "return": {} }
+#
+# -> { "execute": "migrate",
+# "arguments": {
+# "channel": { "channeltype": "main",
+# "addr": { "transport": "exec",
+# "exec": ["/bin/nc", "-U",
+# "/some/sock" ] } } } }
Another lopsided spacing in [].
Ack.
+# <- { "return": {} }
+#
+# -> { "execute": "migrate",
+# "arguments": {
+# "channel": { "channeltype": "main",
+# "addr": { "transport": "rdma",
+# "rdma": { "host": "10.12.34.9",
+# "port": "1050" } } } } }
[1] These examples look wrong; above, the schema named the nesting as 'data',
rather than 'exec' or 'rdma'.
Yes, instead of 'rdma' or 'exec', it should be replaced by 'data' here
in the examples. Ack.
+# <- { "return": {} }
+#
##
{ 'command': 'migrate',
- 'data': {'uri': 'str', '*blk': 'bool', '*inc': 'bool',
- '*detach': 'bool', '*resume': 'bool' } }
+ 'data': {'*uri': 'str', '*channel': 'MigrateChannel', '*blk': 'bool',
+ '*inc': 'bool', '*detach': 'bool', '*resume': 'bool' } }
But overall, I'm a fan of using a more type-accurate description of
the channel than the open-coded 'uri':'str'.
Yes, 'uri':'str' is kept for backward compatibility right now. This will
be depricated in later stages.
Regards,
Het Gala.
