Het Gala <het.g...@nutanix.com> writes:
> This patch introduces well defined MigrateAddress struct and its related
> child objects.
>
> The existing argument of 'migrate' and 'migrate-incoming' QAPI - 'uri'
> is of string type. The current migration flow follows double encoding
> scheme for fetching migration parameters such as 'uri' and this is
> not an ideal design.
>
> Motive for intoducing struct level design is to prevent double encoding
> of QAPI arguments, as Qemu should be able to directly use the QAPI
> arguments without any level of encoding.
>
> Suggested-by: Aravind Retnakaran <aravind.retnaka...@nutanix.com>
> Signed-off-by: Het Gala <het.g...@nutanix.com>
> Reviewed-by: Juan Quintela <quint...@redhat.com>
> Reviewed-by: Daniel P. Berrangé <berra...@redhat.com>
> ---
> qapi/migration.json | 45 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 45 insertions(+)
>
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 179af0c4d8..e61d25eba2 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -1407,6 +1407,51 @@
> ##
> { 'command': 'migrate-continue', 'data': {'state': 'MigrationStatus'} }
>
> +##
> +# @MigrationAddressType:
> +#
> +# The migration stream transport mechanisms.
> +#
> +# @socket: Migrate via socket.
> +#
> +# @exec: Direct the migration stream to another process.
> +#
> +# @rdma: Migrate via RDMA.
> +#
> +# Since 8.1
> +##
> +{ 'enum': 'MigrationAddressType',
> + 'data': ['socket', 'exec', 'rdma'] }
> +
> +##
> +# @MigrationExecCommand:
> +#
> +# @args: list of commands for migraton stream execution to a file.
Typo: migration
> +#
> +# Notes:
> +#
> +# 1. @args[0] needs to be the path to the new program.
@args can't be a "list of commands", as we're spawning just one process.
So what is it?
Digging through the code with the entire series applied... Member @args
is used in two places:
1. qemu_start_incoming_migration() passes it to
exec_start_incoming_migration(), which translates it into an array
and passes it to qio_channel_command_new_spawn().
2. qmp_migrate() passes it to exec_start_outgoing_migration(), which
does the same.
qio_channel_command_new_spawn() passes it to
g_spawn_async_with_pipes(). A close read of the latter's documentation
leads me to:
* args[0] is the excutable's file name. As usual, a relative name is
relative to the QEMU process's current working directory.
* args[1..] are the arguments.
Unlike POSIX interfaces like execv() and posix_spawn(), this doesn't
separate the executable's file name and 0-th argument.
In short, the head of @args is the executable's filename, and the
remainder are the arguments. The fact that the the executable's
filename is passed as 0-th argument to the child process is detail.
Perhaps this could do:
##
# @MigrationExecCommand:
#
# @args: command and arguments to execute.
If we want more detail, perhaps:
# @args: command (list head) and arguments (list tail) to execute.
Not sure we need it. Thoughts?
> +#
> +# Since 8.1
> +##
> +{ 'struct': 'MigrationExecCommand',
> + 'data': {'args': [ 'str' ] } }
> +
> +##
> +# @MigrationAddress:
> +#
> +# Migration endpoint configuration.
> +#
> +# Since 8.1
> +##
> +{ 'union': 'MigrationAddress',
> + 'base': { 'transport' : 'MigrationAddressType'},
> + 'discriminator': 'transport',
> + 'data': {
> + 'socket': 'SocketAddress',
> + 'exec': 'MigrationExecCommand',
> + 'rdma': 'InetSocketAddress' } }
> +
> ##
> # @migrate:
> #
