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hmp: Add support for coroutine command handlers

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Often, QMP command handlers are not only called to handle QMP commands,
but also from a corresponding HMP command handler. In order to give them
a consistent environment, optionally run HMP command handlers in a
coroutine, too.

The implementation is a lot simpler than in QMP because for HMP, we
still block the VM while the coroutine is running.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20201005155855.256490-11-kwolf@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
This commit is contained in:
Kevin Wolf 2020-10-05 17:58:51 +02:00 committed by Markus Armbruster
parent 9ce44e2ce2
commit bb4b9ead95
3 changed files with 35 additions and 7 deletions
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4
docs/devel/qapi-code-gen.txt
View file

@ -617,8 +617,8 @@ pitfalls are:
Since the command handler may assume coroutine context, any callers
other than the QMP dispatcher must also call it in coroutine context.
In particular, HMP commands calling such a QMP command handler must
enter coroutine context before calling the handler.
In particular, HMP commands calling such a QMP command handler must be
marked .coroutine = true in hmp-commands.hx.
It is an error to specify both 'coroutine': true and 'allow-oob': true
for a command. We don't currently have a use case for both together and

37
monitor/hmp.c
View file

@ -1056,12 +1056,26 @@ fail:
return NULL;
}
typedef struct HandleHmpCommandCo {
Monitor *mon;
const HMPCommand *cmd;
QDict *qdict;
bool done;
} HandleHmpCommandCo;
static void handle_hmp_command_co(void *opaque)
{
HandleHmpCommandCo *data = opaque;
data->cmd->cmd(data->mon, data->qdict);
monitor_set_cur(qemu_coroutine_self(), NULL);
data->done = true;
}
void handle_hmp_command(MonitorHMP *mon, const char *cmdline)
{
QDict *qdict;
const HMPCommand *cmd;
const char *cmd_start = cmdline;
Monitor *old_mon;
trace_handle_hmp_command(mon, cmdline);
@ -1080,10 +1094,23 @@ void handle_hmp_command(MonitorHMP *mon, const char *cmdline)
return;
}
/* old_mon is non-NULL when called from qmp_human_monitor_command() */
old_mon = monitor_set_cur(qemu_coroutine_self(), &mon->common);
cmd->cmd(&mon->common, qdict);
monitor_set_cur(qemu_coroutine_self(), old_mon);
if (!cmd->coroutine) {
/* old_mon is non-NULL when called from qmp_human_monitor_command() */
Monitor *old_mon = monitor_set_cur(qemu_coroutine_self(), &mon->common);
cmd->cmd(&mon->common, qdict);
monitor_set_cur(qemu_coroutine_self(), old_mon);
} else {
HandleHmpCommandCo data = {
.mon = &mon->common,
.cmd = cmd,
.qdict = qdict,
.done = false,
};
Coroutine *co = qemu_coroutine_create(handle_hmp_command_co, &data);
monitor_set_cur(co, &mon->common);
aio_co_enter(qemu_get_aio_context(), co);
AIO_WAIT_WHILE(qemu_get_aio_context(), !data.done);
}
qobject_unref(qdict);
}

1
monitor/monitor-internal.h
View file

@ -74,6 +74,7 @@ typedef struct HMPCommand {
const char *help;
const char *flags; /* p=preconfig */
void (*cmd)(Monitor *mon, const QDict *qdict);
bool coroutine;
/*
* @sub_table is a list of 2nd level of commands. If it does not exist,
* cmd should be used. If it exists, sub_table[?].cmd should be