For some scenarios, we'd like to hot-add a monitor device. But QEMU
doesn't support that, yet. It does support hot-swapping character
backends with QMP command chardev-change. This lets us pre-add a
monitor with a null character backend, then chardev-change to a
socket backend. Except the chardev-change fails with "Chardev user
does not support chardev hotswap" because monitors don't provide the
required callback. Implement it for QMP monitors.
Signed-off-by: Li Zhang <li.zh...@ionos.com>
---
v3 -> v2:
* Rework the patch which is to add hotswap for QMP device
https://lists.nongnu.org/archive/html/qemu-devel/2021-04/msg03167.html
* Refactor the functions qmp_chardev_add and qmp_chardev_change
monitor/monitor-internal.h | 1 +
monitor/monitor.c | 4 +-
monitor/qmp.c | 84 +++++++++++++++++++++++++++-----------
3 files changed, 63 insertions(+), 26 deletions(-)
diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h
index 9c3a09cb01..162f73119b 100644
--- a/monitor/monitor-internal.h
+++ b/monitor/monitor-internal.h
@@ -182,5 +182,6 @@ int get_monitor_def(Monitor *mon, int64_t *pval, const char
*name);
void help_cmd(Monitor *mon, const char *name);
void handle_hmp_command(MonitorHMP *mon, const char *cmdline);
int hmp_compare_cmd(const char *name, const char *list);
+void monitor_flush_locked(Monitor *mon);
#endif
diff --git a/monitor/monitor.c b/monitor/monitor.c
index b90c0f4051..1b05ef3bdb 100644
--- a/monitor/monitor.c
+++ b/monitor/monitor.c
@@ -154,8 +154,6 @@ static inline bool monitor_is_hmp_non_interactive(const
Monitor *mon)
return !monitor_uses_readline(container_of(mon, MonitorHMP, common));
}
-static void monitor_flush_locked(Monitor *mon);
-
static gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond,
void *opaque)
{
@@ -169,7 +167,7 @@ static gboolean monitor_unblocked(GIOChannel *chan,
GIOCondition cond,
}
/* Caller must hold mon->mon_lock */
-static void monitor_flush_locked(Monitor *mon)
+void monitor_flush_locked(Monitor *mon)
{
int rc;
size_t len;
diff --git a/monitor/qmp.c b/monitor/qmp.c
index 092c527b6f..29b49ee041 100644
--- a/monitor/qmp.c
+++ b/monitor/qmp.c
@@ -46,6 +46,8 @@ struct QMPRequest {
typedef struct QMPRequest QMPRequest;
QmpCommandList qmp_commands, qmp_cap_negotiation_commands;
+static void monitor_qmp_setup_handlers_bh(void *opaque);
+static void monitor_backend_init(MonitorQMP *mon, Chardev *chr);
static bool qmp_oob_enabled(MonitorQMP *mon)
{
@@ -481,6 +483,35 @@ void monitor_data_destroy_qmp(MonitorQMP *mon)
g_queue_free(mon->qmp_requests);
}
+static bool monitor_in_list(Monitor *mon)
+{
+ Monitor *mon_tmp;
+ QTAILQ_FOREACH(mon_tmp, &mon_list, entry) {
+ if (mon_tmp == mon) {
+ return true;
+ }
+ }
+ return false;
+}
+
+static int monitor_qmp_change(void *opaque)
+{
+ MonitorQMP *mon = opaque;
+
+ monitor_data_init(&mon->common, true, false,
+ qemu_chr_has_feature(mon->common.chr.chr,
+ QEMU_CHAR_FEATURE_GCONTEXT));
+ monitor_backend_init(mon, mon->common.chr.chr);
+ qemu_mutex_lock(&mon->common.mon_lock);
+ if (mon->common.out_watch) {
+ mon->common.out_watch = 0;
+ monitor_flush_locked(&mon->common);
+ }
+ qemu_mutex_unlock(&mon->common.mon_lock);
+
+ return 0;
+}
+
static void monitor_qmp_setup_handlers_bh(void *opaque)
{
MonitorQMP *mon = opaque;
@@ -491,30 +522,15 @@ static void monitor_qmp_setup_handlers_bh(void *opaque)
assert(context);
qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
monitor_qmp_read, monitor_qmp_event,
- NULL, &mon->common, context, true);
- monitor_list_append(&mon->common);
-}
+ monitor_qmp_change, &mon->common, context, true);
-void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)
-{
- MonitorQMP *mon = g_new0(MonitorQMP, 1);
-
- if (!qemu_chr_fe_init(&mon->common.chr, chr, errp)) {
- g_free(mon);
- return;
+ if (!monitor_in_list(&mon->common)) {
+ monitor_list_append(&mon->common);
}
- qemu_chr_fe_set_echo(&mon->common.chr, true);
-
- /* Note: we run QMP monitor in I/O thread when @chr supports that */
- monitor_data_init(&mon->common, true, false,
- qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_GCONTEXT));
-
- mon->pretty = pretty;
-
- qemu_mutex_init(&mon->qmp_queue_lock);
- mon->qmp_requests = g_queue_new();
+}
- json_message_parser_init(&mon->parser, handle_qmp_command, mon, NULL);
+static void monitor_backend_init(MonitorQMP *mon, Chardev *chr)
+{
if (mon->common.use_io_thread) {
/*
* Make sure the old iowatch is gone. It's possible when
@@ -532,7 +548,29 @@ void monitor_init_qmp(Chardev *chr, bool pretty, Error
**errp)
} else {
qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
monitor_qmp_read, monitor_qmp_event,
- NULL, &mon->common, NULL, true);
- monitor_list_append(&mon->common);
+ monitor_qmp_change, &mon->common, NULL, true);
+ if (!monitor_in_list(&mon->common)) {
+ monitor_list_append(&mon->common);
+ }
}
}
+
+void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)
+{
+ MonitorQMP *mon = g_new0(MonitorQMP, 1);
+
+ if (!qemu_chr_fe_init(&mon->common.chr, chr, errp)) {
+ g_free(mon);
+ return;
+ }
+ qemu_chr_fe_set_echo(&mon->common.chr, true);
+ /* Note: we run QMP monitor in I/O thread when @chr supports that */
+ monitor_data_init(&mon->common, true, false,
+ qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_GCONTEXT));
+
+ mon->pretty = pretty;
+ qemu_mutex_init(&mon->qmp_queue_lock);
+ mon->qmp_requests = g_queue_new();
+ json_message_parser_init(&mon->parser, handle_qmp_command, mon, NULL);
+ monitor_backend_init(mon, chr);
+}
--
2.25.1
