system: guard HMP initialization paths with CONFIG_HMP

- disable default monitor when HMP is not available
- hide 'readline' from -mon help text
- error out on mux chardev monitor when no HMP
- skip HMP monitor terminal for gdb, return E01 for 'qRcmd' remote
  commands

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-ID: <20260828-qemu-no-hmp-v5-28-9227de146347@redhat.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/chardev/char.c b/chardev/char.c
index 22e5bae388..c6c8133f5c 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -804,8 +804,9 @@ static Chardev *qemu_chr_new_from_name(const char *label, const char *filename,
     }
 
     if (qemu_opt_get_bool(opts, "mux", 0)) {
-        const char *chardev_id = qemu_opts_id(opts);
         assert(permit_mux_mon);
+#ifdef CONFIG_HMP
+        const char *chardev_id = qemu_opts_id(opts);
         monitor_new_hmp(NULL, chardev_id, true, &err);
         if (err) {
             error_report_err(err);
@@ -813,6 +814,12 @@ static Chardev *qemu_chr_new_from_name(const char *label, const char *filename,
             chr = NULL;
             goto out;
         }
+#else
+        error_report("HMP monitor is disabled");
+        object_unparent(OBJECT(chr));
+        chr = NULL;
+        goto out;
+#endif
     }
 
 out: