vl: stop recording -smp in QemuOpts

-readconfig is still recording SMP options in QemuOpts instead of
using machine_opts_dict.  This means that SMP options from -readconfig
are ignored.

Just stop using QemuOpts for -smp, making it return false for
is_qemuopts_group.  Configuration files will merge the values in
machine_opts_dict using the new function machine_merge_property.

At the same time, fix -mem-prealloc which looked at QemuOpts to find the
number of guest CPUs, which it used as the default number of preallocation
threads.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

softmmu/vl.c

@@ -31,6 +31,7 @@
 #include "qapi/compat-policy.h"
 #include "qapi/error.h"
 #include "qapi/qmp/qdict.h"
+#include "qapi/qmp/qstring.h"
 #include "qapi/qmp/qjson.h"
 #include "qemu-version.h"
 #include "qemu/cutils.h"
@@ -2166,7 +2167,8 @@ static int global_init_func(void *opaque, QemuOpts *opts, Error **errp)
 static bool is_qemuopts_group(const char *group)
 {
     if (g_str_equal(group, "object") ||
-        g_str_equal(group, "machine")) {
+        g_str_equal(group, "machine") ||
+        g_str_equal(group, "smp-opts")) {
         return false;
     }
     return true;
@@ -2186,6 +2188,8 @@ static void qemu_record_config_group(const char *group, QDict *dict,
          */
         assert(!from_json);
         keyval_merge(machine_opts_dict, dict, errp);
+    } else if (g_str_equal(group, "smp-opts")) {
+        machine_merge_property("smp", dict, &error_fatal);
     } else {
         abort();
     }
@@ -2452,13 +2456,15 @@ static void qemu_validate_options(const QDict *machine_opts)
 static void qemu_process_sugar_options(void)
 {
     if (mem_prealloc) {
-        char *val;
-
-        val = g_strdup_printf("%d",
-                 (uint32_t) qemu_opt_get_number(qemu_find_opts_singleton("smp-opts"), "cpus", 1));
-        object_register_sugar_prop("memory-backend", "prealloc-threads", val,
-                                   false);
-        g_free(val);
+        QObject *smp = qdict_get(machine_opts_dict, "smp");
+        if (smp && qobject_type(smp) == QTYPE_QDICT) {
+            QObject *cpus = qdict_get(qobject_to(QDict, smp), "cpus");
+            if (cpus && qobject_type(cpus) == QTYPE_QSTRING) {
+                const char *val = qstring_get_str(qobject_to(QString, cpus));
+                object_register_sugar_prop("memory-backend", "prealloc-threads",
+                                           val, false);
+            }
+        }
         object_register_sugar_prop("memory-backend", "prealloc", "on", false);
     }