cpu: Add generic cpu_list()

Add generic cpu_list() to replace the individual target's implementation
in the subsequent commits. Currently, there are 3 targets with no cpu_list()
implementation: microblaze and nios2. With this applied, those two targets
switch to the generic cpu_list().

[gshan@gshan q]$ ./build/qemu-system-microblaze -cpu ?
Available CPUs:
  microblaze-cpu

[gshan@gshan q]$ ./build/qemu-system-nios2 -cpu ?
Available CPUs:
  nios2-cpu

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231114235628.534334-7-gshan@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

bsd-user/main.c

@@ -378,10 +378,7 @@ int main(int argc, char **argv)
         } else if (!strcmp(r, "cpu")) {
             cpu_model = argv[optind++];
             if (is_help_option(cpu_model)) {
-                /* XXX: implement xxx_cpu_list for targets that still miss it */
-#if defined(cpu_list)
-                cpu_list();
-#endif
+                list_cpus();
                 exit(1);
             }
         } else if (!strcmp(r, "B")) {

cpu-target.c

@@ -24,6 +24,7 @@
 #include "hw/qdev-core.h"
 #include "hw/qdev-properties.h"
 #include "qemu/error-report.h"
+#include "qemu/qemu-print.h"
 #include "migration/vmstate.h"
 #ifdef CONFIG_USER_ONLY
 #include "qemu.h"
@@ -283,12 +284,34 @@ const char *parse_cpu_option(const char *cpu_option)
     return cpu_type;
 }
 
+#ifndef cpu_list
+static void cpu_list_entry(gpointer data, gpointer user_data)
+{
+    CPUClass *cc = CPU_CLASS(OBJECT_CLASS(data));
+    const char *typename = object_class_get_name(OBJECT_CLASS(data));
+    g_autofree char *model = cpu_model_from_type(typename);
+
+    if (cc->deprecation_note) {
+        qemu_printf("  %s (deprecated)\n", model);
+    } else {
+        qemu_printf("  %s\n", model);
+    }
+}
+
+static void cpu_list(void)
+{
+    GSList *list;
+
+    list = object_class_get_list_sorted(TYPE_CPU, false);
+    qemu_printf("Available CPUs:\n");
+    g_slist_foreach(list, cpu_list_entry, NULL);
+    g_slist_free(list);
+}
+#endif
+
 void list_cpus(void)
 {
-    /* XXX: implement xxx_cpu_list for targets that still miss it */
-#if defined(cpu_list)
     cpu_list();
-#endif
 }
 
 #if defined(CONFIG_USER_ONLY)