[PATCH v3 3/3] cpu, softmmu/vl.c: Change parsing of -cpu argument to allow -cpu cpu, help to print options for the CPU type similar to how the '-device' option works.

[Dinah Baum <dinahbaum123@gmail.com>]

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1480
Signed-off-by: Dinah Baum <dinahbaum123@gmail.com>

Signed-off-by: Dinah Baum <dinahbaum123@gmail.com>
---
 cpu.c                    | 41 ++++++++++++++++++++++++++++++++++++++++
 include/qapi/qmp/qdict.h |  1 +
 qemu-options.hx          |  7 ++++---
 qobject/qdict.c          |  5 +++++
 softmmu/vl.c             | 35 +++++++++++++++++++++++++++++++++-
 5 files changed, 85 insertions(+), 4 deletions(-)

diff --git a/cpu.c b/cpu.c
index a99d09cd47..9971ffeeba 100644
--- a/cpu.c
+++ b/cpu.c
@@ -43,6 +43,10 @@
 #include "trace/trace-root.h"
 #include "qemu/accel.h"
 #include "qemu/plugin.h"
+#include "qemu/cutils.h"
+#include "qemu/qemu-print.h"
+#include "qapi/qmp/qdict.h"
+#include "qapi/qmp/qobject.h"
 
 uintptr_t qemu_host_page_size;
 intptr_t qemu_host_page_mask;
@@ -312,6 +316,43 @@ CpuModelExpansionInfo *qmp_query_cpu_model_expansion(CpuModelExpansionType type,
     return get_cpu_model_expansion_info(type, model, errp);
 }
 
+void list_cpu_model_expansion(CpuModelExpansionType type,
+                              CpuModelInfo *model,
+                              Error **errp)
+{
+    CpuModelExpansionInfo *expansion_info;
+    QDict *qdict;
+    QDictEntry *qdict_entry;
+    const char *key;
+    QObject *obj;
+    QType q_type;
+    GPtrArray *array;
+    int i;
+    const char *type_name;
+
+    expansion_info = get_cpu_model_expansion_info(type, model, errp);
+    if (expansion_info) {
+        qdict = qobject_to(QDict, expansion_info->model->props);
+        if (qdict) {
+            qemu_printf("%s features:\n", model->name);
+            array = g_ptr_array_new();
+            for (qdict_entry = (QDictEntry *)qdict_first(qdict); qdict_entry;
+                 qdict_entry = (QDictEntry *)qdict_next(qdict, qdict_entry)) {
+                g_ptr_array_add(array, qdict_entry);
+            }
+            g_ptr_array_sort(array, (GCompareFunc)dict_key_compare);
+            for (i = 0; i < array->len; i++) {
+                qdict_entry = array->pdata[i];
+                key = qdict_entry_key(qdict_entry);
+                obj = qdict_get(qdict, key);
+                q_type = qobject_type(obj);
+                type_name = QType_str(q_type);
+                qemu_printf("  %s=<%s>\n", key, type_name);
+            }
+        }
+    }
+}
+
 #if defined(CONFIG_USER_ONLY)
 void tb_invalidate_phys_addr(hwaddr addr)
 {
diff --git a/include/qapi/qmp/qdict.h b/include/qapi/qmp/qdict.h
index 82e90fc072..d0b6c3d358 100644
--- a/include/qapi/qmp/qdict.h
+++ b/include/qapi/qmp/qdict.h
@@ -67,5 +67,6 @@ bool qdict_get_try_bool(const QDict *qdict, const char *key, bool def_value);
 const char *qdict_get_try_str(const QDict *qdict, const char *key);
 
 QDict *qdict_clone_shallow(const QDict *src);
+int dict_key_compare(QDictEntry **entry1, QDictEntry **entry2);
 
 #endif /* QDICT_H */
diff --git a/qemu-options.hx b/qemu-options.hx
index 29b98c3d4c..e0f0284927 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -169,11 +169,12 @@ SRST
 ERST
 
 DEF("cpu", HAS_ARG, QEMU_OPTION_cpu,
-    "-cpu cpu        select CPU ('-cpu help' for list)\n", QEMU_ARCH_ALL)
+    "-cpu cpu        select CPU ('-cpu help' for list)\n"
+    "                use '-cpu cpu,help' to print possible properties\n", QEMU_ARCH_ALL)
 SRST
 ``-cpu model``
-    Select CPU model (``-cpu help`` for list and additional feature
-    selection)
+    Select CPU model (``-cpu help`` and ``-cpu cpu,help``) for list and additional feature
+    selection
 ERST
 
 DEF("accel", HAS_ARG, QEMU_OPTION_accel,
diff --git a/qobject/qdict.c b/qobject/qdict.c
index 8faff230d3..31407e62f6 100644
--- a/qobject/qdict.c
+++ b/qobject/qdict.c
@@ -447,3 +447,8 @@ void qdict_unref(QDict *q)
 {
     qobject_unref(q);
 }
+
+int dict_key_compare(QDictEntry **entry1, QDictEntry **entry2)
+{
+    return g_strcmp0(qdict_entry_key(*entry1), qdict_entry_key(*entry2));
+}
diff --git a/softmmu/vl.c b/softmmu/vl.c
index b0b96f67fa..1fd87f2c06 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -501,6 +501,15 @@ static QemuOptsList qemu_action_opts = {
     },
 };
 
+static QemuOptsList qemu_cpu_opts = {
+    .name = "cpu",
+    .implied_opt_name = "cpu",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_cpu_opts.head),
+    .desc = {
+        { /* end of list */ }
+    },
+};
+
 const char *qemu_get_vm_name(void)
 {
     return qemu_name;
@@ -1159,6 +1168,26 @@ static int device_init_func(void *opaque, QemuOpts *opts, Error **errp)
     return 0;
 }
 
+static int cpu_help_func(void *opaque, QemuOpts *opts, Error **errp)
+{
+    CpuModelInfo *model;
+
+    if (cpu_option && is_help_option(cpu_option)) {
+        list_cpus();
+        return 1;
+    }
+
+    if (!cpu_option || !qemu_opt_has_help_opt(opts)) {
+        return 0;
+    }
+
+    model = g_new0(CpuModelInfo, 1);
+    model->name = (char *)qemu_opt_get(opts, "cpu");
+    /* TODO: handle other expansion cases */
+    list_cpu_model_expansion(CPU_MODEL_EXPANSION_TYPE_FULL, model, errp);
+    return 1;
+}
+
 static int chardev_init_func(void *opaque, QemuOpts *opts, Error **errp)
 {
     Error *local_err = NULL;
@@ -2466,7 +2495,9 @@ static void qemu_process_help_options(void)
         list_cpus();
         exit(0);
     }
-
+    if (qemu_opts_foreach(qemu_find_opts("cpu"), cpu_help_func, NULL, NULL)) {
+        exit(0);
+    }
     if (qemu_opts_foreach(qemu_find_opts("device"),
                           device_help_func, NULL, NULL)) {
         exit(0);
@@ -2704,6 +2735,7 @@ void qemu_init(int argc, char **argv)
     qemu_add_opts(&qemu_semihosting_config_opts);
     qemu_add_opts(&qemu_fw_cfg_opts);
     qemu_add_opts(&qemu_action_opts);
+    qemu_add_opts(&qemu_cpu_opts);
     module_call_init(MODULE_INIT_OPTS);
 
     error_init(argv[0]);
@@ -2755,6 +2787,7 @@ void qemu_init(int argc, char **argv)
             switch(popt->index) {
             case QEMU_OPTION_cpu:
                 /* hw initialization will check this */
+                qemu_opts_parse_noisily(qemu_find_opts("cpu"), optarg, true);
                 cpu_option = optarg;
                 break;
             case QEMU_OPTION_hda:
-- 
2.30.2