qemu-config: parse configuration files to a QDict

Change the parser to put the values into a QDict and pass them
to a callback.  qemu_config_parse's QemuOpts creation is
itself turned into a callback function.

This is useful for -readconfig to support keyval-based options;
getting a QDict from the parser removes a roundtrip from
QDict to QemuOpts and then back to QDict.

Unfortunately there is a disadvantage in that semantic errors will
point to the last line of the group, because the entries of the QDict
do not have a location attached.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210524105752.3318299-2-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/qemu/config-file.h

@@ -1,6 +1,8 @@
 #ifndef QEMU_CONFIG_FILE_H
 #define QEMU_CONFIG_FILE_H
 
+typedef void QEMUConfigCB(const char *group, QDict *qdict, void *opaque, Error **errp);
+
 void qemu_load_module_for_opts(const char *group);
 QemuOptsList *qemu_find_opts(const char *group);
 QemuOptsList *qemu_find_opts_err(const char *group, Error **errp);
@@ -14,7 +16,10 @@ void qemu_config_write(FILE *fp);
 int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname,
                       Error **errp);
 
-int qemu_read_config_file(const char *filename, Error **errp);
+/* A default callback for qemu_read_config_file().  */
+void qemu_config_do_parse(const char *group, QDict *qdict, void *opaque, Error **errp);
+
+int qemu_read_config_file(const char *filename, QEMUConfigCB *f, Error **errp);
 
 /* Parse QDict options as a replacement for a config file (allowing multiple
    enumerated (0..(n-1)) configuration "sections") */

softmmu/vl.c

@@ -2133,7 +2133,7 @@ static void qemu_read_default_config_file(Error **errp)
     int ret;
     g_autofree char *file = get_relocated_path(CONFIG_QEMU_CONFDIR "/qemu.conf");
 
-    ret = qemu_read_config_file(file, errp);
+    ret = qemu_read_config_file(file, qemu_config_do_parse, errp);
     if (ret < 0) {
         if (ret == -ENOENT) {
             error_free(*errp);
@@ -3399,7 +3399,7 @@ void qemu_init(int argc, char **argv, char **envp)
                 qemu_plugin_opt_parse(optarg, &plugin_list);
                 break;
             case QEMU_OPTION_readconfig:
-                qemu_read_config_file(optarg, &error_fatal);
+                qemu_read_config_file(optarg, qemu_config_do_parse, &error_fatal);
                 break;
             case QEMU_OPTION_spice:
                 olist = qemu_find_opts_err("spice", NULL);

util/qemu-config.c

@@ -2,6 +2,7 @@
 #include "block/qdict.h" /* for qdict_extract_subqdict() */
 #include "qapi/error.h"
 #include "qapi/qapi-commands-misc.h"
+#include "qapi/qmp/qerror.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/qmp/qlist.h"
 #include "qemu/error-report.h"
@@ -351,19 +352,19 @@ void qemu_config_write(FILE *fp)
 }
 
 /* Returns number of config groups on success, -errno on error */
-int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname, Error **errp)
+static int qemu_config_foreach(FILE *fp, QEMUConfigCB *cb, void *opaque,
+                               const char *fname, Error **errp)
 {
-    char line[1024], group[64], id[64], arg[64], value[1024];
+    char line[1024], prev_group[64], group[64], arg[64], value[1024];
     Location loc;
-    QemuOptsList *list = NULL;
     Error *local_err = NULL;
-    QemuOpts *opts = NULL;
+    QDict *qdict = NULL;
     int res = -EINVAL, lno = 0;
     int count = 0;
 
     loc_push_none(&loc);
     while (fgets(line, sizeof(line), fp) != NULL) {
-        loc_set_file(fname, ++lno);
+        ++lno;
         if (line[0] == '\n') {
             /* skip empty lines */
             continue;
@@ -372,39 +373,39 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname, Error *
             /* comment */
             continue;
         }
-        if (sscanf(line, "[%63s \"%63[^\"]\"]", group, id) == 2) {
+        if (line[0] == '[') {
-            /* group with id */
+            QDict *prev = qdict;
-            list = find_list(lists, group, &local_err);
+            if (sscanf(line, "[%63s \"%63[^\"]\"]", group, value) == 2) {
+                qdict = qdict_new();
+                qdict_put_str(qdict, "id", value);
+                count++;
+            } else if (sscanf(line, "[%63[^]]]", group) == 1) {
+                qdict = qdict_new();
+                count++;
+            }
+            if (qdict != prev) {
+                if (prev) {
+                    cb(prev_group, prev, opaque, &local_err);
+                    qobject_unref(prev);
                     if (local_err) {
                         error_propagate(errp, local_err);
                         goto out;
                     }
-            opts = qemu_opts_create(list, id, 1, NULL);
+                }
-            count++;
+                strcpy(prev_group, group);
                 continue;
             }
-        if (sscanf(line, "[%63[^]]]", group) == 1) {
-            /* group without id */
-            list = find_list(lists, group, &local_err);
-            if (local_err) {
-                error_propagate(errp, local_err);
-                goto out;
-            }
-            opts = qemu_opts_create(list, NULL, 0, &error_abort);
-            count++;
-            continue;
         }
+        loc_set_file(fname, lno);
         value[0] = '\0';
         if (sscanf(line, " %63s = \"%1023[^\"]\"", arg, value) == 2 ||
             sscanf(line, " %63s = \"\"", arg) == 1) {
             /* arg = value */
-            if (opts == NULL) {
+            if (qdict == NULL) {
                 error_setg(errp, "no group defined");
                 goto out;
             }
-            if (!qemu_opt_set(opts, arg, value, errp)) {
+            qdict_put_str(qdict, arg, value);
-                goto out;
-            }
             continue;
         }
         error_setg(errp, "parse error");
@@ -417,11 +418,48 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname, Error *
     }
     res = count;
 out:
+    if (qdict) {
+        cb(group, qdict, opaque, errp);
+        qobject_unref(qdict);
+    }
     loc_pop(&loc);
     return res;
 }
 
-int qemu_read_config_file(const char *filename, Error **errp)
+void qemu_config_do_parse(const char *group, QDict *qdict, void *opaque, Error **errp)
+{
+    QemuOptsList **lists = opaque;
+    const char *id = qdict_get_try_str(qdict, "id");
+    QemuOptsList *list;
+    QemuOpts *opts;
+    const QDictEntry *unrecognized;
+
+    list = find_list(lists, group, errp);
+    if (!list) {
+        return;
+    }
+
+    opts = qemu_opts_create(list, id, 1, errp);
+    if (!opts) {
+        return;
+    }
+    if (!qemu_opts_absorb_qdict(opts, qdict, errp)) {
+        qemu_opts_del(opts);
+        return;
+    }
+    unrecognized = qdict_first(qdict);
+    if (unrecognized) {
+        error_setg(errp, QERR_INVALID_PARAMETER, unrecognized->key);
+        qemu_opts_del(opts);
+    }
+}
+
+int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname, Error **errp)
+{
+    return qemu_config_foreach(fp, qemu_config_do_parse, lists, fname, errp);
+}
+
+int qemu_read_config_file(const char *filename, QEMUConfigCB *cb, Error **errp)
 {
     FILE *f = fopen(filename, "r");
     int ret;
@@ -431,7 +469,7 @@ int qemu_read_config_file(const char *filename, Error **errp)
         return -errno;
     }
 
-    ret = qemu_config_parse(f, vm_config_groups, filename, errp);
+    ret = qemu_config_foreach(f, cb, vm_config_groups, filename, errp);
     fclose(f);
     return ret;
 }