[PATCH v2] qemu-config: add error propagation to qemu_config_parse

[Paolo Bonzini <pbonzini@redhat.com>]

This enables some simplification of vl.c via error_fatal, and improves
error messages.  Before:

Before:
  $ ./qemu-system-x86_64 -readconfig .
  qemu-system-x86_64: error reading file
  qemu-system-x86_64: -readconfig .: read config .: Invalid argument
  $ /usr/libexec/qemu-kvm -readconfig foo
  qemu-kvm: -readconfig foo: read config foo: No such file or directory

After:

  $ ./qemu-system-x86_64 -readconfig .
  qemu-system-x86_64: -readconfig .: error reading file: Is a directory
  $ ./qemu-system-x86_64 -readconfig foo
  qemu-system-x86_64: -readconfig foo: Cannot read config file foo: No such file or directory

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/blkdebug.c           |  3 +--
 include/qemu/config-file.h |  5 +++--
 softmmu/vl.c               | 29 +++++++++++------------------
 util/qemu-config.c         | 23 ++++++++++++-----------
 4 files changed, 27 insertions(+), 33 deletions(-)

diff --git a/block/blkdebug.c b/block/blkdebug.c
index 5fe6172da9..7eaa8a28bf 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -279,9 +279,8 @@ static int read_config(BDRVBlkdebugState *s, const char *filename,
             return -errno;
         }
 
-        ret = qemu_config_parse(f, config_groups, filename);
+        ret = qemu_config_parse(f, config_groups, filename, errp);
         if (ret < 0) {
-            error_setg(errp, "Could not parse blkdebug config file");
             goto fail;
         }
     }
diff --git a/include/qemu/config-file.h b/include/qemu/config-file.h
index 29226107bd..8d3e53ae4d 100644
--- a/include/qemu/config-file.h
+++ b/include/qemu/config-file.h
@@ -11,9 +11,10 @@ void qemu_add_drive_opts(QemuOptsList *list);
 int qemu_global_option(const char *str);
 
 void qemu_config_write(FILE *fp);
-int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname);
+int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname,
+                      Error **errp);
 
-int qemu_read_config_file(const char *filename);
+int qemu_read_config_file(const char *filename, Error **errp);
 
 /* Parse QDict options as a replacement for a config file (allowing multiple
    enumerated (0..(n-1)) configuration "sections") */
diff --git a/softmmu/vl.c b/softmmu/vl.c
index e67f91dd37..e80859c40d 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2062,17 +2062,19 @@ static int global_init_func(void *opaque, QemuOpts *opts, Error **errp)
     return 0;
 }
 
-static int qemu_read_default_config_file(void)
+static void qemu_read_default_config_file(Error **errp)
 {
+    ERRP_GUARD();
     int ret;
     g_autofree char *file = get_relocated_path(CONFIG_QEMU_CONFDIR "/qemu.conf");
 
-    ret = qemu_read_config_file(file);
-    if (ret < 0 && ret != -ENOENT) {
-        return ret;
+    ret = qemu_read_config_file(file, errp);
+    if (ret < 0) {
+        if (ret == -ENOENT) {
+            error_free(*errp);
+            *errp = NULL;
+        }
     }
-
-    return 0;
 }
 
 static int qemu_set_option(const char *str)
@@ -2640,9 +2642,7 @@ void qemu_init(int argc, char **argv, char **envp)
     }
 
     if (userconfig) {
-        if (qemu_read_default_config_file() < 0) {
-            exit(1);
-        }
+        qemu_read_default_config_file(&error_fatal);
     }
 
     /* second pass of option parsing */
@@ -3330,15 +3330,8 @@ void qemu_init(int argc, char **argv, char **envp)
                 qemu_plugin_opt_parse(optarg, &plugin_list);
                 break;
             case QEMU_OPTION_readconfig:
-                {
-                    int ret = qemu_read_config_file(optarg);
-                    if (ret < 0) {
-                        error_report("read config %s: %s", optarg,
-                                     strerror(-ret));
-                        exit(1);
-                    }
-                    break;
-                }
+                qemu_read_config_file(optarg, &error_fatal);
+                break;
             case QEMU_OPTION_spice:
                 olist = qemu_find_opts_err("spice", NULL);
                 if (!olist) {
diff --git a/util/qemu-config.c b/util/qemu-config.c
index e2a700b284..af89df109d 100644
--- a/util/qemu-config.c
+++ b/util/qemu-config.c
@@ -350,7 +350,7 @@ 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)
+int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname, Error **errp)
 {
     char line[1024], group[64], id[64], arg[64], value[1024];
     Location loc;
@@ -375,7 +375,7 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname)
             /* group with id */
             list = find_list(lists, group, &local_err);
             if (local_err) {
-                error_report_err(local_err);
+                error_propagate(errp, local_err);
                 goto out;
             }
             opts = qemu_opts_create(list, id, 1, NULL);
@@ -386,7 +386,7 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname)
             /* group without id */
             list = find_list(lists, group, &local_err);
             if (local_err) {
-                error_report_err(local_err);
+                error_propagate(errp, local_err);
                 goto out;
             }
             opts = qemu_opts_create(list, NULL, 0, &error_abort);
@@ -398,21 +398,21 @@ int qemu_config_parse(FILE *fp, QemuOptsList **lists, const char *fname)
             sscanf(line, " %63s = \"\"", arg) == 1) {
             /* arg = value */
             if (opts == NULL) {
-                error_report("no group defined");
+                error_setg(errp, "no group defined");
                 goto out;
             }
-            if (!qemu_opt_set(opts, arg, value, &local_err)) {
-                error_report_err(local_err);
+            if (!qemu_opt_set(opts, arg, value, errp)) {
                 goto out;
             }
             continue;
         }
-        error_report("parse error");
+        error_setg(errp, "parse error");
         goto out;
     }
     if (ferror(fp)) {
-        error_report("error reading file");
-        goto out;
+        loc_pop(&loc);
+        error_setg_errno(errp, errno, "error reading file");
+        return res;
     }
     res = count;
 out:
@@ -420,16 +420,17 @@ out:
     return res;
 }
 
-int qemu_read_config_file(const char *filename)
+int qemu_read_config_file(const char *filename, Error **errp)
 {
     FILE *f = fopen(filename, "r");
     int ret;
 
     if (f == NULL) {
+        error_setg_errno(errp, errno, "Cannot read config file %s", filename);
         return -errno;
     }
 
-    ret = qemu_config_parse(f, vm_config_groups, filename);
+    ret = qemu_config_parse(f, vm_config_groups, filename, errp);
     fclose(f);
     return ret;
 }
-- 
2.26.2