qemu-config: qemu_read_config_file() reads the normal config file

Introduce a new function qemu_read_config_file which reads the VM configuration
from a config file. Unlike qemu_config_parse it doesn't take a open file but a
filename and reduces code duplication as a side effect.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

qemu-config.c

@@ -488,3 +488,18 @@ out:
     loc_pop(&loc);
     return res;
 }
+
+int qemu_read_config_file(const char *filename)
+{
+    FILE *f = fopen(filename, "r");
+    if (f == NULL) {
+        return -errno;
+    }
+
+    if (qemu_config_parse(f, filename) != 0) {
+        return -EINVAL;
+    }
+    fclose(f);
+
+    return 0;
+}

qemu-config.h

@@ -19,4 +19,6 @@ void qemu_add_globals(void);
 void qemu_config_write(FILE *fp);
 int qemu_config_parse(FILE *fp, const char *fname);
 
+int qemu_read_config_file(const char *filename);
+
 #endif /* QEMU_CONFIG_H */

vl.c

@@ -2653,25 +2653,16 @@ int main(int argc, char **argv, char **envp)
     }
 
     if (defconfig) {
-        const char *fname;
-        FILE *fp;
+        int ret;
 
-        fname = CONFIG_QEMU_CONFDIR "/qemu.conf";
-        fp = fopen(fname, "r");
-        if (fp) {
-            if (qemu_config_parse(fp, fname) != 0) {
-                exit(1);
-            }
-            fclose(fp);
+        ret = qemu_read_config_file(CONFIG_QEMU_CONFDIR "/qemu.conf");
+        if (ret == -EINVAL) {
+            exit(1);
         }
 
-        fname = arch_config_name;
-        fp = fopen(fname, "r");
-        if (fp) {
-            if (qemu_config_parse(fp, fname) != 0) {
-                exit(1);
-            }
-            fclose(fp);
+        ret = qemu_read_config_file(arch_config_name);
+        if (ret == -EINVAL) {
+            exit(1);
         }
     }
     cpudef_init();
@@ -3327,16 +3318,12 @@ int main(int argc, char **argv, char **envp)
                 break;
             case QEMU_OPTION_readconfig:
                 {
-                    FILE *fp;
-                    fp = fopen(optarg, "r");
-                    if (fp == NULL) {
-                        fprintf(stderr, "open %s: %s\n", optarg, strerror(errno));
+                    int ret = qemu_read_config_file(optarg);
+                    if (ret < 0) {
+                        fprintf(stderr, "read config %s: %s\n", optarg,
+                            strerror(-ret));
                         exit(1);
                     }
-                    if (qemu_config_parse(fp, optarg) != 0) {
-                        exit(1);
-                    }
-                    fclose(fp);
                     break;
                 }
             case QEMU_OPTION_writeconfig: