softmmu/vl: Let -fw_cfg option take a 'gen_id' argument

The 'gen_id' argument refers to a QOM object able to produce
data consumable by the fw_cfg device. The producer object must
implement the FW_CFG_DATA_GENERATOR interface.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200623172726.21040-4-philmd@redhat.com>

softmmu/vl.c

@@ -489,6 +489,11 @@ static QemuOptsList qemu_fw_cfg_opts = {
             .name = "string",
             .type = QEMU_OPT_STRING,
             .help = "Sets content of the blob to be inserted from a string",
+        }, {
+            .name = "gen_id",
+            .type = QEMU_OPT_STRING,
+            .help = "Sets id of the object generating the fw_cfg blob "
+                    "to be inserted",
         },
         { /* end of list */ }
     },
@@ -2020,7 +2025,7 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp)
 {
     gchar *buf;
     size_t size;
-    const char *name, *file, *str;
+    const char *name, *file, *str, *gen_id;
     FWCfgState *fw_cfg = (FWCfgState *) opaque;
 
     if (fw_cfg == NULL) {
@@ -2030,14 +2035,13 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp)
     name = qemu_opt_get(opts, "name");
     file = qemu_opt_get(opts, "file");
     str = qemu_opt_get(opts, "string");
+    gen_id = qemu_opt_get(opts, "gen_id");
 
-    /* we need name and either a file or the content string */
-    if (!(nonempty_str(name) && (nonempty_str(file) || nonempty_str(str)))) {
-        error_setg(errp, "invalid argument(s)");
-        return -1;
-    }
-    if (nonempty_str(file) && nonempty_str(str)) {
-        error_setg(errp, "file and string are mutually exclusive");
+    /* we need the name, and exactly one of: file, content string, gen_id */
+    if (!nonempty_str(name) ||
+        nonempty_str(file) + nonempty_str(str) + nonempty_str(gen_id) != 1) {
+        error_setg(errp, "name, plus exactly one of file,"
+                         " string and gen_id, are needed");
         return -1;
     }
     if (strlen(name) > FW_CFG_MAX_FILE_PATH - 1) {
@@ -2052,6 +2056,15 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp)
     if (nonempty_str(str)) {
         size = strlen(str); /* NUL terminator NOT included in fw_cfg blob */
         buf = g_memdup(str, size);
+    } else if (nonempty_str(gen_id)) {
+        Error *local_err = NULL;
+
+        fw_cfg_add_from_generator(fw_cfg, name, gen_id, errp);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            return -1;
+        }
+        return 0;
     } else {
         GError *err = NULL;
         if (!g_file_get_contents(file, &buf, &size, &err)) {