vhost-user: Improve -netdev/netdev_add/-net/... error reporting

When -netdev vhost-user fails, it first reports a specific error, then
one or more generic ones, like this:

    $ qemu-system-x86_64 -netdev vhost-user,id=foo,chardev=xxx
    qemu-system-x86_64: -netdev vhost-user,id=foo,chardev=xxx: chardev "xxx" not found
    qemu-system-x86_64: -netdev vhost-user,id=foo,chardev=xxx: No suitable chardev found
    qemu-system-x86_64: -netdev vhost-user,id=foo,chardev=xxx: Device 'vhost-user' could not be initialized

With the command line, the messages go to stderr.  In HMP, they go to
the monitor.  In QMP, the last one becomes the error reply, and the
others go to stderr.

Convert net_init_vhost_user() and its helpers to Error.  This
suppresses the unwanted unspecific error messages, and makes the
specific error the QMP error reply.

Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 12 insertions, 13 deletions

diff --git a/net/vhost-user.c b/net/vhost-user.c
index 7e8a9ec4e8..3930741fb6 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -170,33 +170,34 @@ static int net_vhost_chardev_opts(void *opaque,
     } else if (strcmp(name, "server") == 0) {
         props->is_server = true;
     } else {
-        error_report("vhost-user does not support a chardev"
-                     " with the following option:\n %s = %s",
-                     name, value);
+        error_setg(errp,
+                   "vhost-user does not support a chardev with option %s=%s",
+                   name, value);
         return -1;
     }
     return 0;
 }
 
-static CharDriverState *net_vhost_parse_chardev(const NetdevVhostUserOptions *opts)
+static CharDriverState *net_vhost_parse_chardev(
+    const NetdevVhostUserOptions *opts, Error **errp)
 {
     CharDriverState *chr = qemu_chr_find(opts->chardev);
     VhostUserChardevProps props;
 
     if (chr == NULL) {
-        error_report("chardev \"%s\" not found", opts->chardev);
+        error_setg(errp, "chardev \"%s\" not found", opts->chardev);
         return NULL;
     }
 
     /* inspect chardev opts */
     memset(&props, 0, sizeof(props));
-    if (qemu_opt_foreach(chr->opts, net_vhost_chardev_opts, &props, NULL)) {
+    if (qemu_opt_foreach(chr->opts, net_vhost_chardev_opts, &props, errp)) {
         return NULL;
     }
 
     if (!props.is_socket || !props.is_unix) {
-        error_report("chardev \"%s\" is not a unix socket",
-                     opts->chardev);
+        error_setg(errp, "chardev \"%s\" is not a unix socket",
+                   opts->chardev);
         return NULL;
     }
 
@@ -220,7 +221,7 @@ static int net_vhost_check_net(void *opaque, QemuOpts *opts, Error **errp)
 
     if (strcmp(netdev, name) == 0 &&
         strncmp(driver, virtio_name, strlen(virtio_name)) != 0) {
-        error_report("vhost-user requires frontend driver virtio-net-*");
+        error_setg(errp, "vhost-user requires frontend driver virtio-net-*");
         return -1;
     }
 
@@ -230,7 +231,6 @@ static int net_vhost_check_net(void *opaque, QemuOpts *opts, Error **errp)
 int net_init_vhost_user(const NetClientOptions *opts, const char *name,
                         NetClientState *peer, Error **errp)
 {
-    /* FIXME error_setg(errp, ...) on failure */
     uint32_t queues;
     const NetdevVhostUserOptions *vhost_user_opts;
     CharDriverState *chr;
@@ -238,15 +238,14 @@ int net_init_vhost_user(const NetClientOptions *opts, const char *name,
     assert(opts->kind == NET_CLIENT_OPTIONS_KIND_VHOST_USER);
     vhost_user_opts = opts->vhost_user;
 
-    chr = net_vhost_parse_chardev(vhost_user_opts);
+    chr = net_vhost_parse_chardev(vhost_user_opts, errp);
     if (!chr) {
-        error_report("No suitable chardev found");
         return -1;
     }
 
     /* verify net frontend */
     if (qemu_opts_foreach(qemu_find_opts("device"), net_vhost_check_net,
-                          (char *)name, NULL)) {
+                          (char *)name, errp)) {
         return -1;
     }