vl: Fix broken thread=xxx option of the --accel parameter

Commit bde4d920 ("Fix the -accel parameter and the documentation for
'hax'") introduced a regression by adding a new local accel_opts
variable which shadows the variable with the same name that is
declared at the beginning of the main() scope. This causes the
qemu_tcg_configure() call later to be always called with NULL, so
that the thread=xxx option gets ignored. Fix it by removing the
local accel_opts variable and use "opts" instead, which is meant
for storing temporary QemuOpts values.
And while we're at it, also change the exit(1) here to exit(0)
since asking for help is not an error.

Fixes: bde4d920Reported-by: NMarkus Armbruster <armbru@redhat.com>
Reported-by: NEmilio G. Cota <cota@braap.org>
Signed-off-by: NThomas Huth <thuth@redhat.com>
Message-Id: <1496899257-25800-1-git-send-email-thuth@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

vl.c

@@ -3757,21 +3757,18 @@ int main(int argc, char **argv, char **envp)
                 qdev_prop_register_global(&kvm_pit_lost_tick_policy);
                 break;
             }
-            case QEMU_OPTION_accel: {
-                QemuOpts *accel_opts;
-
+            case QEMU_OPTION_accel:
                 accel_opts = qemu_opts_parse_noisily(qemu_find_opts("accel"),
                                                      optarg, true);
                 optarg = qemu_opt_get(accel_opts, "accel");
                 if (!optarg || is_help_option(optarg)) {
                     error_printf("Possible accelerators: kvm, xen, hax, tcg\n");
-                    exit(1);
+                    exit(0);
                 }
-                accel_opts = qemu_opts_create(qemu_find_opts("machine"), NULL,
-                                              false, &error_abort);
-                qemu_opt_set(accel_opts, "accel", optarg, &error_abort);
+                opts = qemu_opts_create(qemu_find_opts("machine"), NULL,
+                                        false, &error_abort);
+                qemu_opt_set(opts, "accel", optarg, &error_abort);
                 break;
-            }
             case QEMU_OPTION_usb:
                 olist = qemu_find_opts("machine");
                 qemu_opts_parse_noisily(olist, "usb=on", false);