[Qemu-devel] [RFC PATCH] vl: only display available accelerators

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

examples configuring with '--enable-kvm --disable-tcg'

- before

  $ qemu-system-x86_64 -accel help
  Possible accelerators: kvm, xen, hax, tcg

  $ qemu-system-x86_64 -accel tcg
  qemu-system-x86_64: -machine accel=tcg: No accelerator found

  # qemu-system-x86_64 -accel hax
  qemu-system-x86_64: -machine accel=hax: No accelerator found

  # qemu-system-x86_64 -accel xen
  xencall: error: Could not obtain handle on privileged command interface: No such file or directory
  xen be core: xen be core: can't open xen interface
  can't open xen interface
  qemu-system-x86_64: failed to initialize Xen: Operation not permitted

- after

  $ qemu-system-x86_64 -accel help
  Possible accelerators: kvm

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
RFC because:
    - I don't think this is the nicest way, too much #ifdef'fery in main()
    - I'm not sure the correct use of CONFIG_KVM_IS_POSSIBLE
    - shouldn't CONFIG_XEN/CONFIG_HAX be as poisoned as CONFIG_KVM?

 vl.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/vl.c b/vl.c
index ec299099ff..13fce86a6e 100644
--- a/vl.c
+++ b/vl.c
@@ -3883,7 +3883,20 @@ int main(int argc, char **argv, char **envp)
                                                      optarg, true);
                 optarg = qemu_opt_get(accel_opts, "accel");
                 if (!optarg || is_help_option(optarg)) {
-                    error_printf("Possible accelerators: kvm, xen, hax, tcg\n");
+                    error_printf("Possible accelerators: ");
+#ifdef CONFIG_KVM_IS_POSSIBLE
+                    error_printf("kvm ");
+#endif
+#ifdef CONFIG_XEN
+                    error_printf("xen ");
+#endif
+#ifdef CONFIG_HAX
+                    error_printf("hax ");
+#endif
+#ifdef CONFIG_TCG
+                    error_printf("tcg ");
+#endif
+                    error_printf("\n");
                     exit(0);
                 }
                 opts = qemu_opts_create(qemu_find_opts("machine"), NULL,
-- 
2.15.0.rc2