Currently, the conflict between -incoming and -loadvm is only detected
when loading the snapshot fails because the image is still inactive for
the incoming migration. This results in a suboptimal error message:

$ ./qemu-system-x86_64 -hda /tmp/test.qcow2 -loadvm foo -incoming defer
qemu-system-x86_64: Device 'ide0-hd0' is writable but does not support snapshots

Catch the situation already in qemu_validate_options() to improve the
message:

$ ./qemu-system-x86_64 -hda /tmp/test.qcow2 -loadvm foo -incoming defer
qemu-system-x86_64: 'incoming' and 'loadvm' options are mutually exclusive

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 system/vl.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/system/vl.c b/system/vl.c
index 2bcd9efb9a..6b87bfa32c 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -2426,6 +2426,10 @@ static void qemu_validate_options(const QDict *machine_opts)
           }
     }
 
+    if (loadvm && incoming) {
+        error_report("'incoming' and 'loadvm' options are mutually exclusive");
+        exit(EXIT_FAILURE);
+    }
     if (loadvm && preconfig_requested) {
         error_report("'preconfig' and 'loadvm' options are "
                      "mutually exclusive");
-- 
2.43.0