migration: Accept 'cont' only after successful incoming migration

When a 'cont' is issued on a VM that's just waiting for an incoming
migration, the VM reboots and boots into the guest, possibly corrupting
its storage since it could be shared with another VM running elsewhere.

Ensure that a VM started with '-incoming' is only run when an incoming
migration successfully completes.

A new qerror, QERR_MIGRATION_EXPECTED, is added to signal that 'cont'
failed due to no incoming migration has been attempted yet.

Reported-by: Laine Stump <laine@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/qerror.c b/qerror.c
index 2f6f59061f..0af3ab32bd 100644
--- a/qerror.c
+++ b/qerror.c
@@ -141,6 +141,10 @@ static const QErrorStringTable qerror_table[] = {
         .desc      = "Using KVM without %(capability), %(feature) unavailable",
     },
     {
+        .error_fmt = QERR_MIGRATION_EXPECTED,
+        .desc      = "An incoming migration is expected before this command can be executed",
+    },
+    {
         .error_fmt = QERR_MISSING_PARAMETER,
         .desc      = "Parameter '%(name)' is missing",
     },