virtio-scsi: dataplane: stop trying on notifier error

There's no use to constantly trying to enable dataplane if we failed
to set up guest or host notifiers, so fence it off in that case.
We'll try again if the device is reinitialized.
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/scsi/virtio-scsi-dataplane.c

@@ -53,6 +53,7 @@ static VirtIOSCSIVring *virtio_scsi_vring_init(VirtIOSCSI *s,
     if (rc != 0) {
         fprintf(stderr, "virtio-scsi: Failed to set host notifier (%d)\n",
                 rc);
+        s->dataplane_fenced = true;
         return NULL;
     }
     r->host_notifier = *virtio_queue_get_host_notifier(vq);
@@ -198,6 +199,7 @@ void virtio_scsi_dataplane_start(VirtIOSCSI *s)
 
     if (s->dataplane_started ||
         s->dataplane_starting ||
+        s->dataplane_fenced ||
         s->ctx != iothread_get_aio_context(vs->conf.iothread)) {
         return;
     }
@@ -211,6 +213,7 @@ void virtio_scsi_dataplane_start(VirtIOSCSI *s)
     if (rc != 0) {
         fprintf(stderr, "virtio-scsi: Failed to set guest notifiers (%d), "
                 "ensure -enable-kvm is set\n", rc);
+        s->dataplane_fenced = true;
         goto fail_guest_notifiers;
     }
 
@@ -262,6 +265,11 @@ void virtio_scsi_dataplane_stop(VirtIOSCSI *s)
     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
     int i;
 
+    /* Better luck next time. */
+    if (s->dataplane_fenced) {
+        s->dataplane_fenced = false;
+        return;
+    }
     if (!s->dataplane_started || s->dataplane_stopping) {
         return;
     }

include/hw/virtio/virtio-scsi.h

@@ -195,6 +195,7 @@ typedef struct VirtIOSCSI {
     bool dataplane_starting;
     bool dataplane_stopping;
     bool dataplane_disabled;
+    bool dataplane_fenced;
     Error *blocker;
     Notifier migration_state_notifier;
 } VirtIOSCSI;