In case we don't have a device for an active queue, just skip
processing the queue (same we do for inactive queues) and log
a guest bug.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
---
 hw/usb/hcd-ehci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c
index 62dab0592fa2..5f089f30054b 100644
--- a/hw/usb/hcd-ehci.c
+++ b/hw/usb/hcd-ehci.c
@@ -1834,6 +1834,9 @@ static int ehci_state_fetchqtd(EHCIQueue *q)
             ehci_set_state(q->ehci, q->async, EST_EXECUTING);
             break;
         }
+    } else if (q->dev == NULL) {
+        ehci_trace_guest_bug(q->ehci, "no device attached to queue");
+        ehci_set_state(q->ehci, q->async, EST_HORIZONTALQH);
     } else {
         p = ehci_alloc_packet(q);
         p->qtdaddr = q->qtdaddr;
-- 
2.18.1