vhost_vdpa: don't setup irq offloading when irq_num < 0

When irq number is negative(e.g., -EINVAL), the virtqueue
may be disabled or the virtqueues are sharing a device irq.
In such case, we should not setup irq offloading for a virtqueue.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Link: https://lore.kernel.org/r/20220222115428.998334-3-lingshan.zhu@intel.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vdpa.c

@@ -97,8 +97,11 @@ static void vhost_vdpa_setup_vq_irq(struct vhost_vdpa *v, u16 qid)
 		return;
 
 	irq = ops->get_vq_irq(vdpa, qid);
+	if (irq < 0)
+		return;
+
 	irq_bypass_unregister_producer(&vq->call_ctx.producer);
-	if (!vq->call_ctx.ctx || irq < 0)
+	if (!vq->call_ctx.ctx)
 		return;
 
 	vq->call_ctx.producer.token = vq->call_ctx.ctx;