vhost_vdpa: fix the missing irq_bypass_unregister_producer() invocation

When qemu with vhost-vdpa netdevice is run for the first time,
it works well. But after the VM is powered off, the next qemu run
causes kernel panic due to a NULL pointer dereference in
irq_bypass_register_producer().

When the VM is powered off, vhost_vdpa_clean_irq() misses on calling
irq_bypass_unregister_producer() for irq 0 because of the existing check.

This leaves stale producer nodes, which are reset in
vhost_vring_call_reset() when vhost_dev_init() is invoked during the
second qemu run.

As the node member of struct irq_bypass_producer is also initialized
to zero, traversal on the producers list causes crash due to NULL
pointer dereference.

Fixes: 2cf1ba9a ("vhost_vdpa: implement IRQ offloading in vhost_vdpa")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211711Signed-off-by: Gautam Dawar <gdawar.xilinx@gmail.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210224114845.104173-1-gdawar.xilinx@gmail.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vdpa.c

@@ -900,14 +900,10 @@ static int vhost_vdpa_open(struct inode *inode, struct file *filep)
 
 static void vhost_vdpa_clean_irq(struct vhost_vdpa *v)
 {
-	struct vhost_virtqueue *vq;
 	int i;
 
-	for (i = 0; i < v->nvqs; i++) {
-		vq = &v->vqs[i];
-		if (vq->call_ctx.producer.irq)
-			irq_bypass_unregister_producer(&vq->call_ctx.producer);
-	}
+	for (i = 0; i < v->nvqs; i++)
+		vhost_vdpa_unsetup_vq_irq(v, i);
 }
 
 static int vhost_vdpa_release(struct inode *inode, struct file *filep)