Subject: Re: [PATCH 3/8] vfio: add external user support

From: Benjamin Herrenschmidt <[email-masked]>
Date: Thu, 27 Jun 2013 19:42:46 +1000

On Thu, 2013-06-27 at 16:59 +1000, Stephen Rothwell wrote:
> > +/* Allows an external user (for example, KVM) to unlock an IOMMU
> group */
> > +static void vfio_group_del_external_user(struct file *filep)
> > +{
> > +     struct vfio_group *group = filep->private_data;
> > +
> > +     BUG_ON(filep->f_op != &vfio_group_fops);
> 
> We usually reserve BUG_ON for situations where there is no way to
> continue running or continuing will corrupt the running kernel.  Maybe
> WARN_ON() and return?

Not even that. This is a user space provided "fd", we shouldn't oops the
kernel because we passed a wrong argument, just return -EINVAL or
something like that (add a return code).

Ben.