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

From: Alexey Kardashevskiy <[email-masked]>
Date: Thu, 27 Jun 2013 20:48:33 +1000

On 06/27/2013 07:42 PM, Benjamin Herrenschmidt wrote:
> 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).

I'll change to WARN_ON but...
This is going to be called on KVM exit on a file pointer previously
verified for correctness. If it is a wrong file*, then something went
terribly wrong.

-- 
Alexey