linux-kernel - Re: [PATCH v7 04/15] s390/vfio-ap: implement in-use callback for vfio

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <458e4bfe-6736-42b5-a510-21a4594df0e1@linux.ibm.com>
Date:   Fri, 17 Apr 2020 13:23:03 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>,
        Cornelia Huck <cohuck@...hat.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ux.ibm.com, borntraeger@...ibm.com,
        mjrosato@...ux.ibm.com, pasic@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        jjherne@...ux.ibm.com, fiuczy@...ux.ibm.com
Subject: Re: [PATCH v7 04/15] s390/vfio-ap: implement in-use callback for
 vfio_ap driver



On 2020-04-16 16:45, Tony Krowiak wrote:
> 
> 
> On 4/16/20 7:18 AM, Cornelia Huck wrote:
>> On Tue,  7 Apr 2020 15:20:04 -0400
>> Tony Krowiak <akrowiak@...ux.ibm.com> wrote:
>>
>>> Let's implement the callback to indicate when an APQN
>>> is in use by the vfio_ap device driver. The callback is
>>> invoked whenever a change to the apmask or aqmask would
>>> result in one or more queue devices being removed from the driver. The
>>> vfio_ap device driver will indicate a resource is in use
>>> if the APQN of any of the queue devices to be removed are assigned to
>>> any of the matrix mdevs under the driver's control.
>>>
>>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>>> ---
>>>   drivers/s390/crypto/vfio_ap_drv.c     |  1 +
>>>   drivers/s390/crypto/vfio_ap_ops.c     | 47 +++++++++++++++++----------
>>>   drivers/s390/crypto/vfio_ap_private.h |  2 ++
>>>   3 files changed, 33 insertions(+), 17 deletions(-)
>>> @@ -1369,3 +1371,14 @@ void vfio_ap_mdev_remove_queue(struct ap_queue 
>>> *queue)
>>>       kfree(q);
>>>       mutex_unlock(&matrix_dev->lock);
>>>   }
>>> +
>>> +bool vfio_ap_mdev_resource_in_use(unsigned long *apm, unsigned long 
>>> *aqm)
>>> +{
>>> +    bool in_use;
>>> +
>>> +    mutex_lock(&matrix_dev->lock);
>>> +    in_use = vfio_ap_mdev_verify_no_sharing(NULL, apm, aqm) ? true : 
>>> false;
>> Maybe
>>
>> in_use = !!vfio_ap_mdev_verify_no_sharing(NULL, apm, aqm);
>>
>> ?
> 
> To be honest, I find the !! expression very confusing. Every time I see 
> it, I have
> to spend time thinking about what the result of !! is going to be. I think
> the statement should be left as-is because it more clearly expresses
> the intent.



In other places you use
"
         ret = vfio_ap_mdev_verify_no_sharing(matrix_mdev);
         if (ret)
                 goto share_err;
"
then why use a boolean here?

If you want to return a boolean and you do not want to use !! you can do:

  ...
   ret = vfio_ap_mdev_verify_no_sharing(NULL, apm, aqm);
...
   return (ret) ? false : true;

> 
>>
>>> +    mutex_unlock(&matrix_dev->lock);
>>> +
>>> +    return in_use;
>>> +}
> 

-- 
Pierre Morel
IBM Lab Boeblingen