linux-kernel - Re: [PATCH v16 02/14] s390/vfio-ap: use new AP bus interface to search for queue devices

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Date:   Wed, 9 Jun 2021 14:23:44 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     jjherne@...ux.ibm.com, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     freude@...ux.ibm.com, borntraeger@...ibm.com, cohuck@...hat.com,
        mjrosato@...ux.ibm.com, pasic@...ux.ibm.com,
        alex.williamson@...hat.com, kwankhede@...dia.com,
        fiuczy@...ux.ibm.com
Subject: Re: [PATCH v16 02/14] s390/vfio-ap: use new AP bus interface to
 search for queue devices



On 6/9/21 9:52 AM, Jason J. Herne wrote:
> On 5/10/21 12:44 PM, Tony Krowiak wrote:
>> This patch refactors the vfio_ap device driver to use the AP bus's
>> ap_get_qdev() function to retrieve the vfio_ap_queue struct containing
>> information about a queue that is bound to the vfio_ap device driver.
>> The bus's ap_get_qdev() function retrieves the queue device from a
>> hashtable keyed by APQN. This is much more efficient than looping over
>> the list of devices attached to the AP bus by several orders of
>> magnitude.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>> Reviewed-by: Halil Pasic <pasic@...ux.ibm.com>
>> ---
>>   drivers/s390/crypto/vfio_ap_ops.c | 23 +++++++++--------------
>>   1 file changed, 9 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c 
>> b/drivers/s390/crypto/vfio_ap_ops.c
>> index 757166da947e..8a50aa650b65 100644
>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>> @@ -27,13 +27,6 @@
>>   static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev);
>>   static struct vfio_ap_queue *vfio_ap_find_queue(int apqn);
>>   -static int match_apqn(struct device *dev, const void *data)
>> -{
>> -    struct vfio_ap_queue *q = dev_get_drvdata(dev);
>> -
>> -    return (q->apqn == *(int *)(data)) ? 1 : 0;
>> -}
>> -
>>   /**
>>    * vfio_ap_get_queue: Retrieve a queue with a specific APQN from a 
>> list
>>    * @matrix_mdev: the associated mediated matrix
>> @@ -1253,15 +1246,17 @@ static int vfio_ap_mdev_group_notifier(struct 
>> notifier_block *nb,
>>     static struct vfio_ap_queue *vfio_ap_find_queue(int apqn)
>>   {
>> -    struct device *dev;
>> +    struct ap_queue *queue;
>>       struct vfio_ap_queue *q = NULL;
>
> The use of q and queue as variable names was a little confusing to me 
> at first. I tried renaming them a few times, the best I could come up 
> with was this:

I am (was) not a fan of the naming convention, but using 'q' to name a 
struct vfio_ap_queue
was introduced (not by me) quite some time ago, so rather than 
introducing a variable name
change at this juncture, I stuck with it to be consistent with the other 
places it is used.

>
> struct ap_queue *queue;
> struct vfio_ap_queue *vfio_queue = NULL;
>
> Take it or leave it :) Other than that, LGTM.
> Reviewed-by: Jason J. Herne <jjherne@...ux.ibm.com>

Thanks for your review.

>
>
>> -    dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL,
>> -                 &apqn, match_apqn);
>> -    if (dev) {
>> -        q = dev_get_drvdata(dev);
>> -        put_device(dev);
>> -    }
>> +    queue = ap_get_qdev(apqn);
>> +    if (!queue)
>> +        return NULL;
>> +
>> +    if (queue->ap_dev.device.driver == 
>> &matrix_dev->vfio_ap_drv->driver)
>> +        q = dev_get_drvdata(&queue->ap_dev.device);
>> +
>> +    put_device(&queue->ap_dev.device);
>>         return q;
>>   }
>>
>
>