linux-kernel - Re: [PATCH v3 4/9] s390: ap: tools to find a queue with a specific APQN

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Message-Id: <423e3f5b-dbbe-92b1-cfd3-d5a6f4e38f37@linux.ibm.com>
Date:   Fri, 15 Feb 2019 11:10:43 +0100
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     borntraeger@...ibm.com, alex.williamson@...hat.com,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, frankja@...ux.ibm.com, akrowiak@...ux.ibm.com,
        pasic@...ux.ibm.com, david@...hat.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, freude@...ux.ibm.com, mimu@...ux.ibm.com
Subject: Re: [PATCH v3 4/9] s390: ap: tools to find a queue with a specific
 APQN

On 15/02/2019 10:49, Cornelia Huck wrote:
> On Thu, 14 Feb 2019 14:51:04 +0100
> Pierre Morel <pmorel@...ux.ibm.com> wrote:
> 
>> We need to find the queue with a specific APQN during the
>> handling of the interception of the PQAP/AQIC instruction.
>>
>> To handle the AP associated device reference count we keep
>> track of it in the vfio_ap_queue until we put the device.
> 
> So, the relationship is
> (struct ap_device)--(driver_data)-->(struct vfio_ap_queue)--(pointer)-->(struct ap_device)
> ? IOW, a backlink?
> 
> If so, can't you already set that up during probe?

Will do.

> 
> Or am I confused by the various similar devices again? Maybe a diagram
> would help...

No you are right.


> 
>>
>> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
>> ---
>>   drivers/s390/crypto/vfio_ap_ops.c     | 54 +++++++++++++++++++++++++++++++++++
>>   drivers/s390/crypto/vfio_ap_private.h |  1 +
>>   2 files changed, 55 insertions(+)
>>
>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
>> index 900b9cf..2a52c9b 100644
>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>> @@ -24,6 +24,60 @@
>>   #define VFIO_AP_MDEV_TYPE_HWVIRT "passthrough"
>>   #define VFIO_AP_MDEV_NAME_HWVIRT "VFIO AP Passthrough Device"
>>   
>> +/**
>> + * vfio_ap_check_apqn: check if a ap_queue is of a given APQN
>> + *
>> + * Returns 1 if we have a match.
>> + * Otherwise returns 0.
>> + */
>> +static int vfio_ap_check_apqn(struct device *dev, void *data)
>> +{
>> +	struct vfio_ap_queue *q = dev_get_drvdata(dev);
>> +
>> +	return (q->apqn == *(int *)data);
>> +}
>> +
>> +/**
>> + * vfio_ap_get_queue: Retrieve a queue with a specific APQN
>> + * @apqn: The queue APQN
>> + *
>> + * Retrieve a queue with a specific APQN from the list of the
>> + * devices associated to the vfio_ap_driver.
>> + *
>> + * The vfio_ap_queue has been already associated with the device
>> + * during the probe.
>> + * Store the associated device for reference counting
>> + *
>> + * Returns the pointer to the associated vfio_ap_queue
>> + */
>> +static  __attribute__((unused))
> 
> Eww. Can you get rid of that by reordering or squashing patches?

I did this to avoid posting a very big patch.
I will of course squash 4 and 5 with patch 6, when the two patches 4 and 
5 are reviewed.

If you think it brings more clarity to squash all for the next iteration 
I will do.

Regards,
Pierre


-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany