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Reply-To: pmorel@linux.ibm.com
Subject: Re: [PATCH v8 09/22] s390: vfio-ap: register matrix device with VFIO
 mdev framework
To:     Cornelia Huck <cohuck@redhat.com>,
        Tony Krowiak <akrowiak@linux.vnet.ibm.com>
Cc:     linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, freude@de.ibm.com, schwidefsky@de.ibm.com,
        heiko.carstens@de.ibm.com, borntraeger@de.ibm.com,
        kwankhede@nvidia.com, bjsdjshi@linux.vnet.ibm.com,
        pbonzini@redhat.com, alex.williamson@redhat.com,
        pmorel@linux.vnet.ibm.com, alifm@linux.vnet.ibm.com,
        mjrosato@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com,
        thuth@redhat.com, pasic@linux.vnet.ibm.com, berrange@redhat.com,
        fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com,
        frankja@linux.ibm.com, Tony Krowiak <akrowiak@linux.ibm.com>
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 <20180809130607.32781b72.cohuck@redhat.com>
From:   Pierre Morel <pmorel@linux.ibm.com>
Date:   Thu, 9 Aug 2018 18:27:16 +0200
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On 09/08/2018 13:06, Cornelia Huck wrote:
> On Wed,  8 Aug 2018 10:44:19 -0400
> Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:
>
>> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
>> index d7e39ad..6a827f3 100644
>> --- a/drivers/s390/crypto/vfio_ap_drv.c
>> +++ b/drivers/s390/crypto/vfio_ap_drv.c
>> @@ -12,6 +12,7 @@
>>   #include <linux/mod_devicetable.h>
>>   #include <linux/slab.h>
>>   #include <linux/string.h>
>> +#include <asm/zcrypt.h>
>>   #include "vfio_ap_private.h"
>>   
>>   #define VFIO_AP_ROOT_NAME "vfio_ap"
>> @@ -68,6 +69,18 @@ static int vfio_ap_matrix_dev_create(void)
>>   {
>>   	int ret;
>>   
>> +	mutex_init(&matrix_dev.lock);
>> +	INIT_LIST_HEAD(&matrix_dev.mdev_list);
>> +
>> +	/* Test if PQAP(QCI) instruction is available */
>> +	if (test_facility(12)) {
>> +		ret = ap_qci(&matrix_dev.info);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>> +	atomic_set(&matrix_dev.available_instances, MAX_ZDEV_ENTRIES_EXT);
>> +
>>   	ret = misc_register(&matrix_dev.misc_dev);
> OK, you are adding more stuff other than the miscdevice after all...
> still, I don't think that this is a good idea.
>
> I think I had already asked this for a previous version: Why has this
> been turned into a miscdevice? (I think my reaction to the answer was
> 'meh'... but I think more and more that we should not do that.)

Following our off-line conversation...

I understand your concern, about the misc device and dynamically
updating the misc device structure.

For it is your main point of contention and we do not currently have
a use case for the misc device I propose we just let it go and
rebase on the device design we had in V6 and did not seem to
make any trouble to any one.

We will propose a v9 with the integration of all comment done
so far soon as possible.


Best regards,

Pierre


>
>>   	if (ret)
>>   		return ret;


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