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Subject: Re: [PATCH v9 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
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 <20180814131929.37d4b530.cohuck@redhat.com>
From:   Tony Krowiak <akrowiak@linux.ibm.com>
Date:   Wed, 15 Aug 2018 12:51:50 -0400
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On 08/14/2018 07:19 AM, Cornelia Huck wrote:
> On Mon, 13 Aug 2018 17:48:06 -0400
> Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:
>
>> From: Tony Krowiak <akrowiak@linux.ibm.com>
>>
>> Registers the matrix device created by the VFIO AP device
>> driver with the VFIO mediated device framework.
>> Registering the matrix device will create the sysfs
>> structures needed to create mediated matrix devices
>> each of which will be used to configure the AP matrix
>> for a guest and connect it to the VFIO AP device driver.
>>
>> Registering the matrix device with the VFIO mediated device
>> framework will create the following sysfs structures:
>>
>> /sys/devices/vfio_ap/matrix/
>> ...... [mdev_supported_types]
>> ......... [vfio_ap-passthrough]
>> ............ create
>>
>> To create a mediated device for the AP matrix device, write a UUID
>> to the create file:
>>
>> 	uuidgen > create
>>
>> A symbolic link to the mediated device's directory will be created in the
>> devices subdirectory named after the generated $uuid:
>>
>> /sys/devices/vfio_ap/matrix/
>> ...... [mdev_supported_types]
>> ......... [vfio_ap-passthrough]
>> ............ [devices]
>> ............... [$uuid]
>>
>> A symbolic link to the mediated device will also be created
>> in the vfio_ap matrix's directory:
>>
>> /sys/devices/vfio_ap/matrix/[$uuid]
>>
>> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
>> Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
>> Tested-by: Michael Mueller <mimu@linux.ibm.com>
>> Tested-by: Farhan Ali <alifm@linux.ibm.com>
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> ---
>>   MAINTAINERS                           |    1 +
>>   drivers/s390/crypto/Makefile          |    2 +-
>>   drivers/s390/crypto/vfio_ap_drv.c     |   23 ++++++
>>   drivers/s390/crypto/vfio_ap_ops.c     |  124 +++++++++++++++++++++++++++++++++
>>   drivers/s390/crypto/vfio_ap_private.h |   45 ++++++++++++
>>   include/uapi/linux/vfio.h             |    1 +
>>   6 files changed, 195 insertions(+), 1 deletions(-)
>>   create mode 100644 drivers/s390/crypto/vfio_ap_ops.c
>>
>
>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
>> new file mode 100644
>> index 0000000..8018c2d
>> --- /dev/null
>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>> @@ -0,0 +1,124 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +/*
>> + * Adjunct processor matrix VFIO device driver callbacks.
>> + *
>> + * Copyright IBM Corp. 2018
>> + *
>> + * Author(s): Tony Krowiak <akrowiak@linux.ibm.com>
>> + *	      Halil Pasic <pasic@linux.ibm.com>
>> + *	      Pierre Morel <pmorel@linux.ibm.com>
>> + */
>> +#include <linux/string.h>
>> +#include <linux/vfio.h>
>> +#include <linux/device.h>
>> +#include <linux/list.h>
>> +#include <linux/ctype.h>
>> +
>> +#include "vfio_ap_private.h"
>> +
>> +#define VFIO_AP_MDEV_TYPE_HWVIRT "passthrough"
>> +#define VFIO_AP_MDEV_NAME_HWVIRT "VFIO AP Passthrough Device"
>> +
>> +static void vfio_ap_matrix_init(struct ap_config_info *info,
>> +				struct ap_matrix *matrix)
>> +{
>> +	matrix->apm_max = info->apxa ? info->Na : 63;
>> +	matrix->aqm_max = info->apxa ? info->Nd : 15;
>> +	matrix->adm_max = info->apxa ? info->Nd : 15;
>> +}
>> +
>> +static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
>> +{
>> +	struct ap_matrix_mdev *matrix_mdev;
>> +
>> +	matrix_mdev = kzalloc(sizeof(*matrix_mdev), GFP_KERNEL);
>> +	if (!matrix_mdev)
>> +		return -ENOMEM;
>> +
>> +	matrix_mdev->name = dev_name(mdev_dev(mdev));
>> +	vfio_ap_matrix_init(&matrix_dev.info, &matrix_mdev->matrix);
>> +	mdev_set_drvdata(mdev, matrix_mdev);
>> +
>> +	if (atomic_dec_if_positive(&matrix_dev.available_instances) < 0) {
>> +		kfree(matrix_mdev);
>> +		return -EPERM;
>> +	}
> Maybe move this check to the top of the function?

I am going to remove this check. Since we have added a mutex to lock the
matrix_dev, I see no need for the available_instances to be an atomic_t
type because we can update it while holding the matrix_dev lock when the
other updates are made to the matrix_dev.

>
>> +
>> +	mutex_lock(&matrix_dev.lock);
>> +	list_add(&matrix_mdev->list, &matrix_dev.mdev_list);
>> +	mutex_unlock(&matrix_dev.lock);
>> +
>> +	return 0;
>> +}