linux-kernel - Re: [PATCH v12 12/22] vfio: Add notifier callback to parent's ops structure of mdev

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Date:   Tue, 15 Nov 2016 13:41:48 +0530
From:   Kirti Wankhede <kwankhede@...dia.com>
To:     Jike Song <jike.song@...el.com>
CC:     <alex.williamson@...hat.com>, <pbonzini@...hat.com>,
        <kraxel@...hat.com>, <cjia@...dia.com>, <qemu-devel@...gnu.org>,
        <kvm@...r.kernel.org>, <kevin.tian@...el.com>,
        <bjsdjshi@...ux.vnet.ibm.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v12 12/22] vfio: Add notifier callback to parent's ops
 structure of mdev



On 11/15/2016 12:15 PM, Jike Song wrote:
> On 11/14/2016 11:42 PM, Kirti Wankhede wrote:
>> Add a notifier calback to parent's ops structure of mdev device so that per
>> device notifer for vfio module is registered through vfio_mdev module.
>>
>> Signed-off-by: Kirti Wankhede <kwankhede@...dia.com>
>> Signed-off-by: Neo Jia <cjia@...dia.com>
>> Change-Id: Iafa6f1721aecdd6e50eb93b153b5621e6d29b637
>> ---
>>  drivers/vfio/mdev/vfio_mdev.c | 19 +++++++++++++++++++
>>  include/linux/mdev.h          |  9 +++++++++
>>  2 files changed, 28 insertions(+)
>>
>> diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
>> index ffc36758cb84..1694b1635607 100644
>> --- a/drivers/vfio/mdev/vfio_mdev.c
>> +++ b/drivers/vfio/mdev/vfio_mdev.c
>> @@ -24,6 +24,15 @@
>>  #define DRIVER_AUTHOR   "NVIDIA Corporation"
>>  #define DRIVER_DESC     "VFIO based driver for Mediated device"
>>  
>> +static int vfio_mdev_notifier(struct notifier_block *nb, unsigned long action,
>> +			      void *data)
>> +{
>> +	struct mdev_device *mdev = container_of(nb, struct mdev_device, nb);
>> +	struct parent_device *parent = mdev->parent;
>> +
>> +	return parent->ops->notifier(mdev, action, data);
>> +}
>> +
>>  static int vfio_mdev_open(void *device_data)
>>  {
>>  	struct mdev_device *mdev = device_data;
>> @@ -40,6 +49,11 @@ static int vfio_mdev_open(void *device_data)
>>  	if (ret)
>>  		module_put(THIS_MODULE);
>>  
>> +	if (likely(parent->ops->notifier)) {
>> +		mdev->nb.notifier_call = vfio_mdev_notifier;
>> +		if (vfio_register_notifier(&mdev->dev, &mdev->nb))
>> +			pr_err("Failed to register notifier for mdev\n");
>> +	}
> 
> Hi Kirti,
> 
> Could you please move the notifier registration before parent->ops->open()?
> as you might know, I'm extending your vfio_register_notifier to also include
> the attaching/detaching events of vfio_group and kvm.  Basically if vfio_group
> not attached to any kvm instance, the parent->ops->open() should return -ENODEV
> to indicate the failure, but to know whether kvm is available in open(), the
> notifier registration should be earlier.
> 

Ok. That seem fine to me.

Thanks,
Kirti

> Of course I can call vfio_register_notifier() from an earlier place to
> workaround it, but it doesn't seem a canonical way.
> 
> --
> Thanks,
> Jike
> 
>>  	return ret;
>>  }
>>  
>> @@ -48,6 +62,11 @@ static void vfio_mdev_release(void *device_data)
>>  	struct mdev_device *mdev = device_data;
>>  	struct parent_device *parent = mdev->parent;
>>  
>> +	if (likely(parent->ops->notifier)) {
>> +		if (vfio_unregister_notifier(&mdev->dev, &mdev->nb))
>> +			pr_err("Failed to unregister notifier for mdev\n");
>> +	}
>> +
>>  	if (likely(parent->ops->release))
>>  		parent->ops->release(mdev);
>>  
>> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
>> index 4900cc472364..665afe0a4c31 100644
>> --- a/include/linux/mdev.h
>> +++ b/include/linux/mdev.h
>> @@ -37,6 +37,7 @@ struct mdev_device {
>>  	struct kref		ref;
>>  	struct list_head	next;
>>  	struct kobject		*type_kobj;
>> +	struct notifier_block	nb;
>>  };
>>  
>>  /**
>> @@ -85,6 +86,12 @@ struct mdev_device {
>>   * @mmap:		mmap callback
>>   *			@mdev: mediated device structure
>>   *			@vma: vma structure
>> + * @notifer:		Notifier callback, currently only for
>> + *			VFIO_IOMMU_NOTIFY_DMA_UNMAP action notified duing
>> + *			DMA_UNMAP call on mapped iova range.
>> + *			@mdev: mediated device structure
>> + *			@action: Action for which notifier is called
>> + *			@data: Data associated with the notifier
>>   * Parent device that support mediated device should be registered with mdev
>>   * module with parent_ops structure.
>>   **/
>> @@ -106,6 +113,8 @@ struct parent_ops {
>>  	ssize_t (*ioctl)(struct mdev_device *mdev, unsigned int cmd,
>>  			 unsigned long arg);
>>  	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
>> +	int	(*notifier)(struct mdev_device *mdev, unsigned long action,
>> +			    void *data);
>>  };
>>  
>>  /* interface for exporting mdev supported type attributes */
>>