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

[Kirti Wankhede]

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 <address@hidden>
>> Signed-off-by: Neo Jia <address@hidden>
>> 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 */
>>