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

[Jike Song]

On 11/15/2016 04:11 PM, Kirti Wankhede wrote:
> 
> 
> 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 - and I guess it's also good to move unregister after ->release(),
so that a sequence of register-open-release-unregister guaranteed :)

--
Thanks,
Jike