Re: [PATCH V4 3/6] mdev: introduce device specific ops

[Jason Wang <jasowang@redhat.com>]

On 2019/10/17 下午11:07, Cornelia Huck wrote:
> On Thu, 17 Oct 2019 18:48:33 +0800
> Jason Wang <jasowang@redhat.com> wrote:
>
>> Currently, except for the create and remove, the rest of
>> mdev_parent_ops is designed for vfio-mdev driver only and may not help
>> for kernel mdev driver. With the help of class id, this patch
>> introduces device specific callbacks inside mdev_device
>> structure. This allows different set of callback to be used by
>> vfio-mdev and virtio-mdev.
>>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> ---
>>   .../driver-api/vfio-mediated-device.rst       | 25 +++++----
>>   MAINTAINERS                                   |  1 +
>>   drivers/gpu/drm/i915/gvt/kvmgt.c              | 18 ++++---
>>   drivers/s390/cio/vfio_ccw_ops.c               | 18 ++++---
>>   drivers/s390/crypto/vfio_ap_ops.c             | 14 +++--
>>   drivers/vfio/mdev/mdev_core.c                 | 18 +++++--
>>   drivers/vfio/mdev/mdev_private.h              |  1 +
>>   drivers/vfio/mdev/vfio_mdev.c                 | 37 ++++++-------
>>   include/linux/mdev.h                          | 45 ++++------------
>>   include/linux/vfio_mdev.h                     | 52 +++++++++++++++++++
>>   samples/vfio-mdev/mbochs.c                    | 20 ++++---
>>   samples/vfio-mdev/mdpy.c                      | 20 ++++---
>>   samples/vfio-mdev/mtty.c                      | 18 ++++---
>>   13 files changed, 184 insertions(+), 103 deletions(-)
>>   create mode 100644 include/linux/vfio_mdev.h
>>
>> diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst
>> index f9a78d75a67a..0cca84d19603 100644
>> --- a/Documentation/driver-api/vfio-mediated-device.rst
>> +++ b/Documentation/driver-api/vfio-mediated-device.rst
>> @@ -152,11 +152,22 @@ callbacks per mdev parent device, per mdev type, or any other categorization.
>>   Vendor drivers are expected to be fully asynchronous in this respect or
>>   provide their own internal resource protection.)
>>   
>> -The callbacks in the mdev_parent_ops structure are as follows:
>> -
>> -* open: open callback of mediated device
>> -* close: close callback of mediated device
>> -* ioctl: ioctl callback of mediated device
>> +As multiple types of mediated devices may be supported, the device
>> +must set up the class id and the device specific callbacks in create()
> s/in create()/in the create()/


Will fix.


>
>> +callback. E.g for vfio-mdev device it needs to be done through:
> "Each class provides a helper function to do so; e.g. for vfio-mdev
> devices, the function to be called is:"
>
> ?


This looks better.


>
>> +
>> +    int mdev_set_vfio_ops(struct mdev_device *mdev,
>> +                          const struct vfio_mdev_ops *vfio_ops);
>> +
>> +The class id (set to MDEV_CLASS_ID_VFIO) is used to match a device
> "(set by this helper function to MDEV_CLASS_ID_VFIO)" ?


Yes.


>> +with an mdev driver via its id table. The device specific callbacks
>> +(specified in *ops) are obtainable via mdev_get_dev_ops() (for use by
> "(specified in *vfio_ops by the caller)" ?


Yes.


>> +the mdev bus driver). A vfio-mdev device (class id MDEV_CLASS_ID_VFIO)
>> +uses the following device-specific ops:
>> +
>> +* open: open callback of vfio mediated device
>> +* close: close callback of vfio mediated device
>> +* ioctl: ioctl callback of vfio mediated device
>>   * read : read emulation callback
>>   * write: write emulation callback
>>   * mmap: mmap emulation callback
>> @@ -167,10 +178,6 @@ register itself with the mdev core driver::
>>   	extern int  mdev_register_device(struct device *dev,
>>   	                                 const struct mdev_parent_ops *ops);
>>   
>> -It is also required to specify the class_id in create() callback through::
>> -
>> -	int mdev_set_class(struct mdev_device *mdev, u16 id);
>> -
> I'm wondering if this patch set should start out with introducing
> helper functions already (i.e. don't introduce mdev_set_class(), but
> start out with mdev_set_class_vfio() which will gain the *vfio_ops
> argument in this patch.)


I think it doesn't harm to keep it as is since in patch 1 we introduce 
class_id and bus match method based on that without device ops there.  
But if you stick I can change.

Thanks


>
>>   However, the mdev_parent_ops structure is not required in the function call
>>   that a driver should use to unregister itself with the mdev core driver::
>>   
> (...)
>
>> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
>> index 3a9c52d71b4e..d0f3113c8071 100644
>> --- a/drivers/vfio/mdev/mdev_core.c
>> +++ b/drivers/vfio/mdev/mdev_core.c
>> @@ -45,15 +45,23 @@ void mdev_set_drvdata(struct mdev_device *mdev, void *data)
>>   }
>>   EXPORT_SYMBOL(mdev_set_drvdata);
>>   
>> -/* Specify the class for the mdev device, this must be called during
>> - * create() callback.
>> +/* Specify the VFIO device ops for the mdev device, this
>> + * must be called during create() callback for VFIO mdev device.
>>    */
> /*
>   * Specify the mdev device to be a VFIO mdev device, and set the
>   * VFIO devices ops for it. This must be called from the create()
>   * callback for VFIO mdev devices.
>   */
>
> ?
>
>> -void mdev_set_class(struct mdev_device *mdev, u16 id)
>> +void mdev_set_vfio_ops(struct mdev_device *mdev,
>> +		       const struct vfio_mdev_device_ops *vfio_ops)
>>   {
>>   	WARN_ON(mdev->class_id);
>> -	mdev->class_id = id;
>> +	mdev->class_id = MDEV_CLASS_ID_VFIO;
>> +	mdev->device_ops = vfio_ops;
>>   }
>> -EXPORT_SYMBOL(mdev_set_class);
>> +EXPORT_SYMBOL(mdev_set_vfio_ops);
>> +
>> +const void *mdev_get_dev_ops(struct mdev_device *mdev)
>> +{
>> +	return mdev->device_ops;
>> +}
>> +EXPORT_SYMBOL(mdev_get_dev_ops);
>>   
>>   struct device *mdev_dev(struct mdev_device *mdev)
>>   {
> (...)
>
> The code change looks good to me; I'm just wondering if we should
> introduce mdev_set_class() at all (see above).