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

Jason Wang
2019-10-18T07:35:18Z

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).