Re: [PATCH V3 4/7] mdev: introduce device specific ops

Jason Wang
2019-10-15T12:17:01Z

On 2019/10/15 下午6:41, Cornelia Huck wrote:
> On Fri, 11 Oct 2019 16:15:54 +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 | 22 +++++---
>> 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 | 9 +++-
>> drivers/vfio/mdev/mdev_private.h | 1 +
>> drivers/vfio/mdev/vfio_mdev.c | 37 ++++++-------
>> include/linux/mdev.h | 42 +++------------
>> include/linux/vfio_mdev.h | 52 +++++++++++++++++++
>> samples/vfio-mdev/mbochs.c | 20 ++++---
>> samples/vfio-mdev/mdpy.c | 21 +++++---
>> samples/vfio-mdev/mtty.c | 18 ++++---
>> 13 files changed, 177 insertions(+), 96 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 2035e48da7b2..553574ebba73 100644
>> --- a/Documentation/driver-api/vfio-mediated-device.rst
>> +++ b/Documentation/driver-api/vfio-mediated-device.rst
>> @@ -152,11 +152,20 @@ 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:
>> +In order to support multiple types of device/driver, device needs to
>> +provide both class_id and device_ops through:
> "As multiple types of mediated devices may be supported, the device
> needs to set up the class id and the device specific callbacks via:"
>
> ?
>
>>
>> -* open: open callback of mediated device
>> -* close: close callback of mediated device
>> -* ioctl: ioctl callback of mediated device
>> + void mdev_set_class(struct mdev_device *mdev, u16 id, const void *ops);
>> +
>> +The class_id is used to be paired with ids in id_table in mdev_driver
>> +structure for probing the correct driver.
> "The class id (specified in id) is used to match a device with an mdev
> driver via its id table."
>
> ?
>
>> The device_ops is device
>> +specific callbacks which can be get through mdev_get_dev_ops()
>> +function by mdev bus driver.
> "The device specific callbacks (specified in *ops) are obtainable via
> mdev_get_dev_ops() (for use by the mdev bus driver.)"
>
> ?
>
>> For vfio-mdev device, its device specific
>> +ops are as follows:
> "A vfio-mdev device (class id MDEV_ID_VFIO) uses the following
> device-specific ops:"
>
> ?

All you propose is better than what I wrote, will change the docs.

>
>> +
>> +* 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
>> @@ -167,9 +176,10 @@ 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 through::
>> +It is also required to specify the class_id and device specific ops through::
>>
>> - extern int mdev_set_class(struct device *dev, u16 id);
>> + extern int mdev_set_class(struct device *dev, u16 id,
>> + const void *ops);
> Apologies if that has already been discussed, but do we want a 1:1
> relationship between id and ops, or can different devices with the same
> id register different ops?

I think we have a N:1 mapping between id and ops, e.g we want both
virtio-mdev and vhost-mdev use a single set of device ops.

Thanks

> If the former, would it make sense to first
> register the ops for an id (once), and then have the ->create callback
> only set the class id (with the core doing the lookup of the ops)?
>
>>
>> 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::