Re: [PATCH V8 3/6] mdev: introduce device specific ops

[Jason Wang <jasowang@redhat.com>]

On 2019/11/6 上午2:28, Cornelia Huck wrote:
> On Tue, 5 Nov 2019 10:44:18 -0700
> Alex Williamson <alex.williamson@redhat.com> wrote:
>
>> On Tue, 5 Nov 2019 17:50:25 +0100
>> Cornelia Huck <cohuck@redhat.com> wrote:
>>
>>> On Tue,  5 Nov 2019 17:32:37 +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.
>>>>
>>>> Reviewed-by: Parav Pandit <parav@mellanox.com>
>>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>>> ---
>>>>   .../driver-api/vfio-mediated-device.rst       | 35 +++++++++----
>>>>   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                 | 24 ++++++++-
>>>>   drivers/vfio/mdev/mdev_private.h              |  5 ++
>>>>   drivers/vfio/mdev/vfio_mdev.c                 | 37 ++++++-------
>>>>   include/linux/mdev.h                          | 43 ++++-----------
>>>>   include/linux/mdev_vfio_ops.h                 | 52 +++++++++++++++++++
>>>>   samples/vfio-mdev/mbochs.c                    | 20 ++++---
>>>>   samples/vfio-mdev/mdpy.c                      | 20 ++++---
>>>>   samples/vfio-mdev/mtty.c                      | 18 ++++---
>>>>   13 files changed, 206 insertions(+), 99 deletions(-)
>>>>   create mode 100644 include/linux/mdev_vfio_ops.h
>>>>      
>>> (...)
>>>    
>>>> @@ -172,10 +163,34 @@ that a driver should use to unregister itself with the mdev core driver::
>>>>   
>>>>   	extern void mdev_unregister_device(struct device *dev);
>>>>   
>>>> -It is also required to specify the class_id in create() callback through::
>>>> +As multiple types of mediated devices may be supported, class id needs
>>>> +to be specified in the create callback(). This could be done
>>> The brackets should probably go behind 'create'?
>>>    
>>>> +explicitly for the device that does not use on mdev bus for its
>>> "for devices that do not use the mdev bus" ?
>>>
>>> But why wouldn't they? I feel like I've missed some discussion here :/
>> The device ops provide a route through mdev-core for known callbacks,
>> which is primarily useful when we have 1:N relation between mdev bus
>> driver and vendor drivers.  The obvious example here is vfio-mdev,
>> where we have GVT-g, vfio-ap, vfio-ccw, NVIDIA GRID, and various sample
>> drivers all advertising vfio-mdev support via their class id.  However,
>> if we have a tightly coupled vendor driver and mdev bus driver, as the
>> mlx5 support that Parav is developing, the claim is that they prefer
>> not to expose any device ops and intend to interact directly with the
>> mdev device.  At least that's my understanding.  Thanks,
>>
>> Alex
> Ah, ok.
>
> So maybe use the phrasing "devices that interact with the mdev device
> directly" vs "devices that use device-specific ops" instead?
>
> Not a strong critique, though.


Will use what you suggest here.

Thanks


>
>>>> +operation through:
>>>>   
>>>>   	int mdev_set_class(struct mdev_device *mdev, u16 id);
>>>>   
>>>> +For the device that uses on the mdev bus for its operation, the
>>>> class
>>> "For devices that use the mdev bus..."
>>>
>>> But same comment as above.
>>>    
>>>> +should provide helper function to set class id and device
>>>> specific +ops. E.g for vfio-mdev devices, the function to be
>>>> called is:: +
>>>> +	int mdev_set_vfio_ops(struct mdev_device *mdev,
>>>> +                              const struct mdev_vfio_device_ops
>>>> *vfio_ops); +
>>>> +The class id (set by this function to MDEV_CLASS_ID_VFIO) is
>>>> used to +match a device with an mdev driver via its id table. The
>>>> device +specific callbacks (specified in *vfio_ops) are
>>>> obtainable via +mdev_get_vfio_ops() (for use by 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
>>>> +
>>>>   Mediated Device Management Interface Through sysfs
>>>>   ==================================================
>>> Otherwise, looks good.