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

[Jason Wang]

On 2019/10/15 äå6:41, Cornelia Huck wrote:
> On Fri, 11 Oct 2019 16:15:54 +0800
> Jason Wang <jasowang@xxxxxxxxxx> 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@xxxxxxxxxx>
> > ---
> >   .../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::