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

Cornelia Huck
2019-11-05T16:50:55Z

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 :/

> +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.