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

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Message-ID: <20191105175025.1a620844.cohuck@redhat.com>
Date:   Tue, 5 Nov 2019 17:50:25 +0100
From:   Cornelia Huck <cohuck@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     kvm@...r.kernel.org, linux-s390@...r.kernel.org,
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Subject: Re: [PATCH V8 3/6] mdev: introduce device specific ops

On Tue,  5 Nov 2019 17:32:37 +0800
Jason Wang <jasowang@...hat.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@...lanox.com>
> Signed-off-by: Jason Wang <jasowang@...hat.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.