Date:   Wed, 25 Sep 2019 20:04:54 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
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Subject: Re: [PATCH V2 5/8] mdev: introduce device specific ops


On 2019/9/25 上午7:06, Alex Williamson wrote:
> On Tue, 24 Sep 2019 21:53:29 +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.
>>
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
>> ---
>>  .../driver-api/vfio-mediated-device.rst       |  4 +-
>>  MAINTAINERS                                   |  1 +
>>  drivers/gpu/drm/i915/gvt/kvmgt.c              | 17 +++---
>>  drivers/s390/cio/vfio_ccw_ops.c               | 17 ++++--
>>  drivers/s390/crypto/vfio_ap_ops.c             | 13 +++--
>>  drivers/vfio/mdev/mdev_core.c                 | 12 +++++
>>  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                    | 19 ++++---
>>  samples/vfio-mdev/mdpy.c                      | 19 ++++---
>>  samples/vfio-mdev/mtty.c                      | 17 ++++--
>>  13 files changed, 168 insertions(+), 83 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 a5bdc60d62a1..d50425b368bb 100644
>> --- a/Documentation/driver-api/vfio-mediated-device.rst
>> +++ b/Documentation/driver-api/vfio-mediated-device.rst
>> @@ -152,7 +152,9 @@ 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:
>> +The device specific callbacks are referred through device_ops pointer
>> +in mdev_parent_ops. For vfio-mdev device, its callbacks in device_ops
>> +are as follows:
> This is not accurate.  device_ops is now on the mdev_device and is an
> mdev bus driver specific structure of callbacks that must be registered
> for each mdev device by the parent driver during the create callback.
> There's a one to one mapping of class_id to mdev_device_ops callbacks.


Yes.


>
> That also suggests to me that we could be more clever in registering
> both of these with mdev-core.  Can we embed the class_id in the ops
> structure in a common way so that the core can extract it and the bus
> drivers can access their specific callbacks?


That seems much cleaner, let me try to do that in V3.


>
>>  * open: open callback of mediated device
>>  * close: close callback of mediated device
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index b2326dece28e..89832b316500 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -17075,6 +17075,7 @@ S:	Maintained
>>  F:	Documentation/driver-api/vfio-mediated-device.rst
>>  F:	drivers/vfio/mdev/
>>  F:	include/linux/mdev.h
>> +F:	include/linux/vfio_mdev.h
>>  F:	samples/vfio-mdev/
>>  
>>  VFIO PLATFORM DRIVER
>> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
>> index f793252a3d2a..b274f5ee481f 100644
>> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
>> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
>> @@ -42,6 +42,7 @@
>>  #include <linux/kvm_host.h>
>>  #include <linux/vfio.h>
>>  #include <linux/mdev.h>
>> +#include <linux/vfio_mdev.h>
>>  #include <linux/debugfs.h>
>>  
>>  #include <linux/nospec.h>
>> @@ -643,6 +644,8 @@ static void kvmgt_put_vfio_device(void *vgpu)
>>  	vfio_device_put(((struct intel_vgpu *)vgpu)->vdev.vfio_device);
>>  }
>>  
>> +static struct vfio_mdev_device_ops intel_vfio_vgpu_dev_ops;
>> +
>>  static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev)
>>  {
>>  	struct intel_vgpu *vgpu = NULL;
>> @@ -679,6 +682,7 @@ static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev)
>>  	ret = 0;
>>  
>>  	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>> +	mdev_set_dev_ops(mdev, &intel_vfio_vgpu_dev_ops);
> This seems rather unrefined.  We're registering interdependent data in
> separate calls.  All drivers need to make both of these calls.  I'm not
> sure if this is a good idea, but what if we had:
>
> static const struct vfio_mdev_device_ops intel_vfio_vgpu_dev_ops = {
> 	.id			= MDEV_ID_VFIO,
>  	.open			= intel_vgpu_open,
>  	.release		= intel_vgpu_release,
>         ...
>
> And the set function passed &intel_vfio_vgpu_dev_ops.id and the mdev
> bus drivers used container_of to get to their callbacks?


Yes, with the check of mdev_device_create() if nothing is set by the device.


>
>>  out:
>>  	return ret;
>>  }
>> @@ -1601,20 +1605,21 @@ static const struct attribute_group *intel_vgpu_groups[] = {
>>  	NULL,
>>  };
>>  
>> -static struct mdev_parent_ops intel_vgpu_ops = {
>> -	.mdev_attr_groups       = intel_vgpu_groups,
>> -	.create			= intel_vgpu_create,
>> -	.remove			= intel_vgpu_remove,
>> -
>> +static struct vfio_mdev_device_ops intel_vfio_vgpu_dev_ops = {
>>  	.open			= intel_vgpu_open,
>>  	.release		= intel_vgpu_release,
>> -
>>  	.read			= intel_vgpu_read,
>>  	.write			= intel_vgpu_write,
>>  	.mmap			= intel_vgpu_mmap,
>>  	.ioctl			= intel_vgpu_ioctl,
>>  };
>>  
>> +static struct mdev_parent_ops intel_vgpu_ops = {
> These could maybe be made const at the same time.  Thanks,
>
> Alex


Ok, let me fix.

Thanks

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