Re: [PATCH V2 5/8] mdev: introduce device specific ops

Jason Wang
2019-09-25T12:04:54Z

On 2019/9/25 上午7:06, Alex Williamson wrote:
> On Tue, 24 Sep 2019 21:53:29 +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.
>>
>> Signed-off-by: Jason Wang <jasowang@redhat.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