Date:   Wed, 25 Sep 2019 20:01:24 +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,
        intel-gfx@...ts.freedesktop.org,
        intel-gvt-dev@...ts.freedesktop.org, kwankhede@...dia.com,
        mst@...hat.com, tiwei.bie@...el.com,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        cohuck@...hat.com, maxime.coquelin@...hat.com,
        cunming.liang@...el.com, zhihong.wang@...el.com,
        rob.miller@...adcom.com, xiao.w.wang@...el.com,
        haotian.wang@...ive.com, zhenyuw@...ux.intel.com,
        zhi.a.wang@...el.com, jani.nikula@...ux.intel.com,
        joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com,
        airlied@...ux.ie, daniel@...ll.ch, farman@...ux.ibm.com,
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        freude@...ux.ibm.com, lingshan.zhu@...el.com, idos@...lanox.com,
        eperezma@...hat.com, lulu@...hat.com, parav@...lanox.com,
        christophe.de.dinechin@...il.com, kevin.tian@...el.com
Subject: Re: [PATCH V2 2/8] mdev: class id support


On 2019/9/25 上午7:06, Alex Williamson wrote:
> On Tue, 24 Sep 2019 21:53:26 +0800
> Jason Wang <jasowang@...hat.com> wrote:
>
>> Mdev bus only supports vfio driver right now, so it doesn't implement
>> match method. But in the future, we may add drivers other than vfio,
>> the first driver could be virtio-mdev. This means we need to add
>> device class id support in bus match method to pair the mdev device
>> and mdev driver correctly.
>>
>> So this patch adds id_table to mdev_driver and class_id for mdev
>> parent with the match method for mdev bus.
> Description needs to be revised from v1, class_id is no longer on the
> parent.


Yes, will fix.


>> Signed-off-by: Jason Wang <jasowang@...hat.com>
>> ---
>>  Documentation/driver-api/vfio-mediated-device.rst |  3 +++
>>  drivers/gpu/drm/i915/gvt/kvmgt.c                  |  1 +
>>  drivers/s390/cio/vfio_ccw_ops.c                   |  1 +
>>  drivers/s390/crypto/vfio_ap_ops.c                 |  1 +
>>  drivers/vfio/mdev/mdev_core.c                     |  7 +++++++
>>  drivers/vfio/mdev/mdev_driver.c                   | 14 ++++++++++++++
>>  drivers/vfio/mdev/mdev_private.h                  |  1 +
>>  drivers/vfio/mdev/vfio_mdev.c                     |  6 ++++++
>>  include/linux/mdev.h                              |  8 ++++++++
>>  include/linux/mod_devicetable.h                   |  8 ++++++++
>>  samples/vfio-mdev/mbochs.c                        |  1 +
>>  samples/vfio-mdev/mdpy.c                          |  1 +
>>  samples/vfio-mdev/mtty.c                          |  1 +
>>  13 files changed, 53 insertions(+)
>>
>> diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst
>> index 25eb7d5b834b..a5bdc60d62a1 100644
>> --- a/Documentation/driver-api/vfio-mediated-device.rst
>> +++ b/Documentation/driver-api/vfio-mediated-device.rst
>> @@ -102,12 +102,14 @@ structure to represent a mediated device's driver::
>>        * @probe: called when new device created
>>        * @remove: called when device removed
>>        * @driver: device driver structure
>> +      * @id_table: the ids serviced by this driver
>>        */
>>       struct mdev_driver {
>>  	     const char *name;
>>  	     int  (*probe)  (struct device *dev);
>>  	     void (*remove) (struct device *dev);
>>  	     struct device_driver    driver;
>> +	     const struct mdev_class_id *id_table;
>>       };
>>  
>>  A mediated bus driver for mdev should use this structure in the function calls
>> @@ -165,6 +167,7 @@ register itself with the mdev core driver::
>>  	extern int  mdev_register_device(struct device *dev,
>>  	                                 const struct mdev_parent_ops *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::
> Unintended extra line?  Doesn't seem to match surrounding formatting.
>
> Calling mdev_set_class_id() as part of create seems relatively
> fundamental to the vendor driver with this change, it should be added
> to the documentation.


Right.


>
>> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
>> index 23aa3e50cbf8..f793252a3d2a 100644
>> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
>> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
>> @@ -678,6 +678,7 @@ static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev)
>>  		     dev_name(mdev_dev(mdev)));
>>  	ret = 0;
>>  
>> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>>  out:
>>  	return ret;
>>  }
>> diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
>> index f0d71ab77c50..d258ef1fedb9 100644
>> --- a/drivers/s390/cio/vfio_ccw_ops.c
>> +++ b/drivers/s390/cio/vfio_ccw_ops.c
>> @@ -129,6 +129,7 @@ static int vfio_ccw_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
>>  			   private->sch->schid.ssid,
>>  			   private->sch->schid.sch_no);
>>  
>> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>>  	return 0;
>>  }
>>  
>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
>> index 5c0f53c6dde7..2cfd96112aa0 100644
>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>> @@ -343,6 +343,7 @@ static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
>>  	list_add(&matrix_mdev->node, &matrix_dev->mdev_list);
>>  	mutex_unlock(&matrix_dev->lock);
>>  
>> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>>  	return 0;
>>  }
>>  
>> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
>> index b558d4cfd082..8764cf4a276d 100644
>> --- a/drivers/vfio/mdev/mdev_core.c
>> +++ b/drivers/vfio/mdev/mdev_core.c
>> @@ -45,6 +45,12 @@ void mdev_set_drvdata(struct mdev_device *mdev, void *data)
>>  }
>>  EXPORT_SYMBOL(mdev_set_drvdata);
>>  
>> +void mdev_set_class_id(struct mdev_device *mdev, u16 id)
>> +{
>> +	mdev->class_id = id;
>> +}
>> +EXPORT_SYMBOL(mdev_set_class_id);
>> +
>>  struct device *mdev_dev(struct mdev_device *mdev)
>>  {
>>  	return &mdev->dev;
>> @@ -135,6 +141,7 @@ static int mdev_device_remove_cb(struct device *dev, void *data)
>>   * mdev_register_device : Register a device
>>   * @dev: device structure representing parent device.
>>   * @ops: Parent device operation structure to be registered.
>> + * @id: device id.
>>   *
>>   * Add device to list of registered parent devices.
>>   * Returns a negative value on error, otherwise 0.
>> diff --git a/drivers/vfio/mdev/mdev_driver.c b/drivers/vfio/mdev/mdev_driver.c
>> index 0d3223aee20b..b7c40ce86ee3 100644
>> --- a/drivers/vfio/mdev/mdev_driver.c
>> +++ b/drivers/vfio/mdev/mdev_driver.c
>> @@ -69,8 +69,22 @@ static int mdev_remove(struct device *dev)
>>  	return 0;
>>  }
>>  
>> +static int mdev_match(struct device *dev, struct device_driver *drv)
>> +{
>> +	unsigned int i;
>> +	struct mdev_device *mdev = to_mdev_device(dev);
>> +	struct mdev_driver *mdrv = to_mdev_driver(drv);
>> +	const struct mdev_class_id *ids = mdrv->id_table;
>> +
>> +	for (i = 0; ids[i].id; i++)
>> +		if (ids[i].id == mdev->class_id)
> With the proposed API here, mdev->class_id can be NULL, do we allow
> devices to exist in that state or should mdev_device_create() generate
> an error if the .create() callback doesn't register a type?  Or a
> warn_once and assume MDEV_ID_VFIO?  The latter seems pretty sketchy
> when we get to patch 5/8.  Thanks,


It looks to me the error from mdev_device_create() is better.

Thanks


>
> Alex
>
>> +			return 1;
>> +	return 0;
>> +}
>> +
>>  struct bus_type mdev_bus_type = {
>>  	.name		= "mdev",
>> +	.match		= mdev_match,
>>  	.probe		= mdev_probe,
>>  	.remove		= mdev_remove,
>>  };
>> diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_private.h
>> index 7d922950caaf..c65f436c1869 100644
>> --- a/drivers/vfio/mdev/mdev_private.h
>> +++ b/drivers/vfio/mdev/mdev_private.h
>> @@ -33,6 +33,7 @@ struct mdev_device {
>>  	struct kobject *type_kobj;
>>  	struct device *iommu_device;
>>  	bool active;
>> +	u16 class_id;
>>  };
>>  
>>  #define to_mdev_device(dev)	container_of(dev, struct mdev_device, dev)
>> diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
>> index 30964a4e0a28..fd2a4d9a3f26 100644
>> --- a/drivers/vfio/mdev/vfio_mdev.c
>> +++ b/drivers/vfio/mdev/vfio_mdev.c
>> @@ -120,10 +120,16 @@ static void vfio_mdev_remove(struct device *dev)
>>  	vfio_del_group_dev(dev);
>>  }
>>  
>> +static struct mdev_class_id id_table[] = {
>> +	{ MDEV_ID_VFIO },
>> +	{ 0 },
>> +};
>> +
>>  static struct mdev_driver vfio_mdev_driver = {
>>  	.name	= "vfio_mdev",
>>  	.probe	= vfio_mdev_probe,
>>  	.remove	= vfio_mdev_remove,
>> +	.id_table = id_table,
>>  };
>>  
>>  static int __init vfio_mdev_init(void)
>> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
>> index 0ce30ca78db0..3974650c074f 100644
>> --- a/include/linux/mdev.h
>> +++ b/include/linux/mdev.h
>> @@ -118,6 +118,7 @@ struct mdev_type_attribute mdev_type_attr_##_name =		\
>>   * @probe: called when new device created
>>   * @remove: called when device removed
>>   * @driver: device driver structure
>> + * @id_table: the ids serviced by this driver.
>>   *
>>   **/
>>  struct mdev_driver {
>> @@ -125,12 +126,14 @@ struct mdev_driver {
>>  	int  (*probe)(struct device *dev);
>>  	void (*remove)(struct device *dev);
>>  	struct device_driver driver;
>> +	const struct mdev_class_id *id_table;
>>  };
>>  
>>  #define to_mdev_driver(drv)	container_of(drv, struct mdev_driver, driver)
>>  
>>  void *mdev_get_drvdata(struct mdev_device *mdev);
>>  void mdev_set_drvdata(struct mdev_device *mdev, void *data);
>> +void mdev_set_class_id(struct mdev_device *mdev, u16 id);
>>  const guid_t *mdev_uuid(struct mdev_device *mdev);
>>  
>>  extern struct bus_type mdev_bus_type;
>> @@ -145,4 +148,9 @@ struct device *mdev_parent_dev(struct mdev_device *mdev);
>>  struct device *mdev_dev(struct mdev_device *mdev);
>>  struct mdev_device *mdev_from_dev(struct device *dev);
>>  
>> +enum {
>> +	MDEV_ID_VFIO = 1,
>> +	/* New entries must be added here */
>> +};
>> +
>>  #endif /* MDEV_H */
>> diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
>> index 5714fd35a83c..f32c6e44fb1a 100644
>> --- a/include/linux/mod_devicetable.h
>> +++ b/include/linux/mod_devicetable.h
>> @@ -821,4 +821,12 @@ struct wmi_device_id {
>>  	const void *context;
>>  };
>>  
>> +/**
>> + * struct mdev_class_id - MDEV device class identifier
>> + * @id: Used to identify a specific class of device, e.g vfio-mdev device.
>> + */
>> +struct mdev_class_id {
>> +	__u16 id;
>> +};
>> +
>>  #endif /* LINUX_MOD_DEVICETABLE_H */
>> diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
>> index ac5c8c17b1ff..8a8583c892b2 100644
>> --- a/samples/vfio-mdev/mbochs.c
>> +++ b/samples/vfio-mdev/mbochs.c
>> @@ -561,6 +561,7 @@ static int mbochs_create(struct kobject *kobj, struct mdev_device *mdev)
>>  	mbochs_reset(mdev);
>>  
>>  	mbochs_used_mbytes += type->mbytes;
>> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>>  	return 0;
>>  
>>  err_mem:
>> diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
>> index cc86bf6566e4..88d7e76f3836 100644
>> --- a/samples/vfio-mdev/mdpy.c
>> +++ b/samples/vfio-mdev/mdpy.c
>> @@ -269,6 +269,7 @@ static int mdpy_create(struct kobject *kobj, struct mdev_device *mdev)
>>  	mdpy_reset(mdev);
>>  
>>  	mdpy_count++;
>> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>>  	return 0;
>>  }
>>  
>> diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
>> index 92e770a06ea2..4e0735143b69 100644
>> --- a/samples/vfio-mdev/mtty.c
>> +++ b/samples/vfio-mdev/mtty.c
>> @@ -770,6 +770,7 @@ static int mtty_create(struct kobject *kobj, struct mdev_device *mdev)
>>  	list_add(&mdev_state->next, &mdev_devices_list);
>>  	mutex_unlock(&mdev_list_lock);
>>  
>> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>>  	return 0;
>>  }
>>  

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