[PATCH V7 4/6] mdev: introduce virtio device and its device ops

Jason Wang jasowang at redhat.com
Tue Nov 5 03:52:41 UTC 2019


On 2019/11/5 上午5:50, Alex Williamson wrote:
> On Mon,  4 Nov 2019 20:39:50 +0800
> Jason Wang <jasowang at redhat.com> wrote:
>
>> This patch implements basic support for mdev driver that supports
>> virtio transport for kernel virtio driver.
>>
>> Signed-off-by: Jason Wang <jasowang at redhat.com>
>> ---
>>   drivers/vfio/mdev/mdev_core.c    |  20 ++++
>>   drivers/vfio/mdev/mdev_private.h |   2 +
>>   include/linux/mdev.h             |   6 ++
>>   include/linux/mdev_virtio_ops.h  | 166 +++++++++++++++++++++++++++++++
>>   4 files changed, 194 insertions(+)
>>   create mode 100644 include/linux/mdev_virtio_ops.h
>>
>> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
>> index 8d579d7ed82f..95ee4126ff9c 100644
>> --- a/drivers/vfio/mdev/mdev_core.c
>> +++ b/drivers/vfio/mdev/mdev_core.c
>> @@ -76,6 +76,26 @@ const struct mdev_vfio_device_ops *mdev_get_vfio_ops(struct mdev_device *mdev)
>>   }
>>   EXPORT_SYMBOL(mdev_get_vfio_ops);
>>   
>> +/* Specify the virtio device ops for the mdev device, this
>> + * must be called during create() callback for virtio mdev device.
>> + */
> Comment style.


Will fix.


>
>> +void mdev_set_virtio_ops(struct mdev_device *mdev,
>> +			 const struct mdev_virtio_device_ops *virtio_ops)
>> +{
>> +	mdev_set_class(mdev, MDEV_CLASS_ID_VIRTIO);
>> +	mdev->virtio_ops = virtio_ops;
>> +}
>> +EXPORT_SYMBOL(mdev_set_virtio_ops);
>> +
>> +/* Get the virtio device ops for the mdev device. */
>> +const struct mdev_virtio_device_ops *
>> +mdev_get_virtio_ops(struct mdev_device *mdev)
>> +{
>> +	WARN_ON(mdev->class_id != MDEV_CLASS_ID_VIRTIO);
>> +	return mdev->virtio_ops;
>> +}
>> +EXPORT_SYMBOL(mdev_get_virtio_ops);
>> +
>>   struct device *mdev_dev(struct mdev_device *mdev)
>>   {
>>   	return &mdev->dev;
>> diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_private.h
>> index 411227373625..2c74dd032409 100644
>> --- a/drivers/vfio/mdev/mdev_private.h
>> +++ b/drivers/vfio/mdev/mdev_private.h
>> @@ -11,6 +11,7 @@
>>   #define MDEV_PRIVATE_H
>>   
>>   #include <linux/mdev_vfio_ops.h>
>> +#include <linux/mdev_virtio_ops.h>
>>   
>>   int  mdev_bus_register(void);
>>   void mdev_bus_unregister(void);
>> @@ -38,6 +39,7 @@ struct mdev_device {
>>   	u16 class_id;
>>   	union {
>>   		const struct mdev_vfio_device_ops *vfio_ops;
>> +		const struct mdev_virtio_device_ops *virtio_ops;
>>   	};
>>   };
>>   
>> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
>> index 9e37506d1987..f3d75a60c2b5 100644
>> --- a/include/linux/mdev.h
>> +++ b/include/linux/mdev.h
>> @@ -17,6 +17,7 @@
>>   
>>   struct mdev_device;
>>   struct mdev_vfio_device_ops;
>> +struct mdev_virtio_device_ops;
>>   
>>   /*
>>    * Called by the parent device driver to set the device which represents
>> @@ -112,6 +113,10 @@ void mdev_set_class(struct mdev_device *mdev, u16 id);
>>   void mdev_set_vfio_ops(struct mdev_device *mdev,
>>   		       const struct mdev_vfio_device_ops *vfio_ops);
>>   const struct mdev_vfio_device_ops *mdev_get_vfio_ops(struct mdev_device *mdev);
>> +void mdev_set_virtio_ops(struct mdev_device *mdev,
>> +			 const struct mdev_virtio_device_ops *virtio_ops);
>> +const struct mdev_virtio_device_ops *
>> +mdev_get_virtio_ops(struct mdev_device *mdev);
>>   
>>   extern struct bus_type mdev_bus_type;
>>   
>> @@ -127,6 +132,7 @@ struct mdev_device *mdev_from_dev(struct device *dev);
>>   
>>   enum {
>>   	MDEV_CLASS_ID_VFIO = 1,
>> +	MDEV_CLASS_ID_VIRTIO = 2,
>>   	/* New entries must be added here */
>>   };
>>   
>> diff --git a/include/linux/mdev_virtio_ops.h b/include/linux/mdev_virtio_ops.h
>> new file mode 100644
>> index 000000000000..0dcae7fa31e5
>> --- /dev/null
>> +++ b/include/linux/mdev_virtio_ops.h
>> @@ -0,0 +1,166 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Virtio mediated device driver
>> + *
>> + * Copyright 2019, Red Hat Corp.
>> + *     Author: Jason Wang <jasowang at redhat.com>
>> + */
>> +#ifndef MDEV_VIRTIO_OPS_H
>> +#define MDEV_VIRTIO_OPS_H
>> +
>> +#include <linux/interrupt.h>
>> +#include <linux/mdev.h>
>> +#include <uapi/linux/vhost.h>
>> +
>> +#define VIRTIO_MDEV_DEVICE_API_STRING		"virtio-mdev"
>> +#define VIRTIO_MDEV_F_VERSION_1 0x1
>> +
>> +struct virtio_mdev_callback {
>> +	irqreturn_t (*callback)(void *data);
>> +	void *private;
>> +};
>> +
>> +/**
>> + * struct mdev_virtio_device_ops - Structure to be registered for each
>> + * mdev device to register the device for virtio/vhost drivers.
>> + *
>> + * The device ops that is supported by VIRTIO_MDEV_F_VERSION_1, the
>> + * callbacks are mandatory unless explicity mentioned.
>> + *
>> + * @get_mdev_features:		Get a set of bits that demonstrate
>> + *				the capability of the mdev device. New
>> + *				feature bits must be added when
>> + *				introducing new device ops. This
>> + *				allows the device ops to be extended
>> + *				(one feature could have N new ops).
>> + *				@mdev: mediated device
>> + *				Returns the mdev features (API) support by
>> + *				the device.
> I still don't see the point of VIRTIO_MDEV_F_VERSION_1.  In what case
> would it not be set?


It's a must for current driver implementation.


> What would it indicate to the caller if it were
> not set?  The existence of this interface seems to indicate version 1.


The idea is when VIRTIO_MDE_F_VERSION_1 is advertised, driver will 
assume all the mandatory callbacks for this feature were implemented. 
Then there's no need to check the existence of each callback.


>
> I'm also still unclear how device ops gets extended, can you give some
> examples?  Particularly, if feature A and feature B both add device ops
> callbacks, is the vendor allowed to support B but not A, and does that
> imply their device ops structure includes callbacks for A but they're
> unused?


For current API, the answer is yes. So if vendor only support feature B, 
it needs to set the device_ops that support feature A to NULL.


> Why doesn't the previous patch take any of this into account
> for struct mdev_vfio_device_ops?  I think this is an internal API,
> therefore is it worthwhile to include feature and extension support?


I'm not sure if VFIO has the request. In that case new features could be 
extended simply through transport/bus specific way (e.g PCIE capability 
list). But in the case of virtio-mdev, we need invent something on our 
own. If the simple mapping between features and device ops is proved to 
be not sufficient or sub-optimal, we can introduce a more sophisticated 
API.


>
>> + * @get_mdev_features:		Set a set of features that will be
> s/get/set/


Will fix.


>
>> + *				used by the driver.
>> + *				@features: features used by the driver
>> + *				Returns bollean: whether the features
> s/bollean/boolean/
>
> How does one provide a set of features to set given this prototype?
>
> bool (*set_mdev_feature)(struct mdev_device *mdev);
>
> This is starting to look like a grab bag of callbacks, what sort of
> mdev features would the driver have the ability to set on a device?


Yes, e.g device support A,B,C, but driver will only use B and C.


>
> Note that this is not listed as optional, but the sample driver doesn't
> implement it :-\


My bad, will fix this.

Thanks


> Thanks,
>
> Alex
>
>> + *				is accepted by the device.
>> + * @set_vq_address:		Set the address of virtqueue
>> + *				@mdev: mediated device
>> + *				@idx: virtqueue index
>> + *				@desc_area: address of desc area
>> + *				@driver_area: address of driver area
>> + *				@device_area: address of device area
>> + *				Returns integer: success (0) or error (< 0)
>> + * @set_vq_num:			Set the size of virtqueue
>> + *				@mdev: mediated device
>> + *				@idx: virtqueue index
>> + *				@num: the size of virtqueue
>> + * @kick_vq:			Kick the virtqueue
>> + *				@mdev: mediated device
>> + *				@idx: virtqueue index
>> + * @set_vq_cb:			Set the interrupt callback function for
>> + *				a virtqueue
>> + *				@mdev: mediated device
>> + *				@idx: virtqueue index
>> + *				@cb: virtio-mdev interrupt callback structure
>> + * @set_vq_ready:		Set ready status for a virtqueue
>> + *				@mdev: mediated device
>> + *				@idx: virtqueue index
>> + *				@ready: ready (true) not ready(false)
>> + * @get_vq_ready:		Get ready status for a virtqueue
>> + *				@mdev: mediated device
>> + *				@idx: virtqueue index
>> + *				Returns boolean: ready (true) or not (false)
>> + * @set_vq_state:		Set the state for a virtqueue
>> + *				@mdev: mediated device
>> + *				@idx: virtqueue index
>> + *				@state: virtqueue state (last_avail_idx)
>> + *				Returns integer: success (0) or error (< 0)
>> + * @get_vq_state:		Get the state for a virtqueue
>> + *				@mdev: mediated device
>> + *				@idx: virtqueue index
>> + *				Returns virtqueue state (last_avail_idx)
>> + * @get_vq_align:		Get the virtqueue align requirement
>> + *				for the device
>> + *				@mdev: mediated device
>> + *				Returns virtqueue algin requirement
>> + * @get_features:		Get virtio features supported by the device
>> + *				@mdev: mediated device
>> + *				Returns the virtio features support by the
>> + *				device
>> + * @set_features:		Set virtio features supported by the driver
>> + *				@mdev: mediated device
>> + *				@features: feature support by the driver
>> + *				Returns integer: success (0) or error (< 0)
>> + * @set_config_cb:		Set the config interrupt callback
>> + *				@mdev: mediated device
>> + *				@cb: virtio-mdev interrupt callback structure
>> + * @get_vq_num_max:		Get the max size of virtqueue
>> + *				@mdev: mediated device
>> + *				Returns u16: max size of virtqueue
>> + * @get_device_id:		Get virtio device id
>> + *				@mdev: mediated device
>> + *				Returns u32: virtio device id
>> + * @get_vendor_id:		Get id for the vendor that provides this device
>> + *				@mdev: mediated device
>> + *				Returns u32: virtio vendor id
>> + * @get_status:			Get the device status
>> + *				@mdev: mediated device
>> + *				Returns u8: virtio device status
>> + * @set_status:			Set the device status
>> + *				@mdev: mediated device
>> + *				@status: virtio device status
>> + * @get_config:			Read from device specific configuration space
>> + *				@mdev: mediated device
>> + *				@offset: offset from the beginning of
>> + *				configuration space
>> + *				@buf: buffer used to read to
>> + *				@len: the length to read from
>> + *				configration space
>> + * @set_config:			Write to device specific configuration space
>> + *				@mdev: mediated device
>> + *				@offset: offset from the beginning of
>> + *				configuration space
>> + *				@buf: buffer used to write from
>> + *				@len: the length to write to
>> + *				configration space
>> + * @get_generation:		Get device config generaton (optional)
>> + *				@mdev: mediated device
>> + *				Returns u32: device generation
>> + */
>> +struct mdev_virtio_device_ops {
>> +	/* Mdev device ops */
>> +	u64 (*get_mdev_features)(struct mdev_device *mdev);
>> +	bool (*set_mdev_feature)(struct mdev_device *mdev);
>> +	/* Virtqueue ops */
>> +	int (*set_vq_address)(struct mdev_device *mdev,
>> +			      u16 idx, u64 desc_area, u64 driver_area,
>> +			      u64 device_area);
>> +	void (*set_vq_num)(struct mdev_device *mdev, u16 idx, u32 num);
>> +	void (*kick_vq)(struct mdev_device *mdev, u16 idx);
>> +	void (*set_vq_cb)(struct mdev_device *mdev, u16 idx,
>> +			  struct virtio_mdev_callback *cb);
>> +	void (*set_vq_ready)(struct mdev_device *mdev, u16 idx, bool ready);
>> +	bool (*get_vq_ready)(struct mdev_device *mdev, u16 idx);
>> +	int (*set_vq_state)(struct mdev_device *mdev, u16 idx, u64 state);
>> +	u64 (*get_vq_state)(struct mdev_device *mdev, u16 idx);
>> +
>> +	/* Virtio device ops */
>> +	u16 (*get_vq_align)(struct mdev_device *mdev);
>> +	u64 (*get_features)(struct mdev_device *mdev);
>> +	int (*set_features)(struct mdev_device *mdev, u64 features);
>> +	void (*set_config_cb)(struct mdev_device *mdev,
>> +			      struct virtio_mdev_callback *cb);
>> +	u16 (*get_vq_num_max)(struct mdev_device *mdev);
>> +	u32 (*get_device_id)(struct mdev_device *mdev);
>> +	u32 (*get_vendor_id)(struct mdev_device *mdev);
>> +	u8 (*get_status)(struct mdev_device *mdev);
>> +	void (*set_status)(struct mdev_device *mdev, u8 status);
>> +	void (*get_config)(struct mdev_device *mdev, unsigned int offset,
>> +			   void *buf, unsigned int len);
>> +	void (*set_config)(struct mdev_device *mdev, unsigned int offset,
>> +			   const void *buf, unsigned int len);
>> +	u32 (*get_generation)(struct mdev_device *mdev);
>> +};
>> +
>> +void mdev_set_virtio_ops(struct mdev_device *mdev,
>> +			 const struct mdev_virtio_device_ops *virtio_ops);
>> +
>> +#endif



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