Re: [PATCH V5 4/6] mdev: introduce virtio device and its device ops

[Jason Wang <jasowang@redhat.com>]

On 2019/10/24 上午5:57, Alex Williamson wrote:
> On Wed, 23 Oct 2019 21:07:50 +0800
> Jason Wang <jasowang@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@redhat.com>
>> ---
>>   drivers/vfio/mdev/mdev_core.c    |  20 ++++
>>   drivers/vfio/mdev/mdev_private.h |   2 +
>>   include/linux/mdev.h             |   6 ++
>>   include/linux/virtio_mdev_ops.h  | 159 +++++++++++++++++++++++++++++++
>>   4 files changed, 187 insertions(+)
>>   create mode 100644 include/linux/virtio_mdev_ops.h
>>
>> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
>> index 555bd61d8c38..9b00c3513120 100644
>> --- a/drivers/vfio/mdev/mdev_core.c
>> +++ b/drivers/vfio/mdev/mdev_core.c
>> @@ -76,6 +76,26 @@ const struct vfio_mdev_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.
>> + */
>> +void mdev_set_virtio_ops(struct mdev_device *mdev,
>> +			 const struct virtio_mdev_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 virtio_mdev_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 0770410ded2a..7b47890c34e7 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/vfio_mdev_ops.h>
>> +#include <linux/virtio_mdev_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 vfio_mdev_device_ops *vfio_ops;
>> +		const struct virtio_mdev_device_ops *virtio_ops;
>>   	};
>>   };
>>   
>> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
>> index 4625f1a11014..9b69b0bbebfd 100644
>> --- a/include/linux/mdev.h
>> +++ b/include/linux/mdev.h
>> @@ -17,6 +17,7 @@
>>   
>>   struct mdev_device;
>>   struct vfio_mdev_device_ops;
>> +struct virtio_mdev_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 vfio_mdev_device_ops *vfio_ops);
>>   const struct vfio_mdev_device_ops *mdev_get_vfio_ops(struct mdev_device *mdev);
>> +void mdev_set_virtio_ops(struct mdev_device *mdev,
>> +			 const struct virtio_mdev_device_ops *virtio_ops);
>> +const struct virtio_mdev_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/virtio_mdev_ops.h b/include/linux/virtio_mdev_ops.h
>> new file mode 100644
>> index 000000000000..d417b41f2845
>> --- /dev/null
>> +++ b/include/linux/virtio_mdev_ops.h
>> @@ -0,0 +1,159 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Virtio mediated device driver
>> + *
>> + * Copyright 2019, Red Hat Corp.
>> + *     Author: Jason Wang <jasowang@redhat.com>
>> + */
>> +#ifndef _LINUX_VIRTIO_MDEV_H
>> +#define _LINUX_VIRTIO_MDEV_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 vfio_mdev_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.
> If the version of the callbacks is returned by a callback within the
> structure defined by the version... isn't that a bit circular?  This
> seems redundant to me versus the class id.  The fact that the parent
> driver defines the device as MDEV_CLASS_ID_VIRTIO should tell us this
> already.  If it was incremented, we'd need an MDEV_CLASS_ID_VIRTIOv2,
> which the virtio-mdev bus driver could add to its id table and handle
> differently.


My understanding is versions are only allowed to increase monotonically, 
this seems less flexible than features. E.g we have features A, B, C, 
mdev device can choose to support only a subset. E.g when mdev device 
can support dirty page logging, it can add a new feature bit for driver 
to know that it support new device ops. MDEV_CLASS_ID_VIRTIOv2 may only 
be useful when we will invent a complete new API.


>
>> + *
>> + * @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
>> + * @get_features:		Set virtio features supported by the driver
>         ^ s/g/s/
>
> Thanks,
> Alex


Will fix.

Thanks


>
>> + *				@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_mdev_features:		Get a set of bits that demonstrate
>> + *				thecapability of the mdev device. New
>> + *				features bits must be added when
>> + *				introducing new device ops.
>> + *				@mdev: mediated device
>> + *				Returns the mdev features (API) support by
>> + *				the device.
>> + * @get_generation:		Get device config generaton (optionally)
>> + *				@mdev: mediated device
>> + *				Returns u32: device generation
>> + */
>> +struct virtio_mdev_device_ops {
>> +	/* 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);
>> +
>> +	/* Mdev device ops */
>> +	u64 (*get_mdev_features)(struct mdev_device *mdev);
>> +};
>> +
>> +void mdev_set_virtio_ops(struct mdev_device *mdev,
>> +			 const struct virtio_mdev_device_ops *virtio_ops);
>> +
>> +#endif