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

From: Alex Williamson
Date: Wed Oct 23 2019 - 17:58:05 EST

On Wed, 23 Oct 2019 21:07:50 +0800
Jason Wang <jasowang@xxxxxxxxxx> wrote:

> This patch implements basic support for mdev driver that supports
> virtio transport for kernel virtio driver.
>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> 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@xxxxxxxxxx>
> + */
> +#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.

> + *
> + * @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


> + * @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