> -----Original Message-----
> From: Jason Wang <jasow...@redhat.com>
> Sent: Monday, September 23, 2019 8:03 AM
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> <pa...@mellanox.com>; Jason Wang <jasow...@redhat.com>
> Subject: [PATCH 4/6] virtio: introduce a mdev based transport
> 
> This patch introduces a new mdev transport for virtio. This is used to use 
> kernel
> virtio driver to drive the mediated device that is capable of populating
> virtqueue directly.
> 
> A new virtio-mdev driver will be registered to the mdev bus, when a new 
> virtio-
> mdev device is probed, it will register the device with mdev based config ops.
> This means it is a software transport between mdev driver and mdev device.
> The transport was implemented through device specific opswhich is a part of
> mdev_parent_ops now.
> 
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
>  MAINTAINERS                     |   1 +
>  drivers/vfio/mdev/Kconfig       |   7 +
>  drivers/vfio/mdev/Makefile      |   1 +
>  drivers/vfio/mdev/virtio_mdev.c | 416 ++++++++++++++++++++++++++++++++
>  4 files changed, 425 insertions(+)
>  create mode 100644 drivers/vfio/mdev/virtio_mdev.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 89832b316500..820ec250cc52 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -17202,6 +17202,7 @@ F:    include/linux/virtio*.h
>  F:   include/uapi/linux/virtio_*.h
>  F:   drivers/crypto/virtio/
>  F:   mm/balloon_compaction.c
> +F:   drivers/vfio/mdev/virtio_mdev.c
> 
>  VIRTIO BLOCK AND SCSI DRIVERS
>  M:   "Michael S. Tsirkin" <m...@redhat.com>
> diff --git a/drivers/vfio/mdev/Kconfig b/drivers/vfio/mdev/Kconfig index
> 5da27f2100f9..c488c31fc137 100644
> --- a/drivers/vfio/mdev/Kconfig
> +++ b/drivers/vfio/mdev/Kconfig
> @@ -16,3 +16,10 @@ config VFIO_MDEV_DEVICE
>       default n
>       help
>         VFIO based driver for Mediated devices.
> +
> +config VIRTIO_MDEV_DEVICE
> +     tristate "VIRTIO driver for Mediated devices"
> +     depends on VFIO_MDEV && VIRTIO
> +     default n
> +     help
> +       VIRTIO based driver for Mediated devices.
> diff --git a/drivers/vfio/mdev/Makefile b/drivers/vfio/mdev/Makefile index
> 101516fdf375..99d31e29c23e 100644
> --- a/drivers/vfio/mdev/Makefile
> +++ b/drivers/vfio/mdev/Makefile
> @@ -4,3 +4,4 @@ mdev-y := mdev_core.o mdev_sysfs.o mdev_driver.o
> 
>  obj-$(CONFIG_VFIO_MDEV) += mdev.o
>  obj-$(CONFIG_VFIO_MDEV_DEVICE) += vfio_mdev.o
> +obj-$(CONFIG_VIRTIO_MDEV_DEVICE) += virtio_mdev.o
> diff --git a/drivers/vfio/mdev/virtio_mdev.c b/drivers/vfio/mdev/virtio_mdev.c
> new file mode 100644 index 000000000000..919a082adc9c
> --- /dev/null
> +++ b/drivers/vfio/mdev/virtio_mdev.c
> @@ -0,0 +1,416 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * VIRTIO based driver for Mediated device
> + *
> + * Copyright (c) 2019, Red Hat. All rights reserved.
> + *     Author: Jason Wang <jasow...@redhat.com>
> + *
> + */
> +
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/uuid.h>
> +#include <linux/mdev.h>
> +#include <linux/virtio_mdev.h>
> +#include <linux/virtio.h>
> +#include <linux/virtio_config.h>
> +#include <linux/virtio_ring.h>
> +#include "mdev_private.h"
> +
> +#define DRIVER_VERSION  "0.1"
> +#define DRIVER_AUTHOR   "Red Hat Corporation"
> +#define DRIVER_DESC     "VIRTIO based driver for Mediated device"
> +
> +#define to_virtio_mdev_device(dev) \
> +     container_of(dev, struct virtio_mdev_device, vdev)
> +
> +struct virtio_mdev_device {
> +     struct virtio_device vdev;
> +     struct mdev_device *mdev;
> +     unsigned long version;
> +
> +     struct virtqueue **vqs;
Every lock must need a comment to describe what it locks.
I don't see this lock is used in this patch. Please introduce in the patch that 
uses it.
> +     spinlock_t lock;
> +};
> +
> +struct virtio_mdev_vq_info {
> +     /* the actual virtqueue */
> +     struct virtqueue *vq;
> +
> +     /* the list node for the virtqueues list */
> +     struct list_head node;
> +};
> +
> +static struct mdev_device *vm_get_mdev(struct virtio_device *vdev) {
> +     struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vdev);
> +     struct mdev_device *mdev = vm_dev->mdev;
> +
> +     return mdev;
> +}
> +
> +static const struct virtio_mdev_parent_ops *mdev_get_parent_ops(struct
> +mdev_device *mdev) {
> +     struct mdev_parent *parent = mdev->parent;
> +
> +     return parent->ops->device_ops;
> +}
> +
> +static void virtio_mdev_get(struct virtio_device *vdev, unsigned offset,
> +                         void *buf, unsigned len)
> +{
> +     struct mdev_device *mdev = vm_get_mdev(vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +
> +     ops->get_config(mdev, offset, buf, len); }
> +
> +static void virtio_mdev_set(struct virtio_device *vdev, unsigned offset,
> +                         const void *buf, unsigned len)
> +{
> +     struct mdev_device *mdev = vm_get_mdev(vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +
> +     ops->set_config(mdev, offset, buf, len); }
> +
> +static u32 virtio_mdev_generation(struct virtio_device *vdev) {
> +     struct mdev_device *mdev = vm_get_mdev(vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +
> +     return ops->get_generation(mdev);
> +}
> +
> +static u8 virtio_mdev_get_status(struct virtio_device *vdev) {
> +     struct mdev_device *mdev = vm_get_mdev(vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +
> +     return ops->get_status(mdev);
> +}
> +
> +static void virtio_mdev_set_status(struct virtio_device *vdev, u8
> +status) {
> +     struct mdev_device *mdev = vm_get_mdev(vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +
> +     return ops->set_status(mdev, status);
> +}
> +
> +static void virtio_mdev_reset(struct virtio_device *vdev) {
> +     struct mdev_device *mdev = vm_get_mdev(vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +
> +     return ops->set_status(mdev, 0);
> +}
> +
> +static bool virtio_mdev_notify(struct virtqueue *vq) {
> +     struct mdev_device *mdev = vm_get_mdev(vq->vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +
> +     ops->kick_vq(mdev, vq->index);
> +
> +     return true;
> +}
> +
> +static irqreturn_t virtio_mdev_config_cb(void *private) {
> +     struct virtio_mdev_device *vm_dev = private;
> +
> +     virtio_config_changed(&vm_dev->vdev);
> +
> +     return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t virtio_mdev_virtqueue_cb(void *private) {
> +     struct virtio_mdev_vq_info *info = private;
> +
> +     return vring_interrupt(0, info->vq);
> +}
> +
> +static struct virtqueue *
> +virtio_mdev_setup_vq(struct virtio_device *vdev, unsigned index,
> +                  void (*callback)(struct virtqueue *vq),
> +                  const char *name, bool ctx)
> +{
> +     struct mdev_device *mdev = vm_get_mdev(vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +     struct virtio_mdev_vq_info *info;
> +     struct virtio_mdev_callback cb;
> +     struct virtqueue *vq;
> +     u32 align, num;
> +     u64 desc_addr, driver_addr, device_addr;
> +     int err;
> +
> +     if (!name)
> +             return NULL;
> +
> +     /* Queue shouldn't already be set up. */
> +     if (ops->get_vq_ready(mdev, index)) {
> +             err = -ENOENT;
> +             goto error_available;
> +     }
> +
No need for a goto, to single return done later.
Just do 
        if (ops->get_vq_ready(mdev, index))
                return -ENOENT;

> +     /* Allocate and fill out our active queue description */
> +     info = kmalloc(sizeof(*info), GFP_KERNEL);
> +     if (!info) {
> +             err = -ENOMEM;
> +             goto error_kmalloc;
> +     }
> +
Similar to above one.

> +     num = ops->get_queue_max(mdev);
> +     if (num == 0) {
> +             err = -ENOENT;
> +             goto error_new_virtqueue;
> +     }
> +
> +     /* Create the vring */
> +     align = ops->get_vq_align(mdev);
> +     vq = vring_create_virtqueue(index, num, align, vdev,
> +                                 true, true, ctx,
> +                                 virtio_mdev_notify, callback, name);
> +     if (!vq) {
> +             err = -ENOMEM;
> +             goto error_new_virtqueue;
> +     }
> +
> +     /* Setup virtqueue callback */
> +     cb.callback = virtio_mdev_virtqueue_cb;
> +     cb.private = info;
> +     ops->set_vq_cb(mdev, index, &cb);
> +     ops->set_vq_num(mdev, index, virtqueue_get_vring_size(vq));
> +
> +     desc_addr = virtqueue_get_desc_addr(vq);
> +     driver_addr = virtqueue_get_avail_addr(vq);
> +     device_addr = virtqueue_get_used_addr(vq);
> +
> +     if (ops->set_vq_address(mdev, index,
> +                             desc_addr, driver_addr,
> +                             device_addr)) {
> +             err = -EINVAL;
> +             goto err_vq;
> +     }
> +
> +     ops->set_vq_ready(mdev, index, 1);
> +
> +     vq->priv = info;
> +     info->vq = vq;
> +
> +     return vq;
> +
> +err_vq:
> +     vring_del_virtqueue(vq);
> +error_new_virtqueue:
> +     ops->set_vq_ready(mdev, index, 0);
> +     WARN_ON(ops->get_vq_ready(mdev, index));
> +     kfree(info);
> +error_kmalloc:
> +error_available:
> +     return ERR_PTR(err);
> +
> +}
> +
> +static void virtio_mdev_del_vq(struct virtqueue *vq) {
> +     struct mdev_device *mdev = vm_get_mdev(vq->vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +     struct virtio_mdev_vq_info *info = vq->priv;
> +     unsigned int index = vq->index;
> +
> +     /* Select and deactivate the queue */
> +     ops->set_vq_ready(mdev, index, 0);
> +     WARN_ON(ops->get_vq_ready(mdev, index));
> +
> +     vring_del_virtqueue(vq);
> +
> +     kfree(info);
> +}
> +
> +static void virtio_mdev_del_vqs(struct virtio_device *vdev) {
> +     struct virtqueue *vq, *n;
> +
> +     list_for_each_entry_safe(vq, n, &vdev->vqs, list)
> +             virtio_mdev_del_vq(vq);
> +}
> +
> +static int virtio_mdev_find_vqs(struct virtio_device *vdev, unsigned nvqs,
> +                             struct virtqueue *vqs[],
> +                             vq_callback_t *callbacks[],
> +                             const char * const names[],
> +                             const bool *ctx,
> +                             struct irq_affinity *desc)
> +{
> +     struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vdev);
> +     struct mdev_device *mdev = vm_get_mdev(vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +     struct virtio_mdev_callback cb;
> +     int i, err, queue_idx = 0;
> +
> +     vm_dev->vqs = kmalloc_array(queue_idx, sizeof(*vm_dev->vqs),
> +                                 GFP_KERNEL);
> +     if (!vm_dev->vqs)
> +             return -ENOMEM;
> +
> +     for (i = 0; i < nvqs; ++i) {
> +             if (!names[i]) {
> +                     vqs[i] = NULL;
> +                     continue;
> +             }
> +
> +             vqs[i] = virtio_mdev_setup_vq(vdev, queue_idx++,
> +                                           callbacks[i], names[i], ctx ?
> +                                           ctx[i] : false);
> +             if (IS_ERR(vqs[i])) {
> +                     err = PTR_ERR(vqs[i]);
> +                     goto err_setup_vq;
> +             }
> +     }
> +
> +     cb.callback = virtio_mdev_config_cb;
> +     cb.private = vm_dev;
> +     ops->set_config_cb(mdev, &cb);
> +
> +     return 0;
> +
> +err_setup_vq:
> +     kfree(vm_dev->vqs);
> +     virtio_mdev_del_vqs(vdev);
> +     return err;
> +}
> +
> +static u64 virtio_mdev_get_features(struct virtio_device *vdev) {
> +     struct mdev_device *mdev = vm_get_mdev(vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +
> +     return ops->get_features(mdev);
> +}
> +
> +static int virtio_mdev_finalize_features(struct virtio_device *vdev) {
> +     struct mdev_device *mdev = vm_get_mdev(vdev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +
> +     /* Give virtio_ring a chance to accept features. */
> +     vring_transport_features(vdev);
> +
> +     return ops->set_features(mdev, vdev->features); }
> +
> +static const char *virtio_mdev_bus_name(struct virtio_device *vdev) {
> +     struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vdev);
> +     struct mdev_device *mdev = vm_dev->mdev;
> +
> +     return dev_name(&mdev->dev);
> +}
> +
> +static const struct virtio_config_ops virtio_mdev_config_ops = {
> +     .get            = virtio_mdev_get,
> +     .set            = virtio_mdev_set,
> +     .generation     = virtio_mdev_generation,
> +     .get_status     = virtio_mdev_get_status,
> +     .set_status     = virtio_mdev_set_status,
> +     .reset          = virtio_mdev_reset,
> +     .find_vqs       = virtio_mdev_find_vqs,
> +     .del_vqs        = virtio_mdev_del_vqs,
> +     .get_features   = virtio_mdev_get_features,
> +     .finalize_features = virtio_mdev_finalize_features,
> +     .bus_name       = virtio_mdev_bus_name,
> +};
> +
> +static void virtio_mdev_release_dev(struct device *_d) {
> +     struct virtio_device *vdev =
> +            container_of(_d, struct virtio_device, dev);
> +     struct virtio_mdev_device *vm_dev =
> +            container_of(vdev, struct virtio_mdev_device, vdev);
> +
> +     devm_kfree(_d, vm_dev);
> +}
> +
> +static int virtio_mdev_probe(struct device *dev) {
> +     struct mdev_device *mdev = to_mdev_device(dev);
> +     const struct virtio_mdev_parent_ops *ops =
> mdev_get_parent_ops(mdev);
> +     struct virtio_mdev_device *vm_dev;
> +     int rc;
> +
> +     vm_dev = devm_kzalloc(dev, sizeof(*vm_dev), GFP_KERNEL);
> +     if (!vm_dev)
> +             return -ENOMEM;
> +
> +     vm_dev->vdev.dev.parent = dev;
> +     vm_dev->vdev.dev.release = virtio_mdev_release_dev;
> +     vm_dev->vdev.config = &virtio_mdev_config_ops;
> +     vm_dev->mdev = mdev;
> +     vm_dev->vqs = NULL;
> +     spin_lock_init(&vm_dev->lock);
> +
> +     vm_dev->version = ops->get_version(mdev);
> +     if (vm_dev->version != 1) {
> +             dev_err(dev, "Version %ld not supported!\n",
> +                     vm_dev->version);
> +             return -ENXIO;
> +     }
> +
> +     vm_dev->vdev.id.device = ops->get_device_id(mdev);
> +     if (vm_dev->vdev.id.device == 0)
> +             return -ENODEV;
> +
> +     vm_dev->vdev.id.vendor = ops->get_vendor_id(mdev);
> +     rc = register_virtio_device(&vm_dev->vdev);
> +     if (rc)
> +             put_device(dev);
> +
> +     dev_set_drvdata(dev, vm_dev);
No need to set drvdata when there is error returned from 
register_virtio_device().

> +
> +     return rc;
> +
Extra line not needed.
> +}
> +
> +static void virtio_mdev_remove(struct device *dev) {
> +     struct virtio_mdev_device *vm_dev = dev_get_drvdata(dev);
> +
> +     unregister_virtio_device(&vm_dev->vdev);
> +}
> +
> +static struct mdev_class_id id_table[] = {
> +     { MDEV_ID_VIRTIO },
> +     { 0 },
> +};
> +
> +static struct mdev_driver virtio_mdev_driver = {
> +     .name   = "virtio_mdev",
> +     .probe  = virtio_mdev_probe,
> +     .remove = virtio_mdev_remove,
No need for tab, just do single white space.

> +     .id_table = id_table,
> +};
> +
> +static int __init virtio_mdev_init(void) {
> +     return mdev_register_driver(&virtio_mdev_driver, THIS_MODULE); }
> +
> +static void __exit virtio_mdev_exit(void) {
> +     mdev_unregister_driver(&virtio_mdev_driver);
> +}
> +
> +module_init(virtio_mdev_init)
> +module_exit(virtio_mdev_exit)
> +
> +MODULE_VERSION(DRIVER_VERSION);
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR(DRIVER_AUTHOR);
> +MODULE_DESCRIPTION(DRIVER_DESC);
> --
> 2.19.1

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