// SPDX-License-Identifier: GPL-2.0-only
/*
 * VIRTIO based driver for vDPA device
 *
 * Copyright (c) 2020, Red Hat. All rights reserved.
 *     Author: Jason Wang <jasowang@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/virtio.h>
#include <linux/vdpa.h>
#include <linux/virtio_config.h>
#include <linux/virtio_ring.h>

#define MOD_VERSION  "0.1"
#define MOD_AUTHOR   "Jason Wang <jasowang@redhat.com>"
#define MOD_DESC     "vDPA bus driver for virtio devices"
#define MOD_LICENSE  "GPL v2"

struct virtio_vdpa_device {
        struct virtio_device vdev;
        struct vdpa_device *vdpa;
        u64 features;

        /* The lock to protect virtqueue list */
        spinlock_t lock;
        /* List of virtio_vdpa_vq_info */
        struct list_head virtqueues;
};

struct virtio_vdpa_vq_info {
        /* the actual virtqueue */
        struct virtqueue *vq;

        /* the list node for the virtqueues list */
        struct list_head node;
};

static inline struct virtio_vdpa_device *
to_virtio_vdpa_device(struct virtio_device *dev)
{
        return container_of(dev, struct virtio_vdpa_device, vdev);
}

static struct vdpa_device *vd_get_vdpa(struct virtio_device *vdev)
{
        return to_virtio_vdpa_device(vdev)->vdpa;
}

static void virtio_vdpa_get(struct virtio_device *vdev, unsigned offset,
                            void *buf, unsigned len)
{
        struct vdpa_device *vdpa = vd_get_vdpa(vdev);

        vdpa_get_config(vdpa, offset, buf, len);
}

static void virtio_vdpa_set(struct virtio_device *vdev, unsigned offset,
                            const void *buf, unsigned len)
{
        struct vdpa_device *vdpa = vd_get_vdpa(vdev);
        const struct vdpa_config_ops *ops = vdpa->config;

        ops->set_config(vdpa, offset, buf, len);
}

static u32 virtio_vdpa_generation(struct virtio_device *vdev)
{
        struct vdpa_device *vdpa = vd_get_vdpa(vdev);
        const struct vdpa_config_ops *ops = vdpa->config;

        if (ops->get_generation)
                return ops->get_generation(vdpa);

        return 0;
}

static u8 virtio_vdpa_get_status(struct virtio_device *vdev)
{
        struct vdpa_device *vdpa = vd_get_vdpa(vdev);
        const struct vdpa_config_ops *ops = vdpa->config;

        return ops->get_status(vdpa);
}

static void virtio_vdpa_set_status(struct virtio_device *vdev, u8 status)
{
        struct vdpa_device *vdpa = vd_get_vdpa(vdev);
        const struct vdpa_config_ops *ops = vdpa->config;

        return ops->set_status(vdpa, status);
}

static void virtio_vdpa_reset(struct virtio_device *vdev)
{
        struct vdpa_device *vdpa = vd_get_vdpa(vdev);

        vdpa_reset(vdpa);
}

static bool virtio_vdpa_notify(struct virtqueue *vq)
{
        struct vdpa_device *vdpa = vd_get_vdpa(vq->vdev);
        const struct vdpa_config_ops *ops = vdpa->config;

        ops->kick_vq(vdpa, vq->index);

        return true;
}

static irqreturn_t virtio_vdpa_config_cb(void *private)
{
        struct virtio_vdpa_device *vd_dev = private;

        virtio_config_changed(&vd_dev->vdev);

        return IRQ_HANDLED;
}

static irqreturn_t virtio_vdpa_virtqueue_cb(void *private)
{
        struct virtio_vdpa_vq_info *info = private;

        return vring_interrupt(0, info->vq);
}

static struct virtqueue *
virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index,
                     void (*callback)(struct virtqueue *vq),
                     const char *name, bool ctx)
{
        struct virtio_vdpa_device *vd_dev = to_virtio_vdpa_device(vdev);
        struct vdpa_device *vdpa = vd_get_vdpa(vdev);
        const struct vdpa_config_ops *ops = vdpa->config;
        struct virtio_vdpa_vq_info *info;
        struct vdpa_callback cb;
        struct virtqueue *vq;
        u64 desc_addr, driver_addr, device_addr;
        unsigned long flags;
        u32 align, num;
        int err;

        if (!name)
                return NULL;

        /* Queue shouldn't already be set up. */
        if (ops->get_vq_ready(vdpa, index))
                return ERR_PTR(-ENOENT);

        /* Allocate and fill out our active queue description */
        info = kmalloc(sizeof(*info), GFP_KERNEL);
        if (!info)
                return ERR_PTR(-ENOMEM);

        num = ops->get_vq_num_max(vdpa);
        if (num == 0) {
                err = -ENOENT;
                goto error_new_virtqueue;
        }

        /* Create the vring */
        align = ops->get_vq_align(vdpa);
        vq = vring_create_virtqueue(index, num, align, vdev,
                                    true, true, ctx,
                                    virtio_vdpa_notify, callback, name);
        if (!vq) {
                err = -ENOMEM;
                goto error_new_virtqueue;
        }

        /* Setup virtqueue callback */
        cb.callback = virtio_vdpa_virtqueue_cb;
        cb.private = info;
        ops->set_vq_cb(vdpa, index, &cb);
        ops->set_vq_num(vdpa, 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(vdpa, index,
                                desc_addr, driver_addr,
                                device_addr)) {
                err = -EINVAL;
                goto err_vq;
        }

        ops->set_vq_ready(vdpa, index, 1);

        vq->priv = info;
        info->vq = vq;

        spin_lock_irqsave(&vd_dev->lock, flags);
        list_add(&info->node, &vd_dev->virtqueues);
        spin_unlock_irqrestore(&vd_dev->lock, flags);

        return vq;

err_vq:
        vring_del_virtqueue(vq);
error_new_virtqueue:
        ops->set_vq_ready(vdpa, index, 0);
        /* VDPA driver should make sure vq is stopeed here */
        WARN_ON(ops->get_vq_ready(vdpa, index));
        kfree(info);
        return ERR_PTR(err);
}

static void virtio_vdpa_del_vq(struct virtqueue *vq)
{
        struct virtio_vdpa_device *vd_dev = to_virtio_vdpa_device(vq->vdev);
        struct vdpa_device *vdpa = vd_dev->vdpa;
        const struct vdpa_config_ops *ops = vdpa->config;
        struct virtio_vdpa_vq_info *info = vq->priv;
        unsigned int index = vq->index;
        unsigned long flags;

        spin_lock_irqsave(&vd_dev->lock, flags);
        list_del(&info->node);
        spin_unlock_irqrestore(&vd_dev->lock, flags);

        /* Select and deactivate the queue */
        ops->set_vq_ready(vdpa, index, 0);
        WARN_ON(ops->get_vq_ready(vdpa, index));

        vring_del_virtqueue(vq);

        kfree(info);
}

static void virtio_vdpa_del_vqs(struct virtio_device *vdev)
{
        struct virtqueue *vq, *n;

        list_for_each_entry_safe(vq, n, &vdev->vqs, list)
                virtio_vdpa_del_vq(vq);
}

static int virtio_vdpa_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_vdpa_device *vd_dev = to_virtio_vdpa_device(vdev);
        struct vdpa_device *vdpa = vd_get_vdpa(vdev);
        const struct vdpa_config_ops *ops = vdpa->config;
        struct vdpa_callback cb;
        int i, err, queue_idx = 0;

        for (i = 0; i < nvqs; ++i) {
                if (!names[i]) {
                        vqs[i] = NULL;
                        continue;
                }

                vqs[i] = virtio_vdpa_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_vdpa_config_cb;
        cb.private = vd_dev;
        ops->set_config_cb(vdpa, &cb);

        return 0;

err_setup_vq:
        virtio_vdpa_del_vqs(vdev);
        return err;
}

static u64 virtio_vdpa_get_features(struct virtio_device *vdev)
{
        struct vdpa_device *vdpa = vd_get_vdpa(vdev);
        const struct vdpa_config_ops *ops = vdpa->config;

        return ops->get_features(vdpa);
}

static int virtio_vdpa_finalize_features(struct virtio_device *vdev)
{
        struct vdpa_device *vdpa = vd_get_vdpa(vdev);

        /* Give virtio_ring a chance to accept features. */
        vring_transport_features(vdev);

        return vdpa_set_features(vdpa, vdev->features);
}

static const char *virtio_vdpa_bus_name(struct virtio_device *vdev)
{
        struct virtio_vdpa_device *vd_dev = to_virtio_vdpa_device(vdev);
        struct vdpa_device *vdpa = vd_dev->vdpa;

        return dev_name(&vdpa->dev);
}

static const struct virtio_config_ops virtio_vdpa_config_ops = {
        .get            = virtio_vdpa_get,
        .set            = virtio_vdpa_set,
        .generation     = virtio_vdpa_generation,
        .get_status     = virtio_vdpa_get_status,
        .set_status     = virtio_vdpa_set_status,
        .reset          = virtio_vdpa_reset,
        .find_vqs       = virtio_vdpa_find_vqs,
        .del_vqs        = virtio_vdpa_del_vqs,
        .get_features   = virtio_vdpa_get_features,
        .finalize_features = virtio_vdpa_finalize_features,
        .bus_name       = virtio_vdpa_bus_name,
};

static void virtio_vdpa_release_dev(struct device *_d)
{
        struct virtio_device *vdev =
               container_of(_d, struct virtio_device, dev);
        struct virtio_vdpa_device *vd_dev =
               container_of(vdev, struct virtio_vdpa_device, vdev);

        kfree(vd_dev);
}

static int virtio_vdpa_probe(struct vdpa_device *vdpa)
{
        const struct vdpa_config_ops *ops = vdpa->config;
        struct virtio_vdpa_device *vd_dev, *reg_dev = NULL;
        int ret = -EINVAL;

        vd_dev = kzalloc(sizeof(*vd_dev), GFP_KERNEL);
        if (!vd_dev)
                return -ENOMEM;

        vd_dev->vdev.dev.parent = vdpa_get_dma_dev(vdpa);
        vd_dev->vdev.dev.release = virtio_vdpa_release_dev;
        vd_dev->vdev.config = &virtio_vdpa_config_ops;
        vd_dev->vdpa = vdpa;
        INIT_LIST_HEAD(&vd_dev->virtqueues);
        spin_lock_init(&vd_dev->lock);

        vd_dev->vdev.id.device = ops->get_device_id(vdpa);
        if (vd_dev->vdev.id.device == 0)
                goto err;

        vd_dev->vdev.id.vendor = ops->get_vendor_id(vdpa);
        ret = register_virtio_device(&vd_dev->vdev);
        reg_dev = vd_dev;
        if (ret)
                goto err;

        vdpa_set_drvdata(vdpa, vd_dev);

        return 0;

err:
        if (reg_dev)
                put_device(&vd_dev->vdev.dev);
        else
                kfree(vd_dev);
        return ret;
}

static void virtio_vdpa_remove(struct vdpa_device *vdpa)
{
        struct virtio_vdpa_device *vd_dev = vdpa_get_drvdata(vdpa);

        unregister_virtio_device(&vd_dev->vdev);
}

static struct vdpa_driver virtio_vdpa_driver = {
        .driver = {
                .name   = "virtio_vdpa",
        },
        .probe  = virtio_vdpa_probe,
        .remove = virtio_vdpa_remove,
};

module_vdpa_driver(virtio_vdpa_driver);

MODULE_VERSION(MOD_VERSION);
MODULE_LICENSE(MOD_LICENSE);
MODULE_AUTHOR(MOD_AUTHOR);
MODULE_DESCRIPTION(MOD_DESC);