// SPDX-License-Identifier: GPL-2.0-only
/*
 * VDPA networking device simulator.
 *
 * Copyright (c) 2020, Red Hat Inc. 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/fs.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/uuid.h>
#include <linux/iommu.h>
#include <linux/dma-mapping.h>
#include <linux/sysfs.h>
#include <linux/file.h>
#include <linux/etherdevice.h>
#include <linux/vringh.h>
#include <linux/vdpa.h>
#include <linux/virtio_byteorder.h>
#include <linux/vhost_iotlb.h>
#include <uapi/linux/virtio_config.h>
#include <uapi/linux/virtio_net.h>

#define DRV_VERSION  "0.1"
#define DRV_AUTHOR   "Jason Wang <jasowang@redhat.com>"
#define DRV_DESC     "vDPA Device Simulator"
#define DRV_LICENSE  "GPL v2"

static int batch_mapping = 1;
module_param(batch_mapping, int, 0444);
MODULE_PARM_DESC(batch_mapping, "Batched mapping 1 -Enable; 0 - Disable");

struct vdpasim_virtqueue {
        struct vringh vring;
        struct vringh_kiov iov;
        unsigned short head;
        bool ready;
        u64 desc_addr;
        u64 device_addr;
        u64 driver_addr;
        u32 num;
        void *private;
        irqreturn_t (*cb)(void *data);
};

#define VDPASIM_QUEUE_ALIGN PAGE_SIZE
#define VDPASIM_QUEUE_MAX 256
#define VDPASIM_DEVICE_ID 0x1
#define VDPASIM_VENDOR_ID 0
#define VDPASIM_VQ_NUM 0x2
#define VDPASIM_NAME "vdpasim-netdev"

static u64 vdpasim_features = (1ULL << VIRTIO_F_ANY_LAYOUT) |
                              (1ULL << VIRTIO_F_VERSION_1)  |
                              (1ULL << VIRTIO_F_ACCESS_PLATFORM);

/* State of each vdpasim device */
struct vdpasim {
        struct vdpa_device vdpa;
        struct vdpasim_virtqueue vqs[VDPASIM_VQ_NUM];
        struct work_struct work;
        /* spinlock to synchronize virtqueue state */
        spinlock_t lock;
        struct virtio_net_config config;
        struct vhost_iotlb *iommu;
        void *buffer;
        u32 status;
        u32 generation;
        u64 features;
        /* spinlock to synchronize iommu table */
        spinlock_t iommu_lock;
};

/* TODO: cross-endian support */
static inline bool vdpasim_is_little_endian(struct vdpasim *vdpasim)
{
        return virtio_legacy_is_little_endian() ||
                (vdpasim->features & (1ULL << VIRTIO_F_VERSION_1));
}

static inline u16 vdpasim16_to_cpu(struct vdpasim *vdpasim, __virtio16 val)
{
        return __virtio16_to_cpu(vdpasim_is_little_endian(vdpasim), val);
}

static inline __virtio16 cpu_to_vdpasim16(struct vdpasim *vdpasim, u16 val)
{
        return __cpu_to_virtio16(vdpasim_is_little_endian(vdpasim), val);
}

static struct vdpasim *vdpasim_dev;

static struct vdpasim *vdpa_to_sim(struct vdpa_device *vdpa)
{
        return container_of(vdpa, struct vdpasim, vdpa);
}

static struct vdpasim *dev_to_sim(struct device *dev)
{
        struct vdpa_device *vdpa = dev_to_vdpa(dev);

        return vdpa_to_sim(vdpa);
}

static void vdpasim_queue_ready(struct vdpasim *vdpasim, unsigned int idx)
{
        struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];

        vringh_init_iotlb(&vq->vring, vdpasim_features,
                          VDPASIM_QUEUE_MAX, false,
                          (struct vring_desc *)(uintptr_t)vq->desc_addr,
                          (struct vring_avail *)
                          (uintptr_t)vq->driver_addr,
                          (struct vring_used *)
                          (uintptr_t)vq->device_addr);
}

static void vdpasim_vq_reset(struct vdpasim_virtqueue *vq)
{
        vq->ready = false;
        vq->desc_addr = 0;
        vq->driver_addr = 0;
        vq->device_addr = 0;
        vq->cb = NULL;
        vq->private = NULL;
        vringh_init_iotlb(&vq->vring, vdpasim_features, VDPASIM_QUEUE_MAX,
                          false, NULL, NULL, NULL);
}

static void vdpasim_reset(struct vdpasim *vdpasim)
{
        int i;

        for (i = 0; i < VDPASIM_VQ_NUM; i++)
                vdpasim_vq_reset(&vdpasim->vqs[i]);

        spin_lock(&vdpasim->iommu_lock);
        vhost_iotlb_reset(vdpasim->iommu);
        spin_unlock(&vdpasim->iommu_lock);

        vdpasim->features = 0;
        vdpasim->status = 0;
        ++vdpasim->generation;
}

static void vdpasim_work(struct work_struct *work)
{
        struct vdpasim *vdpasim = container_of(work, struct
                                                 vdpasim, work);
        struct vdpasim_virtqueue *txq = &vdpasim->vqs[1];
        struct vdpasim_virtqueue *rxq = &vdpasim->vqs[0];
        ssize_t read, write;
        size_t total_write;
        int pkts = 0;
        int err;

        spin_lock(&vdpasim->lock);

        if (!(vdpasim->status & VIRTIO_CONFIG_S_DRIVER_OK))
                goto out;

        if (!txq->ready || !rxq->ready)
                goto out;

        while (true) {
                total_write = 0;
                err = vringh_getdesc_iotlb(&txq->vring, &txq->iov, NULL,
                                           &txq->head, GFP_ATOMIC);
                if (err <= 0)
                        break;

                err = vringh_getdesc_iotlb(&rxq->vring, NULL, &rxq->iov,
                                           &rxq->head, GFP_ATOMIC);
                if (err <= 0) {
                        vringh_complete_iotlb(&txq->vring, txq->head, 0);
                        break;
                }

                while (true) {
                        read = vringh_iov_pull_iotlb(&txq->vring, &txq->iov,
                                                     vdpasim->buffer,
                                                     PAGE_SIZE);
                        if (read <= 0)
                                break;

                        write = vringh_iov_push_iotlb(&rxq->vring, &rxq->iov,
                                                      vdpasim->buffer, read);
                        if (write <= 0)
                                break;

                        total_write += write;
                }

                /* Make sure data is wrote before advancing index */
                smp_wmb();

                vringh_complete_iotlb(&txq->vring, txq->head, 0);
                vringh_complete_iotlb(&rxq->vring, rxq->head, total_write);

                /* Make sure used is visible before rasing the interrupt. */
                smp_wmb();

                local_bh_disable();
                if (txq->cb)
                        txq->cb(txq->private);
                if (rxq->cb)
                        rxq->cb(rxq->private);
                local_bh_enable();

                if (++pkts > 4) {
                        schedule_work(&vdpasim->work);
                        goto out;
                }
        }

out:
        spin_unlock(&vdpasim->lock);
}

static int dir_to_perm(enum dma_data_direction dir)
{
        int perm = -EFAULT;

        switch (dir) {
        case DMA_FROM_DEVICE:
                perm = VHOST_MAP_WO;
                break;
        case DMA_TO_DEVICE:
                perm = VHOST_MAP_RO;
                break;
        case DMA_BIDIRECTIONAL:
                perm = VHOST_MAP_RW;
                break;
        default:
                break;
        }

        return perm;
}

static dma_addr_t vdpasim_map_page(struct device *dev, struct page *page,
                                   unsigned long offset, size_t size,
                                   enum dma_data_direction dir,
                                   unsigned long attrs)
{
        struct vdpasim *vdpasim = dev_to_sim(dev);
        struct vhost_iotlb *iommu = vdpasim->iommu;
        u64 pa = (page_to_pfn(page) << PAGE_SHIFT) + offset;
        int ret, perm = dir_to_perm(dir);

        if (perm < 0)
                return DMA_MAPPING_ERROR;

        /* For simplicity, use identical mapping to avoid e.g iova
         * allocator.
         */
        spin_lock(&vdpasim->iommu_lock);
        ret = vhost_iotlb_add_range(iommu, pa, pa + size - 1,
                                    pa, dir_to_perm(dir));
        spin_unlock(&vdpasim->iommu_lock);
        if (ret)
                return DMA_MAPPING_ERROR;

        return (dma_addr_t)(pa);
}

static void vdpasim_unmap_page(struct device *dev, dma_addr_t dma_addr,
                               size_t size, enum dma_data_direction dir,
                               unsigned long attrs)
{
        struct vdpasim *vdpasim = dev_to_sim(dev);
        struct vhost_iotlb *iommu = vdpasim->iommu;

        spin_lock(&vdpasim->iommu_lock);
        vhost_iotlb_del_range(iommu, (u64)dma_addr,
                              (u64)dma_addr + size - 1);
        spin_unlock(&vdpasim->iommu_lock);
}

static void *vdpasim_alloc_coherent(struct device *dev, size_t size,
                                    dma_addr_t *dma_addr, gfp_t flag,
                                    unsigned long attrs)
{
        struct vdpasim *vdpasim = dev_to_sim(dev);
        struct vhost_iotlb *iommu = vdpasim->iommu;
        void *addr = kmalloc(size, flag);
        int ret;

        spin_lock(&vdpasim->iommu_lock);
        if (!addr) {
                *dma_addr = DMA_MAPPING_ERROR;
        } else {
                u64 pa = virt_to_phys(addr);

                ret = vhost_iotlb_add_range(iommu, (u64)pa,
                                            (u64)pa + size - 1,
                                            pa, VHOST_MAP_RW);
                if (ret) {
                        *dma_addr = DMA_MAPPING_ERROR;
                        kfree(addr);
                        addr = NULL;
                } else
                        *dma_addr = (dma_addr_t)pa;
        }
        spin_unlock(&vdpasim->iommu_lock);

        return addr;
}

static void vdpasim_free_coherent(struct device *dev, size_t size,
                                  void *vaddr, dma_addr_t dma_addr,
                                  unsigned long attrs)
{
        struct vdpasim *vdpasim = dev_to_sim(dev);
        struct vhost_iotlb *iommu = vdpasim->iommu;

        spin_lock(&vdpasim->iommu_lock);
        vhost_iotlb_del_range(iommu, (u64)dma_addr,
                              (u64)dma_addr + size - 1);
        spin_unlock(&vdpasim->iommu_lock);

        kfree(phys_to_virt((uintptr_t)dma_addr));
}

static const struct dma_map_ops vdpasim_dma_ops = {
        .map_page = vdpasim_map_page,
        .unmap_page = vdpasim_unmap_page,
        .alloc = vdpasim_alloc_coherent,
        .free = vdpasim_free_coherent,
};

static const struct vdpa_config_ops vdpasim_net_config_ops;
static const struct vdpa_config_ops vdpasim_net_batch_config_ops;

static struct vdpasim *vdpasim_create(void)
{
        const struct vdpa_config_ops *ops;
        struct vdpasim *vdpasim;
        struct device *dev;
        int ret = -ENOMEM;

        if (batch_mapping)
                ops = &vdpasim_net_batch_config_ops;
        else
                ops = &vdpasim_net_config_ops;

        vdpasim = vdpa_alloc_device(struct vdpasim, vdpa, NULL, ops, VDPASIM_VQ_NUM);
        if (!vdpasim)
                goto err_alloc;

        INIT_WORK(&vdpasim->work, vdpasim_work);
        spin_lock_init(&vdpasim->lock);
        spin_lock_init(&vdpasim->iommu_lock);

        dev = &vdpasim->vdpa.dev;
        dev->coherent_dma_mask = DMA_BIT_MASK(64);
        set_dma_ops(dev, &vdpasim_dma_ops);

        vdpasim->iommu = vhost_iotlb_alloc(2048, 0);
        if (!vdpasim->iommu)
                goto err_iommu;

        vdpasim->buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
        if (!vdpasim->buffer)
                goto err_iommu;

        eth_random_addr(vdpasim->config.mac);

        vringh_set_iotlb(&vdpasim->vqs[0].vring, vdpasim->iommu);
        vringh_set_iotlb(&vdpasim->vqs[1].vring, vdpasim->iommu);

        vdpasim->vdpa.dma_dev = dev;
        ret = vdpa_register_device(&vdpasim->vdpa);
        if (ret)
                goto err_iommu;

        return vdpasim;

err_iommu:
        put_device(dev);
err_alloc:
        return ERR_PTR(ret);
}

static int vdpasim_set_vq_address(struct vdpa_device *vdpa, u16 idx,
                                  u64 desc_area, u64 driver_area,
                                  u64 device_area)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];

        vq->desc_addr = desc_area;
        vq->driver_addr = driver_area;
        vq->device_addr = device_area;

        return 0;
}

static void vdpasim_set_vq_num(struct vdpa_device *vdpa, u16 idx, u32 num)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];

        vq->num = num;
}

static void vdpasim_kick_vq(struct vdpa_device *vdpa, u16 idx)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];

        if (vq->ready)
                schedule_work(&vdpasim->work);
}

static void vdpasim_set_vq_cb(struct vdpa_device *vdpa, u16 idx,
                              struct vdpa_callback *cb)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];

        vq->cb = cb->callback;
        vq->private = cb->private;
}

static void vdpasim_set_vq_ready(struct vdpa_device *vdpa, u16 idx, bool ready)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];

        spin_lock(&vdpasim->lock);
        vq->ready = ready;
        if (vq->ready)
                vdpasim_queue_ready(vdpasim, idx);
        spin_unlock(&vdpasim->lock);
}

static bool vdpasim_get_vq_ready(struct vdpa_device *vdpa, u16 idx)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];

        return vq->ready;
}

static int vdpasim_set_vq_state(struct vdpa_device *vdpa, u16 idx,
                                const struct vdpa_vq_state *state)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
        struct vringh *vrh = &vq->vring;

        spin_lock(&vdpasim->lock);
        vrh->last_avail_idx = state->avail_index;
        spin_unlock(&vdpasim->lock);

        return 0;
}

static int vdpasim_get_vq_state(struct vdpa_device *vdpa, u16 idx,
                                struct vdpa_vq_state *state)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
        struct vringh *vrh = &vq->vring;

        state->avail_index = vrh->last_avail_idx;
        return 0;
}

static u32 vdpasim_get_vq_align(struct vdpa_device *vdpa)
{
        return VDPASIM_QUEUE_ALIGN;
}

static u64 vdpasim_get_features(struct vdpa_device *vdpa)
{
        return vdpasim_features;
}

static int vdpasim_set_features(struct vdpa_device *vdpa, u64 features)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        struct virtio_net_config *config = &vdpasim->config;

        /* DMA mapping must be done by driver */
        if (!(features & (1ULL << VIRTIO_F_ACCESS_PLATFORM)))
                return -EINVAL;

        vdpasim->features = features & vdpasim_features;

        /* We generally only know whether guest is using the legacy interface
         * here, so generally that's the earliest we can set config fields.
         * Note: We actually require VIRTIO_F_ACCESS_PLATFORM above which
         * implies VIRTIO_F_VERSION_1, but let's not try to be clever here.
         */

        config->mtu = cpu_to_vdpasim16(vdpasim, 1500);
        config->status = cpu_to_vdpasim16(vdpasim, VIRTIO_NET_S_LINK_UP);
        return 0;
}

static void vdpasim_set_config_cb(struct vdpa_device *vdpa,
                                  struct vdpa_callback *cb)
{
        /* We don't support config interrupt */
}

static u16 vdpasim_get_vq_num_max(struct vdpa_device *vdpa)
{
        return VDPASIM_QUEUE_MAX;
}

static u32 vdpasim_get_device_id(struct vdpa_device *vdpa)
{
        return VDPASIM_DEVICE_ID;
}

static u32 vdpasim_get_vendor_id(struct vdpa_device *vdpa)
{
        return VDPASIM_VENDOR_ID;
}

static u8 vdpasim_get_status(struct vdpa_device *vdpa)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        u8 status;

        spin_lock(&vdpasim->lock);
        status = vdpasim->status;
        spin_unlock(&vdpasim->lock);

        return status;
}

static void vdpasim_set_status(struct vdpa_device *vdpa, u8 status)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);

        spin_lock(&vdpasim->lock);
        vdpasim->status = status;
        if (status == 0)
                vdpasim_reset(vdpasim);
        spin_unlock(&vdpasim->lock);
}

static void vdpasim_get_config(struct vdpa_device *vdpa, unsigned int offset,
                             void *buf, unsigned int len)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);

        if (offset + len < sizeof(struct virtio_net_config))
                memcpy(buf, (u8 *)&vdpasim->config + offset, len);
}

static void vdpasim_set_config(struct vdpa_device *vdpa, unsigned int offset,
                             const void *buf, unsigned int len)
{
        /* No writable config supportted by vdpasim */
}

static u32 vdpasim_get_generation(struct vdpa_device *vdpa)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);

        return vdpasim->generation;
}

static int vdpasim_set_map(struct vdpa_device *vdpa,
                           struct vhost_iotlb *iotlb)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        struct vhost_iotlb_map *map;
        u64 start = 0ULL, last = 0ULL - 1;
        int ret;

        spin_lock(&vdpasim->iommu_lock);
        vhost_iotlb_reset(vdpasim->iommu);

        for (map = vhost_iotlb_itree_first(iotlb, start, last); map;
             map = vhost_iotlb_itree_next(map, start, last)) {
                ret = vhost_iotlb_add_range(vdpasim->iommu, map->start,
                                            map->last, map->addr, map->perm);
                if (ret)
                        goto err;
        }
        spin_unlock(&vdpasim->iommu_lock);
        return 0;

err:
        vhost_iotlb_reset(vdpasim->iommu);
        spin_unlock(&vdpasim->iommu_lock);
        return ret;
}

static int vdpasim_dma_map(struct vdpa_device *vdpa, u64 iova, u64 size,
                           u64 pa, u32 perm)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
        int ret;

        spin_lock(&vdpasim->iommu_lock);
        ret = vhost_iotlb_add_range(vdpasim->iommu, iova, iova + size - 1, pa,
                                    perm);
        spin_unlock(&vdpasim->iommu_lock);

        return ret;
}

static int vdpasim_dma_unmap(struct vdpa_device *vdpa, u64 iova, u64 size)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);

        spin_lock(&vdpasim->iommu_lock);
        vhost_iotlb_del_range(vdpasim->iommu, iova, iova + size - 1);
        spin_unlock(&vdpasim->iommu_lock);

        return 0;
}

static void vdpasim_free(struct vdpa_device *vdpa)
{
        struct vdpasim *vdpasim = vdpa_to_sim(vdpa);

        cancel_work_sync(&vdpasim->work);
        kfree(vdpasim->buffer);
        if (vdpasim->iommu)
                vhost_iotlb_free(vdpasim->iommu);
}

static const struct vdpa_config_ops vdpasim_net_config_ops = {
        .set_vq_address         = vdpasim_set_vq_address,
        .set_vq_num             = vdpasim_set_vq_num,
        .kick_vq                = vdpasim_kick_vq,
        .set_vq_cb              = vdpasim_set_vq_cb,
        .set_vq_ready           = vdpasim_set_vq_ready,
        .get_vq_ready           = vdpasim_get_vq_ready,
        .set_vq_state           = vdpasim_set_vq_state,
        .get_vq_state           = vdpasim_get_vq_state,
        .get_vq_align           = vdpasim_get_vq_align,
        .get_features           = vdpasim_get_features,
        .set_features           = vdpasim_set_features,
        .set_config_cb          = vdpasim_set_config_cb,
        .get_vq_num_max         = vdpasim_get_vq_num_max,
        .get_device_id          = vdpasim_get_device_id,
        .get_vendor_id          = vdpasim_get_vendor_id,
        .get_status             = vdpasim_get_status,
        .set_status             = vdpasim_set_status,
        .get_config             = vdpasim_get_config,
        .set_config             = vdpasim_set_config,
        .get_generation         = vdpasim_get_generation,
        .dma_map                = vdpasim_dma_map,
        .dma_unmap              = vdpasim_dma_unmap,
        .free                   = vdpasim_free,
};

static const struct vdpa_config_ops vdpasim_net_batch_config_ops = {
        .set_vq_address         = vdpasim_set_vq_address,
        .set_vq_num             = vdpasim_set_vq_num,
        .kick_vq                = vdpasim_kick_vq,
        .set_vq_cb              = vdpasim_set_vq_cb,
        .set_vq_ready           = vdpasim_set_vq_ready,
        .get_vq_ready           = vdpasim_get_vq_ready,
        .set_vq_state           = vdpasim_set_vq_state,
        .get_vq_state           = vdpasim_get_vq_state,
        .get_vq_align           = vdpasim_get_vq_align,
        .get_features           = vdpasim_get_features,
        .set_features           = vdpasim_set_features,
        .set_config_cb          = vdpasim_set_config_cb,
        .get_vq_num_max         = vdpasim_get_vq_num_max,
        .get_device_id          = vdpasim_get_device_id,
        .get_vendor_id          = vdpasim_get_vendor_id,
        .get_status             = vdpasim_get_status,
        .set_status             = vdpasim_set_status,
        .get_config             = vdpasim_get_config,
        .set_config             = vdpasim_set_config,
        .get_generation         = vdpasim_get_generation,
        .set_map                = vdpasim_set_map,
        .free                   = vdpasim_free,
};

static int __init vdpasim_dev_init(void)
{
        vdpasim_dev = vdpasim_create();

        if (!IS_ERR(vdpasim_dev))
                return 0;

        return PTR_ERR(vdpasim_dev);
}

static void __exit vdpasim_dev_exit(void)
{
        struct vdpa_device *vdpa = &vdpasim_dev->vdpa;

        vdpa_unregister_device(vdpa);
}

module_init(vdpasim_dev_init)
module_exit(vdpasim_dev_exit)

MODULE_VERSION(DRV_VERSION);
MODULE_LICENSE(DRV_LICENSE);
MODULE_AUTHOR(DRV_AUTHOR);
MODULE_DESCRIPTION(DRV_DESC);