// SPDX-License-Identifier: GPL-2.0
/*
 * Virtio driver for the paravirtualized IOMMU
 *
 * Copyright (C) 2019 Arm Limited
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/delay.h>
#include <linux/dma-map-ops.h>
#include <linux/freezer.h>
#include <linux/interval_tree.h>
#include <linux/iommu.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/pci.h>
#include <linux/virtio.h>
#include <linux/virtio_config.h>
#include <linux/virtio_ids.h>
#include <linux/wait.h>

#include <uapi/linux/virtio_iommu.h>

#include "dma-iommu.h"

#define MSI_IOVA_BASE                   0x8000000
#define MSI_IOVA_LENGTH                 0x100000

#define VIOMMU_REQUEST_VQ               0
#define VIOMMU_EVENT_VQ                 1
#define VIOMMU_NR_VQS                   2

struct viommu_dev {
        struct iommu_device             iommu;
        struct device                   *dev;
        struct virtio_device            *vdev;

        struct ida                      domain_ids;

        struct virtqueue                *vqs[VIOMMU_NR_VQS];
        spinlock_t                      request_lock;
        struct list_head                requests;
        void                            *evts;

        /* Device configuration */
        struct iommu_domain_geometry    geometry;
        u64                             pgsize_bitmap;
        u32                             first_domain;
        u32                             last_domain;
        u32                             identity_domain_id;
        /* Supported MAP flags */
        u32                             map_flags;
        u32                             probe_size;
};

struct viommu_mapping {
        phys_addr_t                     paddr;
        struct interval_tree_node       iova;
        u32                             flags;
};

struct viommu_domain {
        struct iommu_domain             domain;
        struct viommu_dev               *viommu;
        unsigned int                    id;
        u32                             map_flags;

        spinlock_t                      mappings_lock;
        struct rb_root_cached           mappings;

        unsigned long                   nr_endpoints;
};

struct viommu_endpoint {
        struct device                   *dev;
        struct viommu_dev               *viommu;
        struct viommu_domain            *vdomain;
        struct list_head                resv_regions;
};

struct viommu_request {
        struct list_head                list;
        void                            *writeback;
        unsigned int                    write_offset;
        unsigned int                    len;
        char                            buf[] __counted_by(len);
};

#define VIOMMU_FAULT_RESV_MASK          0xffffff00

struct viommu_event {
        union {
                u32                     head;
                struct virtio_iommu_fault fault;
        };
};

static struct viommu_domain viommu_identity_domain;

#define to_viommu_domain(domain)        \
        container_of(domain, struct viommu_domain, domain)

static int viommu_get_req_errno(void *buf, size_t len)
{
        struct virtio_iommu_req_tail *tail = buf + len - sizeof(*tail);

        switch (tail->status) {
        case VIRTIO_IOMMU_S_OK:
                return 0;
        case VIRTIO_IOMMU_S_UNSUPP:
                return -ENOSYS;
        case VIRTIO_IOMMU_S_INVAL:
                return -EINVAL;
        case VIRTIO_IOMMU_S_RANGE:
                return -ERANGE;
        case VIRTIO_IOMMU_S_NOENT:
                return -ENOENT;
        case VIRTIO_IOMMU_S_FAULT:
                return -EFAULT;
        case VIRTIO_IOMMU_S_NOMEM:
                return -ENOMEM;
        case VIRTIO_IOMMU_S_IOERR:
        case VIRTIO_IOMMU_S_DEVERR:
        default:
                return -EIO;
        }
}

static void viommu_set_req_status(void *buf, size_t len, int status)
{
        struct virtio_iommu_req_tail *tail = buf + len - sizeof(*tail);

        tail->status = status;
}

static off_t viommu_get_write_desc_offset(struct viommu_dev *viommu,
                                          struct virtio_iommu_req_head *req,
                                          size_t len)
{
        size_t tail_size = sizeof(struct virtio_iommu_req_tail);

        if (req->type == VIRTIO_IOMMU_T_PROBE)
                return len - viommu->probe_size - tail_size;

        return len - tail_size;
}

/*
 * __viommu_sync_req - Complete all in-flight requests
 *
 * Wait for all added requests to complete. When this function returns, all
 * requests that were in-flight at the time of the call have completed.
 */
static int __viommu_sync_req(struct viommu_dev *viommu)
{
        unsigned int len;
        size_t write_len;
        struct viommu_request *req;
        struct virtqueue *vq = viommu->vqs[VIOMMU_REQUEST_VQ];

        assert_spin_locked(&viommu->request_lock);

        virtqueue_kick(vq);

        while (!list_empty(&viommu->requests)) {
                len = 0;
                req = virtqueue_get_buf(vq, &len);
                if (!req)
                        continue;

                if (!len)
                        viommu_set_req_status(req->buf, req->len,
                                              VIRTIO_IOMMU_S_IOERR);

                write_len = req->len - req->write_offset;
                if (req->writeback && len == write_len)
                        memcpy(req->writeback, req->buf + req->write_offset,
                               write_len);

                list_del(&req->list);
                kfree(req);
        }

        return 0;
}

static int viommu_sync_req(struct viommu_dev *viommu)
{
        int ret;
        unsigned long flags;

        spin_lock_irqsave(&viommu->request_lock, flags);
        ret = __viommu_sync_req(viommu);
        if (ret)
                dev_dbg(viommu->dev, "could not sync requests (%d)\n", ret);
        spin_unlock_irqrestore(&viommu->request_lock, flags);

        return ret;
}

/*
 * __viommu_add_request - Add one request to the queue
 * @buf: pointer to the request buffer
 * @len: length of the request buffer
 * @writeback: copy data back to the buffer when the request completes.
 *
 * Add a request to the queue. Only synchronize the queue if it's already full.
 * Otherwise don't kick the queue nor wait for requests to complete.
 *
 * When @writeback is true, data written by the device, including the request
 * status, is copied into @buf after the request completes. This is unsafe if
 * the caller allocates @buf on stack and drops the lock between add_req() and
 * sync_req().
 *
 * Return 0 if the request was successfully added to the queue.
 */
static int __viommu_add_req(struct viommu_dev *viommu, void *buf, size_t len,
                            bool writeback)
{
        int ret;
        off_t write_offset;
        struct viommu_request *req;
        struct scatterlist top_sg, bottom_sg;
        struct scatterlist *sg[2] = { &top_sg, &bottom_sg };
        struct virtqueue *vq = viommu->vqs[VIOMMU_REQUEST_VQ];

        assert_spin_locked(&viommu->request_lock);

        write_offset = viommu_get_write_desc_offset(viommu, buf, len);
        if (write_offset <= 0)
                return -EINVAL;

        req = kzalloc_flex(*req, buf, len, GFP_ATOMIC);
        if (!req)
                return -ENOMEM;

        req->len = len;
        if (writeback) {
                req->writeback = buf + write_offset;
                req->write_offset = write_offset;
        }
        memcpy(&req->buf, buf, write_offset);

        sg_init_one(&top_sg, req->buf, write_offset);
        sg_init_one(&bottom_sg, req->buf + write_offset, len - write_offset);

        ret = virtqueue_add_sgs(vq, sg, 1, 1, req, GFP_ATOMIC);
        if (ret == -ENOSPC) {
                /* If the queue is full, sync and retry */
                if (!__viommu_sync_req(viommu))
                        ret = virtqueue_add_sgs(vq, sg, 1, 1, req, GFP_ATOMIC);
        }
        if (ret)
                goto err_free;

        list_add_tail(&req->list, &viommu->requests);
        return 0;

err_free:
        kfree(req);
        return ret;
}

static int viommu_add_req(struct viommu_dev *viommu, void *buf, size_t len)
{
        int ret;
        unsigned long flags;

        spin_lock_irqsave(&viommu->request_lock, flags);
        ret = __viommu_add_req(viommu, buf, len, false);
        if (ret)
                dev_dbg(viommu->dev, "could not add request: %d\n", ret);
        spin_unlock_irqrestore(&viommu->request_lock, flags);

        return ret;
}

/*
 * Send a request and wait for it to complete. Return the request status (as an
 * errno)
 */
static int viommu_send_req_sync(struct viommu_dev *viommu, void *buf,
                                size_t len)
{
        int ret;
        unsigned long flags;

        spin_lock_irqsave(&viommu->request_lock, flags);

        ret = __viommu_add_req(viommu, buf, len, true);
        if (ret) {
                dev_dbg(viommu->dev, "could not add request (%d)\n", ret);
                goto out_unlock;
        }

        ret = __viommu_sync_req(viommu);
        if (ret) {
                dev_dbg(viommu->dev, "could not sync requests (%d)\n", ret);
                /* Fall-through (get the actual request status) */
        }

        ret = viommu_get_req_errno(buf, len);
out_unlock:
        spin_unlock_irqrestore(&viommu->request_lock, flags);
        return ret;
}

static int viommu_send_attach_req(struct viommu_dev *viommu, struct device *dev,
                                  struct virtio_iommu_req_attach *req)
{
        int ret;
        unsigned int i;
        struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);

        for (i = 0; i < fwspec->num_ids; i++) {
                req->endpoint = cpu_to_le32(fwspec->ids[i]);
                ret = viommu_send_req_sync(viommu, req, sizeof(*req));
                if (ret)
                        return ret;
        }
        return 0;
}

/*
 * viommu_add_mapping - add a mapping to the internal tree
 *
 * On success, return the new mapping. Otherwise return NULL.
 */
static int viommu_add_mapping(struct viommu_domain *vdomain, u64 iova, u64 end,
                              phys_addr_t paddr, u32 flags)
{
        unsigned long irqflags;
        struct viommu_mapping *mapping;

        mapping = kzalloc_obj(*mapping, GFP_ATOMIC);
        if (!mapping)
                return -ENOMEM;

        mapping->paddr          = paddr;
        mapping->iova.start     = iova;
        mapping->iova.last      = end;
        mapping->flags          = flags;

        spin_lock_irqsave(&vdomain->mappings_lock, irqflags);
        interval_tree_insert(&mapping->iova, &vdomain->mappings);
        spin_unlock_irqrestore(&vdomain->mappings_lock, irqflags);

        return 0;
}

/*
 * viommu_del_mappings - remove mappings from the internal tree
 *
 * @vdomain: the domain
 * @iova: start of the range
 * @end: end of the range
 *
 * On success, returns the number of unmapped bytes
 */
static size_t viommu_del_mappings(struct viommu_domain *vdomain,
                                  u64 iova, u64 end)
{
        size_t unmapped = 0;
        unsigned long flags;
        struct viommu_mapping *mapping = NULL;
        struct interval_tree_node *node, *next;

        spin_lock_irqsave(&vdomain->mappings_lock, flags);
        next = interval_tree_iter_first(&vdomain->mappings, iova, end);
        while (next) {
                node = next;
                mapping = container_of(node, struct viommu_mapping, iova);
                next = interval_tree_iter_next(node, iova, end);

                /* Trying to split a mapping? */
                if (mapping->iova.start < iova)
                        break;

                /*
                 * Virtio-iommu doesn't allow UNMAP to split a mapping created
                 * with a single MAP request, so remove the full mapping.
                 */
                unmapped += mapping->iova.last - mapping->iova.start + 1;

                interval_tree_remove(node, &vdomain->mappings);
                kfree(mapping);
        }
        spin_unlock_irqrestore(&vdomain->mappings_lock, flags);

        return unmapped;
}

/*
 * Fill the domain with identity mappings, skipping the device's reserved
 * regions.
 */
static int viommu_domain_map_identity(struct viommu_endpoint *vdev,
                                      struct viommu_domain *vdomain)
{
        int ret;
        struct iommu_resv_region *resv;
        u64 iova = vdomain->domain.geometry.aperture_start;
        u64 limit = vdomain->domain.geometry.aperture_end;
        u32 flags = VIRTIO_IOMMU_MAP_F_READ | VIRTIO_IOMMU_MAP_F_WRITE;
        unsigned long granule = 1UL << __ffs(vdomain->domain.pgsize_bitmap);

        iova = ALIGN(iova, granule);
        limit = ALIGN_DOWN(limit + 1, granule) - 1;

        list_for_each_entry(resv, &vdev->resv_regions, list) {
                u64 resv_start = ALIGN_DOWN(resv->start, granule);
                u64 resv_end = ALIGN(resv->start + resv->length, granule) - 1;

                if (resv_end < iova || resv_start > limit)
                        /* No overlap */
                        continue;

                if (resv_start > iova) {
                        ret = viommu_add_mapping(vdomain, iova, resv_start - 1,
                                                 (phys_addr_t)iova, flags);
                        if (ret)
                                goto err_unmap;
                }

                if (resv_end >= limit)
                        return 0;

                iova = resv_end + 1;
        }

        ret = viommu_add_mapping(vdomain, iova, limit, (phys_addr_t)iova,
                                 flags);
        if (ret)
                goto err_unmap;
        return 0;

err_unmap:
        viommu_del_mappings(vdomain, 0, iova);
        return ret;
}

/*
 * viommu_replay_mappings - re-send MAP requests
 *
 * When reattaching a domain that was previously detached from all endpoints,
 * mappings were deleted from the device. Re-create the mappings available in
 * the internal tree.
 */
static int viommu_replay_mappings(struct viommu_domain *vdomain)
{
        int ret = 0;
        unsigned long flags;
        struct viommu_mapping *mapping;
        struct interval_tree_node *node;
        struct virtio_iommu_req_map map;

        spin_lock_irqsave(&vdomain->mappings_lock, flags);
        node = interval_tree_iter_first(&vdomain->mappings, 0, -1UL);
        while (node) {
                mapping = container_of(node, struct viommu_mapping, iova);
                map = (struct virtio_iommu_req_map) {
                        .head.type      = VIRTIO_IOMMU_T_MAP,
                        .domain         = cpu_to_le32(vdomain->id),
                        .virt_start     = cpu_to_le64(mapping->iova.start),
                        .virt_end       = cpu_to_le64(mapping->iova.last),
                        .phys_start     = cpu_to_le64(mapping->paddr),
                        .flags          = cpu_to_le32(mapping->flags),
                };

                ret = viommu_send_req_sync(vdomain->viommu, &map, sizeof(map));
                if (ret)
                        break;

                node = interval_tree_iter_next(node, 0, -1UL);
        }
        spin_unlock_irqrestore(&vdomain->mappings_lock, flags);

        return ret;
}

static int viommu_add_resv_mem(struct viommu_endpoint *vdev,
                               struct virtio_iommu_probe_resv_mem *mem,
                               size_t len)
{
        size_t size;
        u64 start64, end64;
        phys_addr_t start, end;
        struct iommu_resv_region *region = NULL, *next;
        unsigned long prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;

        start = start64 = le64_to_cpu(mem->start);
        end = end64 = le64_to_cpu(mem->end);
        size = end64 - start64 + 1;

        /* Catch any overflow, including the unlikely end64 - start64 + 1 = 0 */
        if (start != start64 || end != end64 || size < end64 - start64)
                return -EOVERFLOW;

        if (len < sizeof(*mem))
                return -EINVAL;

        switch (mem->subtype) {
        default:
                dev_warn(vdev->dev, "unknown resv mem subtype 0x%x\n",
                         mem->subtype);
                fallthrough;
        case VIRTIO_IOMMU_RESV_MEM_T_RESERVED:
                region = iommu_alloc_resv_region(start, size, 0,
                                                 IOMMU_RESV_RESERVED,
                                                 GFP_KERNEL);
                break;
        case VIRTIO_IOMMU_RESV_MEM_T_MSI:
                region = iommu_alloc_resv_region(start, size, prot,
                                                 IOMMU_RESV_MSI,
                                                 GFP_KERNEL);
                break;
        }
        if (!region)
                return -ENOMEM;

        /* Keep the list sorted */
        list_for_each_entry(next, &vdev->resv_regions, list) {
                if (next->start > region->start)
                        break;
        }
        list_add_tail(&region->list, &next->list);
        return 0;
}

static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device *dev)
{
        int ret;
        u16 type, len;
        size_t cur = 0;
        size_t probe_len;
        struct virtio_iommu_req_probe *probe;
        struct virtio_iommu_probe_property *prop;
        struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
        struct viommu_endpoint *vdev = dev_iommu_priv_get(dev);

        if (!fwspec->num_ids)
                return -EINVAL;

        probe_len = sizeof(*probe) + viommu->probe_size +
                    sizeof(struct virtio_iommu_req_tail);
        probe = kzalloc(probe_len, GFP_KERNEL);
        if (!probe)
                return -ENOMEM;

        probe->head.type = VIRTIO_IOMMU_T_PROBE;
        /*
         * For now, assume that properties of an endpoint that outputs multiple
         * IDs are consistent. Only probe the first one.
         */
        probe->endpoint = cpu_to_le32(fwspec->ids[0]);

        ret = viommu_send_req_sync(viommu, probe, probe_len);
        if (ret)
                goto out_free;

        prop = (void *)probe->properties;
        type = le16_to_cpu(prop->type) & VIRTIO_IOMMU_PROBE_T_MASK;

        while (type != VIRTIO_IOMMU_PROBE_T_NONE &&
               cur < viommu->probe_size) {
                len = le16_to_cpu(prop->length) + sizeof(*prop);

                switch (type) {
                case VIRTIO_IOMMU_PROBE_T_RESV_MEM:
                        ret = viommu_add_resv_mem(vdev, (void *)prop, len);
                        break;
                default:
                        dev_err(dev, "unknown viommu prop 0x%x\n", type);
                }

                if (ret)
                        dev_err(dev, "failed to parse viommu prop 0x%x\n", type);

                cur += len;
                if (cur >= viommu->probe_size)
                        break;

                prop = (void *)probe->properties + cur;
                type = le16_to_cpu(prop->type) & VIRTIO_IOMMU_PROBE_T_MASK;
        }

out_free:
        kfree(probe);
        return ret;
}

static int viommu_fault_handler(struct viommu_dev *viommu,
                                struct virtio_iommu_fault *fault)
{
        char *reason_str;

        u8 reason       = fault->reason;
        u32 flags       = le32_to_cpu(fault->flags);
        u32 endpoint    = le32_to_cpu(fault->endpoint);
        u64 address     = le64_to_cpu(fault->address);

        switch (reason) {
        case VIRTIO_IOMMU_FAULT_R_DOMAIN:
                reason_str = "domain";
                break;
        case VIRTIO_IOMMU_FAULT_R_MAPPING:
                reason_str = "page";
                break;
        case VIRTIO_IOMMU_FAULT_R_UNKNOWN:
        default:
                reason_str = "unknown";
                break;
        }

        /* TODO: find EP by ID and report_iommu_fault */
        if (flags & VIRTIO_IOMMU_FAULT_F_ADDRESS)
                dev_err_ratelimited(viommu->dev, "%s fault from EP %u at %#llx [%s%s%s]\n",
                                    reason_str, endpoint, address,
                                    flags & VIRTIO_IOMMU_FAULT_F_READ ? "R" : "",
                                    flags & VIRTIO_IOMMU_FAULT_F_WRITE ? "W" : "",
                                    flags & VIRTIO_IOMMU_FAULT_F_EXEC ? "X" : "");
        else
                dev_err_ratelimited(viommu->dev, "%s fault from EP %u\n",
                                    reason_str, endpoint);
        return 0;
}

static void viommu_event_handler(struct virtqueue *vq)
{
        int ret;
        unsigned int len;
        struct scatterlist sg[1];
        struct viommu_event *evt;
        struct viommu_dev *viommu = vq->vdev->priv;

        while ((evt = virtqueue_get_buf(vq, &len)) != NULL) {
                if (len > sizeof(*evt)) {
                        dev_err(viommu->dev,
                                "invalid event buffer (len %u != %zu)\n",
                                len, sizeof(*evt));
                } else if (!(evt->head & VIOMMU_FAULT_RESV_MASK)) {
                        viommu_fault_handler(viommu, &evt->fault);
                }

                sg_init_one(sg, evt, sizeof(*evt));
                ret = virtqueue_add_inbuf(vq, sg, 1, evt, GFP_ATOMIC);
                if (ret)
                        dev_err(viommu->dev, "could not add event buffer\n");
        }

        virtqueue_kick(vq);
}

/* IOMMU API */

static struct iommu_domain *viommu_domain_alloc_paging(struct device *dev)
{
        struct viommu_endpoint *vdev = dev_iommu_priv_get(dev);
        struct viommu_dev *viommu = vdev->viommu;
        unsigned long viommu_page_size;
        struct viommu_domain *vdomain;
        int ret;

        viommu_page_size = 1UL << __ffs(viommu->pgsize_bitmap);
        if (viommu_page_size > PAGE_SIZE) {
                dev_err(vdev->dev,
                        "granule 0x%lx larger than system page size 0x%lx\n",
                        viommu_page_size, PAGE_SIZE);
                return ERR_PTR(-ENODEV);
        }

        vdomain = kzalloc_obj(*vdomain);
        if (!vdomain)
                return ERR_PTR(-ENOMEM);

        spin_lock_init(&vdomain->mappings_lock);
        vdomain->mappings = RB_ROOT_CACHED;

        ret = ida_alloc_range(&viommu->domain_ids, viommu->first_domain,
                              viommu->last_domain, GFP_KERNEL);
        if (ret < 0) {
                kfree(vdomain);
                return ERR_PTR(ret);
        }

        vdomain->id = (unsigned int)ret;

        vdomain->domain.pgsize_bitmap = viommu->pgsize_bitmap;
        vdomain->domain.geometry = viommu->geometry;

        vdomain->map_flags = viommu->map_flags;
        vdomain->viommu = viommu;

        return &vdomain->domain;
}

static void viommu_domain_free(struct iommu_domain *domain)
{
        struct viommu_domain *vdomain = to_viommu_domain(domain);

        /* Free all remaining mappings */
        viommu_del_mappings(vdomain, 0, ULLONG_MAX);

        if (vdomain->viommu)
                ida_free(&vdomain->viommu->domain_ids, vdomain->id);

        kfree(vdomain);
}

static struct iommu_domain *viommu_domain_alloc_identity(struct device *dev)
{
        struct viommu_endpoint *vdev = dev_iommu_priv_get(dev);
        struct iommu_domain *domain;
        int ret;

        if (virtio_has_feature(vdev->viommu->vdev,
                               VIRTIO_IOMMU_F_BYPASS_CONFIG))
                return &viommu_identity_domain.domain;

        domain = viommu_domain_alloc_paging(dev);
        if (IS_ERR(domain))
                return domain;

        ret = viommu_domain_map_identity(vdev, to_viommu_domain(domain));
        if (ret) {
                viommu_domain_free(domain);
                return ERR_PTR(ret);
        }
        return domain;
}

static int viommu_attach_dev(struct iommu_domain *domain, struct device *dev,
                             struct iommu_domain *old)
{
        int ret = 0;
        struct virtio_iommu_req_attach req;
        struct viommu_endpoint *vdev = dev_iommu_priv_get(dev);
        struct viommu_domain *vdomain = to_viommu_domain(domain);

        if (vdomain->viommu != vdev->viommu)
                return -EINVAL;

        /*
         * In the virtio-iommu device, when attaching the endpoint to a new
         * domain, it is detached from the old one and, if as a result the
         * old domain isn't attached to any endpoint, all mappings are removed
         * from the old domain and it is freed.
         *
         * In the driver the old domain still exists, and its mappings will be
         * recreated if it gets reattached to an endpoint. Otherwise it will be
         * freed explicitly.
         *
         * vdev->vdomain is protected by group->mutex
         */
        if (vdev->vdomain)
                vdev->vdomain->nr_endpoints--;

        req = (struct virtio_iommu_req_attach) {
                .head.type      = VIRTIO_IOMMU_T_ATTACH,
                .domain         = cpu_to_le32(vdomain->id),
        };

        ret = viommu_send_attach_req(vdomain->viommu, dev, &req);
        if (ret)
                return ret;

        if (!vdomain->nr_endpoints) {
                /*
                 * This endpoint is the first to be attached to the domain.
                 * Replay existing mappings (e.g. SW MSI).
                 */
                ret = viommu_replay_mappings(vdomain);
                if (ret)
                        return ret;
        }

        vdomain->nr_endpoints++;
        vdev->vdomain = vdomain;

        return 0;
}

static int viommu_attach_identity_domain(struct iommu_domain *domain,
                                         struct device *dev,
                                         struct iommu_domain *old)
{
        int ret = 0;
        struct virtio_iommu_req_attach req;
        struct viommu_endpoint *vdev = dev_iommu_priv_get(dev);
        struct viommu_domain *vdomain = to_viommu_domain(domain);

        req = (struct virtio_iommu_req_attach) {
                .head.type      = VIRTIO_IOMMU_T_ATTACH,
                .domain         = cpu_to_le32(vdev->viommu->identity_domain_id),
                .flags          = cpu_to_le32(VIRTIO_IOMMU_ATTACH_F_BYPASS),
        };

        ret = viommu_send_attach_req(vdev->viommu, dev, &req);
        if (ret)
                return ret;

        if (vdev->vdomain)
                vdev->vdomain->nr_endpoints--;
        vdomain->nr_endpoints++;
        vdev->vdomain = vdomain;
        return 0;
}

static struct viommu_domain viommu_identity_domain = {
        .domain = {
                .type = IOMMU_DOMAIN_IDENTITY,
                .ops = &(const struct iommu_domain_ops) {
                        .attach_dev = viommu_attach_identity_domain,
                },
        },
};

static void viommu_detach_dev(struct viommu_endpoint *vdev)
{
        int i;
        struct virtio_iommu_req_detach req;
        struct viommu_domain *vdomain = vdev->vdomain;
        struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(vdev->dev);

        if (!vdomain)
                return;

        req = (struct virtio_iommu_req_detach) {
                .head.type      = VIRTIO_IOMMU_T_DETACH,
                .domain         = cpu_to_le32(vdomain->id),
        };

        for (i = 0; i < fwspec->num_ids; i++) {
                req.endpoint = cpu_to_le32(fwspec->ids[i]);
                WARN_ON(viommu_send_req_sync(vdev->viommu, &req, sizeof(req)));
        }
        vdomain->nr_endpoints--;
        vdev->vdomain = NULL;
}

static int viommu_map_pages(struct iommu_domain *domain, unsigned long iova,
                            phys_addr_t paddr, size_t pgsize, size_t pgcount,
                            int prot, gfp_t gfp, size_t *mapped)
{
        int ret;
        u32 flags;
        size_t size = pgsize * pgcount;
        u64 end = iova + size - 1;
        struct virtio_iommu_req_map map;
        struct viommu_domain *vdomain = to_viommu_domain(domain);

        flags = (prot & IOMMU_READ ? VIRTIO_IOMMU_MAP_F_READ : 0) |
                (prot & IOMMU_WRITE ? VIRTIO_IOMMU_MAP_F_WRITE : 0) |
                (prot & IOMMU_MMIO ? VIRTIO_IOMMU_MAP_F_MMIO : 0);

        if (flags & ~vdomain->map_flags)
                return -EINVAL;

        ret = viommu_add_mapping(vdomain, iova, end, paddr, flags);
        if (ret)
                return ret;

        if (vdomain->nr_endpoints) {
                map = (struct virtio_iommu_req_map) {
                        .head.type      = VIRTIO_IOMMU_T_MAP,
                        .domain         = cpu_to_le32(vdomain->id),
                        .virt_start     = cpu_to_le64(iova),
                        .phys_start     = cpu_to_le64(paddr),
                        .virt_end       = cpu_to_le64(end),
                        .flags          = cpu_to_le32(flags),
                };

                ret = viommu_add_req(vdomain->viommu, &map, sizeof(map));
                if (ret) {
                        viommu_del_mappings(vdomain, iova, end);
                        return ret;
                }
        }
        if (mapped)
                *mapped = size;

        return 0;
}

static size_t viommu_unmap_pages(struct iommu_domain *domain, unsigned long iova,
                                 size_t pgsize, size_t pgcount,
                                 struct iommu_iotlb_gather *gather)
{
        int ret = 0;
        size_t unmapped;
        struct virtio_iommu_req_unmap unmap;
        struct viommu_domain *vdomain = to_viommu_domain(domain);
        size_t size = pgsize * pgcount;

        unmapped = viommu_del_mappings(vdomain, iova, iova + size - 1);
        if (unmapped < size)
                return 0;

        /* Device already removed all mappings after detach. */
        if (!vdomain->nr_endpoints)
                return unmapped;

        unmap = (struct virtio_iommu_req_unmap) {
                .head.type      = VIRTIO_IOMMU_T_UNMAP,
                .domain         = cpu_to_le32(vdomain->id),
                .virt_start     = cpu_to_le64(iova),
                .virt_end       = cpu_to_le64(iova + unmapped - 1),
        };

        ret = viommu_add_req(vdomain->viommu, &unmap, sizeof(unmap));
        return ret ? 0 : unmapped;
}

static phys_addr_t viommu_iova_to_phys(struct iommu_domain *domain,
                                       dma_addr_t iova)
{
        u64 paddr = 0;
        unsigned long flags;
        struct viommu_mapping *mapping;
        struct interval_tree_node *node;
        struct viommu_domain *vdomain = to_viommu_domain(domain);

        spin_lock_irqsave(&vdomain->mappings_lock, flags);
        node = interval_tree_iter_first(&vdomain->mappings, iova, iova);
        if (node) {
                mapping = container_of(node, struct viommu_mapping, iova);
                paddr = mapping->paddr + (iova - mapping->iova.start);
        }
        spin_unlock_irqrestore(&vdomain->mappings_lock, flags);

        return paddr;
}

static void viommu_iotlb_sync(struct iommu_domain *domain,
                              struct iommu_iotlb_gather *gather)
{
        struct viommu_domain *vdomain = to_viommu_domain(domain);

        viommu_sync_req(vdomain->viommu);
}

static int viommu_iotlb_sync_map(struct iommu_domain *domain,
                                 unsigned long iova, size_t size)
{
        struct viommu_domain *vdomain = to_viommu_domain(domain);

        /*
         * May be called before the viommu is initialized including
         * while creating direct mapping
         */
        if (!vdomain->nr_endpoints)
                return 0;
        return viommu_sync_req(vdomain->viommu);
}

static void viommu_flush_iotlb_all(struct iommu_domain *domain)
{
        struct viommu_domain *vdomain = to_viommu_domain(domain);

        /*
         * May be called before the viommu is initialized including
         * while creating direct mapping
         */
        if (!vdomain->nr_endpoints)
                return;
        viommu_sync_req(vdomain->viommu);
}

static void viommu_get_resv_regions(struct device *dev, struct list_head *head)
{
        struct iommu_resv_region *entry, *new_entry, *msi = NULL;
        struct viommu_endpoint *vdev = dev_iommu_priv_get(dev);
        int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;

        list_for_each_entry(entry, &vdev->resv_regions, list) {
                if (entry->type == IOMMU_RESV_MSI)
                        msi = entry;

                new_entry = kmemdup(entry, sizeof(*entry), GFP_KERNEL);
                if (!new_entry)
                        return;
                list_add_tail(&new_entry->list, head);
        }

        /*
         * If the device didn't register any bypass MSI window, add a
         * software-mapped region.
         */
        if (!msi) {
                msi = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH,
                                              prot, IOMMU_RESV_SW_MSI,
                                              GFP_KERNEL);
                if (!msi)
                        return;

                list_add_tail(&msi->list, head);
        }

        iommu_dma_get_resv_regions(dev, head);
}

static const struct bus_type *virtio_bus_type;

static int viommu_match_node(struct device *dev, const void *data)
{
        return device_match_fwnode(dev->parent, data);
}

static struct viommu_dev *viommu_get_by_fwnode(struct fwnode_handle *fwnode)
{
        struct device *dev = bus_find_device(virtio_bus_type, NULL, fwnode,
                                             viommu_match_node);

        put_device(dev);

        return dev ? dev_to_virtio(dev)->priv : NULL;
}

static struct iommu_device *viommu_probe_device(struct device *dev)
{
        int ret;
        struct viommu_endpoint *vdev;
        struct viommu_dev *viommu = NULL;
        struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);

        viommu = viommu_get_by_fwnode(fwspec->iommu_fwnode);
        if (!viommu)
                return ERR_PTR(-ENODEV);

        vdev = kzalloc_obj(*vdev);
        if (!vdev)
                return ERR_PTR(-ENOMEM);

        vdev->dev = dev;
        vdev->viommu = viommu;
        INIT_LIST_HEAD(&vdev->resv_regions);
        dev_iommu_priv_set(dev, vdev);

        if (viommu->probe_size) {
                /* Get additional information for this endpoint */
                ret = viommu_probe_endpoint(viommu, dev);
                if (ret)
                        goto err_free_dev;
        }

        return &viommu->iommu;

err_free_dev:
        iommu_put_resv_regions(dev, &vdev->resv_regions);
        kfree(vdev);

        return ERR_PTR(ret);
}

static void viommu_release_device(struct device *dev)
{
        struct viommu_endpoint *vdev = dev_iommu_priv_get(dev);

        viommu_detach_dev(vdev);
        iommu_put_resv_regions(dev, &vdev->resv_regions);
        kfree(vdev);
}

static struct iommu_group *viommu_device_group(struct device *dev)
{
        if (dev_is_pci(dev))
                return pci_device_group(dev);
        else
                return generic_device_group(dev);
}

static int viommu_of_xlate(struct device *dev,
                           const struct of_phandle_args *args)
{
        return iommu_fwspec_add_ids(dev, args->args, 1);
}

static bool viommu_capable(struct device *dev, enum iommu_cap cap)
{
        switch (cap) {
        case IOMMU_CAP_CACHE_COHERENCY:
                return true;
        case IOMMU_CAP_DEFERRED_FLUSH:
                return true;
        default:
                return false;
        }
}

static const struct iommu_ops viommu_ops = {
        .capable                = viommu_capable,
        .domain_alloc_identity  = viommu_domain_alloc_identity,
        .domain_alloc_paging    = viommu_domain_alloc_paging,
        .probe_device           = viommu_probe_device,
        .release_device         = viommu_release_device,
        .device_group           = viommu_device_group,
        .get_resv_regions       = viommu_get_resv_regions,
        .of_xlate               = viommu_of_xlate,
        .owner                  = THIS_MODULE,
        .default_domain_ops = &(const struct iommu_domain_ops) {
                .attach_dev             = viommu_attach_dev,
                .map_pages              = viommu_map_pages,
                .unmap_pages            = viommu_unmap_pages,
                .iova_to_phys           = viommu_iova_to_phys,
                .flush_iotlb_all        = viommu_flush_iotlb_all,
                .iotlb_sync             = viommu_iotlb_sync,
                .iotlb_sync_map         = viommu_iotlb_sync_map,
                .free                   = viommu_domain_free,
        }
};

static int viommu_init_vqs(struct viommu_dev *viommu)
{
        struct virtio_device *vdev = dev_to_virtio(viommu->dev);
        struct virtqueue_info vqs_info[] = {
                { "request" },
                { "event", viommu_event_handler },
        };

        return virtio_find_vqs(vdev, VIOMMU_NR_VQS, viommu->vqs,
                               vqs_info, NULL);
}

static int viommu_fill_evtq(struct viommu_dev *viommu)
{
        int i, ret;
        struct scatterlist sg[1];
        struct viommu_event *evts;
        struct virtqueue *vq = viommu->vqs[VIOMMU_EVENT_VQ];
        size_t nr_evts = vq->num_free;

        viommu->evts = evts = devm_kmalloc_array(viommu->dev, nr_evts,
                                                 sizeof(*evts), GFP_KERNEL);
        if (!evts)
                return -ENOMEM;

        for (i = 0; i < nr_evts; i++) {
                sg_init_one(sg, &evts[i], sizeof(*evts));
                ret = virtqueue_add_inbuf(vq, sg, 1, &evts[i], GFP_KERNEL);
                if (ret)
                        return ret;
        }

        return 0;
}

static int viommu_probe(struct virtio_device *vdev)
{
        struct device *parent_dev = vdev->dev.parent;
        struct viommu_dev *viommu = NULL;
        struct device *dev = &vdev->dev;
        u64 input_start = 0;
        u64 input_end = -1UL;
        int ret;

        if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1) ||
            !virtio_has_feature(vdev, VIRTIO_IOMMU_F_MAP_UNMAP))
                return -ENODEV;

        viommu = devm_kzalloc(dev, sizeof(*viommu), GFP_KERNEL);
        if (!viommu)
                return -ENOMEM;

        /* Borrow this for easy lookups later */
        virtio_bus_type = dev->bus;

        spin_lock_init(&viommu->request_lock);
        ida_init(&viommu->domain_ids);
        viommu->dev = dev;
        viommu->vdev = vdev;
        INIT_LIST_HEAD(&viommu->requests);

        ret = viommu_init_vqs(viommu);
        if (ret)
                return ret;

        virtio_cread_le(vdev, struct virtio_iommu_config, page_size_mask,
                        &viommu->pgsize_bitmap);

        if (!viommu->pgsize_bitmap) {
                ret = -EINVAL;
                goto err_free_vqs;
        }

        viommu->map_flags = VIRTIO_IOMMU_MAP_F_READ | VIRTIO_IOMMU_MAP_F_WRITE;
        viommu->last_domain = ~0U;

        /* Optional features */
        virtio_cread_le_feature(vdev, VIRTIO_IOMMU_F_INPUT_RANGE,
                                struct virtio_iommu_config, input_range.start,
                                &input_start);

        virtio_cread_le_feature(vdev, VIRTIO_IOMMU_F_INPUT_RANGE,
                                struct virtio_iommu_config, input_range.end,
                                &input_end);

        virtio_cread_le_feature(vdev, VIRTIO_IOMMU_F_DOMAIN_RANGE,
                                struct virtio_iommu_config, domain_range.start,
                                &viommu->first_domain);

        virtio_cread_le_feature(vdev, VIRTIO_IOMMU_F_DOMAIN_RANGE,
                                struct virtio_iommu_config, domain_range.end,
                                &viommu->last_domain);

        virtio_cread_le_feature(vdev, VIRTIO_IOMMU_F_PROBE,
                                struct virtio_iommu_config, probe_size,
                                &viommu->probe_size);

        viommu->geometry = (struct iommu_domain_geometry) {
                .aperture_start = input_start,
                .aperture_end   = input_end,
                .force_aperture = true,
        };

        if (virtio_has_feature(vdev, VIRTIO_IOMMU_F_MMIO))
                viommu->map_flags |= VIRTIO_IOMMU_MAP_F_MMIO;

        /* Reserve an ID to use as the bypass domain */
        if (virtio_has_feature(viommu->vdev, VIRTIO_IOMMU_F_BYPASS_CONFIG)) {
                viommu->identity_domain_id = viommu->first_domain;
                viommu->first_domain++;
        }

        virtio_device_ready(vdev);

        /* Populate the event queue with buffers */
        ret = viommu_fill_evtq(viommu);
        if (ret)
                goto err_free_vqs;

        ret = iommu_device_sysfs_add(&viommu->iommu, dev, NULL, "%s",
                                     virtio_bus_name(vdev));
        if (ret)
                goto err_free_vqs;

        vdev->priv = viommu;

        iommu_device_register(&viommu->iommu, &viommu_ops, parent_dev);

        dev_info(dev, "input address: %u bits\n",
                 order_base_2(viommu->geometry.aperture_end));
        dev_info(dev, "page mask: %#llx\n", viommu->pgsize_bitmap);

        return 0;

err_free_vqs:
        vdev->config->del_vqs(vdev);

        return ret;
}

static void viommu_remove(struct virtio_device *vdev)
{
        struct viommu_dev *viommu = vdev->priv;

        iommu_device_sysfs_remove(&viommu->iommu);
        iommu_device_unregister(&viommu->iommu);

        /* Stop all virtqueues */
        virtio_reset_device(vdev);
        vdev->config->del_vqs(vdev);

        dev_info(&vdev->dev, "device removed\n");
}

static void viommu_config_changed(struct virtio_device *vdev)
{
        dev_warn(&vdev->dev, "config changed\n");
}

static unsigned int features[] = {
        VIRTIO_IOMMU_F_MAP_UNMAP,
        VIRTIO_IOMMU_F_INPUT_RANGE,
        VIRTIO_IOMMU_F_DOMAIN_RANGE,
        VIRTIO_IOMMU_F_PROBE,
        VIRTIO_IOMMU_F_MMIO,
        VIRTIO_IOMMU_F_BYPASS_CONFIG,
};

static struct virtio_device_id id_table[] = {
        { VIRTIO_ID_IOMMU, VIRTIO_DEV_ANY_ID },
        { 0 },
};
MODULE_DEVICE_TABLE(virtio, id_table);

static struct virtio_driver virtio_iommu_drv = {
        .driver.name            = KBUILD_MODNAME,
        .id_table               = id_table,
        .feature_table          = features,
        .feature_table_size     = ARRAY_SIZE(features),
        .probe                  = viommu_probe,
        .remove                 = viommu_remove,
        .config_changed         = viommu_config_changed,
};

module_virtio_driver(virtio_iommu_drv);

MODULE_DESCRIPTION("Virtio IOMMU driver");
MODULE_AUTHOR("Jean-Philippe Brucker <jean-philippe.brucker@arm.com>");
MODULE_LICENSE("GPL v2");