// SPDX-License-Identifier: GPL-2.0

/*
 * Xen dma-buf functionality for gntdev.
 *
 * DMA buffer implementation is based on drivers/gpu/drm/drm_prime.c.
 *
 * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/dma-buf.h>
#include <linux/dma-direct.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include <linux/module.h>

#include <xen/xen.h>
#include <xen/grant_table.h>

#include "gntdev-common.h"
#include "gntdev-dmabuf.h"

MODULE_IMPORT_NS("DMA_BUF");

struct gntdev_dmabuf {
        struct gntdev_dmabuf_priv *priv;
        struct dma_buf *dmabuf;
        struct list_head next;
        int fd;

        union {
                struct {
                        /* Exported buffers are reference counted. */
                        struct kref refcount;

                        struct gntdev_priv *priv;
                        struct gntdev_grant_map *map;
                } exp;
                struct {
                        /* Granted references of the imported buffer. */
                        grant_ref_t *refs;
                        /* Scatter-gather table of the imported buffer. */
                        struct sg_table *sgt;
                        /* dma-buf attachment of the imported buffer. */
                        struct dma_buf_attachment *attach;
                } imp;
        } u;

        /* Number of pages this buffer has. */
        int nr_pages;
        /* Pages of this buffer (only for dma-buf export). */
        struct page **pages;
};

struct gntdev_dmabuf_wait_obj {
        struct list_head next;
        struct gntdev_dmabuf *gntdev_dmabuf;
        struct completion completion;
};

struct gntdev_dmabuf_attachment {
        struct sg_table *sgt;
        enum dma_data_direction dir;
};

struct gntdev_dmabuf_priv {
        /* List of exported DMA buffers. */
        struct list_head exp_list;
        /* List of wait objects. */
        struct list_head exp_wait_list;
        /* List of imported DMA buffers. */
        struct list_head imp_list;
        /* This is the lock which protects dma_buf_xxx lists. */
        struct mutex lock;
        /*
         * We reference this file while exporting dma-bufs, so
         * the grant device context is not destroyed while there are
         * external users alive.
         */
        struct file *filp;
};

/* DMA buffer export support. */

/* Implementation of wait for exported DMA buffer to be released. */

static void dmabuf_exp_release(struct kref *kref);

static struct gntdev_dmabuf_wait_obj *
dmabuf_exp_wait_obj_new(struct gntdev_dmabuf_priv *priv,
                        struct gntdev_dmabuf *gntdev_dmabuf)
{
        struct gntdev_dmabuf_wait_obj *obj;

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

        init_completion(&obj->completion);
        obj->gntdev_dmabuf = gntdev_dmabuf;

        mutex_lock(&priv->lock);
        list_add(&obj->next, &priv->exp_wait_list);
        /* Put our reference and wait for gntdev_dmabuf's release to fire. */
        kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release);
        mutex_unlock(&priv->lock);
        return obj;
}

static void dmabuf_exp_wait_obj_free(struct gntdev_dmabuf_priv *priv,
                                     struct gntdev_dmabuf_wait_obj *obj)
{
        mutex_lock(&priv->lock);
        list_del(&obj->next);
        mutex_unlock(&priv->lock);
        kfree(obj);
}

static int dmabuf_exp_wait_obj_wait(struct gntdev_dmabuf_wait_obj *obj,
                                    u32 wait_to_ms)
{
        if (wait_for_completion_timeout(&obj->completion,
                        msecs_to_jiffies(wait_to_ms)) <= 0)
                return -ETIMEDOUT;

        return 0;
}

static void dmabuf_exp_wait_obj_signal(struct gntdev_dmabuf_priv *priv,
                                       struct gntdev_dmabuf *gntdev_dmabuf)
{
        struct gntdev_dmabuf_wait_obj *obj;

        list_for_each_entry(obj, &priv->exp_wait_list, next)
                if (obj->gntdev_dmabuf == gntdev_dmabuf) {
                        pr_debug("Found gntdev_dmabuf in the wait list, wake\n");
                        complete_all(&obj->completion);
                        break;
                }
}

static struct gntdev_dmabuf *
dmabuf_exp_wait_obj_get_dmabuf(struct gntdev_dmabuf_priv *priv, int fd)
{
        struct gntdev_dmabuf *gntdev_dmabuf, *ret = ERR_PTR(-ENOENT);

        mutex_lock(&priv->lock);
        list_for_each_entry(gntdev_dmabuf, &priv->exp_list, next)
                if (gntdev_dmabuf->fd == fd) {
                        pr_debug("Found gntdev_dmabuf in the wait list\n");
                        kref_get(&gntdev_dmabuf->u.exp.refcount);
                        ret = gntdev_dmabuf;
                        break;
                }
        mutex_unlock(&priv->lock);
        return ret;
}

static int dmabuf_exp_wait_released(struct gntdev_dmabuf_priv *priv, int fd,
                                    int wait_to_ms)
{
        struct gntdev_dmabuf *gntdev_dmabuf;
        struct gntdev_dmabuf_wait_obj *obj;
        int ret;

        pr_debug("Will wait for dma-buf with fd %d\n", fd);
        /*
         * Try to find the DMA buffer: if not found means that
         * either the buffer has already been released or file descriptor
         * provided is wrong.
         */
        gntdev_dmabuf = dmabuf_exp_wait_obj_get_dmabuf(priv, fd);
        if (IS_ERR(gntdev_dmabuf))
                return PTR_ERR(gntdev_dmabuf);

        /*
         * gntdev_dmabuf still exists and is reference count locked by us now,
         * so prepare to wait: allocate wait object and add it to the wait list,
         * so we can find it on release.
         */
        obj = dmabuf_exp_wait_obj_new(priv, gntdev_dmabuf);
        if (IS_ERR(obj))
                return PTR_ERR(obj);

        ret = dmabuf_exp_wait_obj_wait(obj, wait_to_ms);
        dmabuf_exp_wait_obj_free(priv, obj);
        return ret;
}

/* DMA buffer export support. */

static struct sg_table *
dmabuf_pages_to_sgt(struct page **pages, unsigned int nr_pages)
{
        struct sg_table *sgt;
        int ret;

        sgt = kmalloc_obj(*sgt);
        if (!sgt) {
                ret = -ENOMEM;
                goto out;
        }

        ret = sg_alloc_table_from_pages(sgt, pages, nr_pages, 0,
                                        nr_pages << PAGE_SHIFT,
                                        GFP_KERNEL);
        if (ret)
                goto out;

        return sgt;

out:
        kfree(sgt);
        return ERR_PTR(ret);
}

static int dmabuf_exp_ops_attach(struct dma_buf *dma_buf,
                                 struct dma_buf_attachment *attach)
{
        struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach;

        gntdev_dmabuf_attach = kzalloc_obj(*gntdev_dmabuf_attach);
        if (!gntdev_dmabuf_attach)
                return -ENOMEM;

        gntdev_dmabuf_attach->dir = DMA_NONE;
        attach->priv = gntdev_dmabuf_attach;
        return 0;
}

static void dmabuf_exp_ops_detach(struct dma_buf *dma_buf,
                                  struct dma_buf_attachment *attach)
{
        struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv;

        if (gntdev_dmabuf_attach) {
                struct sg_table *sgt = gntdev_dmabuf_attach->sgt;

                if (sgt) {
                        if (gntdev_dmabuf_attach->dir != DMA_NONE)
                                dma_unmap_sgtable(attach->dev, sgt,
                                                  gntdev_dmabuf_attach->dir,
                                                  DMA_ATTR_SKIP_CPU_SYNC);
                        sg_free_table(sgt);
                }

                kfree(sgt);
                kfree(gntdev_dmabuf_attach);
                attach->priv = NULL;
        }
}

static struct sg_table *
dmabuf_exp_ops_map_dma_buf(struct dma_buf_attachment *attach,
                           enum dma_data_direction dir)
{
        struct gntdev_dmabuf_attachment *gntdev_dmabuf_attach = attach->priv;
        struct gntdev_dmabuf *gntdev_dmabuf = attach->dmabuf->priv;
        struct sg_table *sgt;

        pr_debug("Mapping %d pages for dev %p\n", gntdev_dmabuf->nr_pages,
                 attach->dev);

        if (dir == DMA_NONE || !gntdev_dmabuf_attach)
                return ERR_PTR(-EINVAL);

        /* Return the cached mapping when possible. */
        if (gntdev_dmabuf_attach->dir == dir)
                return gntdev_dmabuf_attach->sgt;

        /*
         * Two mappings with different directions for the same attachment are
         * not allowed.
         */
        if (gntdev_dmabuf_attach->dir != DMA_NONE)
                return ERR_PTR(-EBUSY);

        sgt = dmabuf_pages_to_sgt(gntdev_dmabuf->pages,
                                  gntdev_dmabuf->nr_pages);
        if (!IS_ERR(sgt)) {
                if (dma_map_sgtable(attach->dev, sgt, dir,
                                    DMA_ATTR_SKIP_CPU_SYNC)) {
                        sg_free_table(sgt);
                        kfree(sgt);
                        sgt = ERR_PTR(-ENOMEM);
                } else {
                        gntdev_dmabuf_attach->sgt = sgt;
                        gntdev_dmabuf_attach->dir = dir;
                }
        }
        if (IS_ERR(sgt))
                pr_debug("Failed to map sg table for dev %p\n", attach->dev);
        return sgt;
}

static void dmabuf_exp_ops_unmap_dma_buf(struct dma_buf_attachment *attach,
                                         struct sg_table *sgt,
                                         enum dma_data_direction dir)
{
        /* Not implemented. The unmap is done at dmabuf_exp_ops_detach(). */
}

static void dmabuf_exp_release(struct kref *kref)
{
        struct gntdev_dmabuf *gntdev_dmabuf =
                container_of(kref, struct gntdev_dmabuf, u.exp.refcount);

        dmabuf_exp_wait_obj_signal(gntdev_dmabuf->priv, gntdev_dmabuf);
        list_del(&gntdev_dmabuf->next);
        fput(gntdev_dmabuf->priv->filp);
        kfree(gntdev_dmabuf);
}

static void dmabuf_exp_remove_map(struct gntdev_priv *priv,
                                  struct gntdev_grant_map *map)
{
        mutex_lock(&priv->lock);
        list_del(&map->next);
        gntdev_put_map(NULL /* already removed */, map);
        mutex_unlock(&priv->lock);
}

static void dmabuf_exp_ops_release(struct dma_buf *dma_buf)
{
        struct gntdev_dmabuf *gntdev_dmabuf = dma_buf->priv;
        struct gntdev_dmabuf_priv *priv = gntdev_dmabuf->priv;

        dmabuf_exp_remove_map(gntdev_dmabuf->u.exp.priv,
                              gntdev_dmabuf->u.exp.map);
        mutex_lock(&priv->lock);
        kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release);
        mutex_unlock(&priv->lock);
}

static const struct dma_buf_ops dmabuf_exp_ops =  {
        .attach = dmabuf_exp_ops_attach,
        .detach = dmabuf_exp_ops_detach,
        .map_dma_buf = dmabuf_exp_ops_map_dma_buf,
        .unmap_dma_buf = dmabuf_exp_ops_unmap_dma_buf,
        .release = dmabuf_exp_ops_release,
};

struct gntdev_dmabuf_export_args {
        struct gntdev_priv *priv;
        struct gntdev_grant_map *map;
        struct gntdev_dmabuf_priv *dmabuf_priv;
        struct device *dev;
        int count;
        struct page **pages;
        u32 fd;
};

static int dmabuf_exp_from_pages(struct gntdev_dmabuf_export_args *args)
{
        DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
        struct gntdev_dmabuf *gntdev_dmabuf __free(kfree) = NULL;
        CLASS(get_unused_fd, ret)(O_CLOEXEC);

        if (ret < 0)
                return ret;

        gntdev_dmabuf = kzalloc_obj(*gntdev_dmabuf);
        if (!gntdev_dmabuf)
                return -ENOMEM;

        kref_init(&gntdev_dmabuf->u.exp.refcount);

        gntdev_dmabuf->priv = args->dmabuf_priv;
        gntdev_dmabuf->nr_pages = args->count;
        gntdev_dmabuf->pages = args->pages;
        gntdev_dmabuf->u.exp.priv = args->priv;
        gntdev_dmabuf->u.exp.map = args->map;

        exp_info.exp_name = KBUILD_MODNAME;
        if (args->dev->driver && args->dev->driver->owner)
                exp_info.owner = args->dev->driver->owner;
        else
                exp_info.owner = THIS_MODULE;
        exp_info.ops = &dmabuf_exp_ops;
        exp_info.size = args->count << PAGE_SHIFT;
        exp_info.flags = O_RDWR;
        exp_info.priv = gntdev_dmabuf;

        gntdev_dmabuf->dmabuf = dma_buf_export(&exp_info);
        if (IS_ERR(gntdev_dmabuf->dmabuf))
                return PTR_ERR(gntdev_dmabuf->dmabuf);

        gntdev_dmabuf->fd = ret;
        args->fd = ret;

        pr_debug("Exporting DMA buffer with fd %d\n", ret);

        get_file(gntdev_dmabuf->priv->filp);
        mutex_lock(&args->dmabuf_priv->lock);
        list_add(&gntdev_dmabuf->next, &args->dmabuf_priv->exp_list);
        mutex_unlock(&args->dmabuf_priv->lock);

        fd_install(take_fd(ret), no_free_ptr(gntdev_dmabuf)->dmabuf->file);
        return 0;
}

static struct gntdev_grant_map *
dmabuf_exp_alloc_backing_storage(struct gntdev_priv *priv, int dmabuf_flags,
                                 int count)
{
        struct gntdev_grant_map *map;

        if (unlikely(gntdev_test_page_count(count)))
                return ERR_PTR(-EINVAL);

        if ((dmabuf_flags & GNTDEV_DMA_FLAG_WC) &&
            (dmabuf_flags & GNTDEV_DMA_FLAG_COHERENT)) {
                pr_debug("Wrong dma-buf flags: 0x%x\n", dmabuf_flags);
                return ERR_PTR(-EINVAL);
        }

        map = gntdev_alloc_map(priv, count, dmabuf_flags);
        if (!map)
                return ERR_PTR(-ENOMEM);

        return map;
}

static int dmabuf_exp_from_refs(struct gntdev_priv *priv, int flags,
                                int count, u32 domid, u32 *refs, u32 *fd)
{
        struct gntdev_grant_map *map;
        struct gntdev_dmabuf_export_args args;
        int i, ret;

        map = dmabuf_exp_alloc_backing_storage(priv, flags, count);
        if (IS_ERR(map))
                return PTR_ERR(map);

        for (i = 0; i < count; i++) {
                map->grants[i].domid = domid;
                map->grants[i].ref = refs[i];
        }

        mutex_lock(&priv->lock);
        gntdev_add_map(priv, map);
        mutex_unlock(&priv->lock);

        map->flags |= GNTMAP_host_map;
#if defined(CONFIG_X86)
        map->flags |= GNTMAP_device_map;
#endif

        ret = gntdev_map_grant_pages(map);
        if (ret < 0)
                goto out;

        args.priv = priv;
        args.map = map;
        args.dev = priv->dma_dev;
        args.dmabuf_priv = priv->dmabuf_priv;
        args.count = map->count;
        args.pages = map->pages;
        args.fd = -1; /* Shut up unnecessary gcc warning for i386 */

        ret = dmabuf_exp_from_pages(&args);
        if (ret < 0)
                goto out;

        *fd = args.fd;
        return 0;

out:
        dmabuf_exp_remove_map(priv, map);
        return ret;
}

/* DMA buffer import support. */

static int
dmabuf_imp_grant_foreign_access(unsigned long *gfns, u32 *refs,
                                int count, int domid)
{
        grant_ref_t priv_gref_head;
        int i, ret;

        ret = gnttab_alloc_grant_references(count, &priv_gref_head);
        if (ret < 0) {
                pr_debug("Cannot allocate grant references, ret %d\n", ret);
                return ret;
        }

        for (i = 0; i < count; i++) {
                int cur_ref;

                cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
                if (cur_ref < 0) {
                        ret = cur_ref;
                        pr_debug("Cannot claim grant reference, ret %d\n", ret);
                        goto out;
                }

                gnttab_grant_foreign_access_ref(cur_ref, domid,
                                                gfns[i], 0);
                refs[i] = cur_ref;
        }

        return 0;

out:
        gnttab_free_grant_references(priv_gref_head);
        return ret;
}

static void dmabuf_imp_end_foreign_access(u32 *refs, int count)
{
        int i;

        for (i = 0; i < count; i++)
                if (refs[i] != INVALID_GRANT_REF)
                        gnttab_end_foreign_access(refs[i], NULL);
}

static void dmabuf_imp_free_storage(struct gntdev_dmabuf *gntdev_dmabuf)
{
        kfree(gntdev_dmabuf->u.imp.refs);
        kfree(gntdev_dmabuf);
}

static struct gntdev_dmabuf *dmabuf_imp_alloc_storage(int count)
{
        struct gntdev_dmabuf *gntdev_dmabuf;
        int i;

        gntdev_dmabuf = kzalloc_obj(*gntdev_dmabuf);
        if (!gntdev_dmabuf)
                goto fail_no_free;

        gntdev_dmabuf->u.imp.refs = kzalloc_objs(gntdev_dmabuf->u.imp.refs[0],
                                                 count);
        if (!gntdev_dmabuf->u.imp.refs)
                goto fail;

        gntdev_dmabuf->nr_pages = count;

        for (i = 0; i < count; i++)
                gntdev_dmabuf->u.imp.refs[i] = INVALID_GRANT_REF;

        return gntdev_dmabuf;

fail:
        dmabuf_imp_free_storage(gntdev_dmabuf);
fail_no_free:
        return ERR_PTR(-ENOMEM);
}

static struct gntdev_dmabuf *
dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
                   int fd, int count, int domid)
{
        struct gntdev_dmabuf *gntdev_dmabuf, *ret;
        struct dma_buf *dma_buf;
        struct dma_buf_attachment *attach;
        struct sg_table *sgt;
        struct sg_dma_page_iter sg_iter;
        unsigned long *gfns;
        int i;

        dma_buf = dma_buf_get(fd);
        if (IS_ERR(dma_buf))
                return ERR_CAST(dma_buf);

        gntdev_dmabuf = dmabuf_imp_alloc_storage(count);
        if (IS_ERR(gntdev_dmabuf)) {
                ret = gntdev_dmabuf;
                goto fail_put;
        }

        gntdev_dmabuf->priv = priv;
        gntdev_dmabuf->fd = fd;

        attach = dma_buf_attach(dma_buf, dev);
        if (IS_ERR(attach)) {
                ret = ERR_CAST(attach);
                goto fail_free_obj;
        }

        gntdev_dmabuf->u.imp.attach = attach;

        sgt = dma_buf_map_attachment_unlocked(attach, DMA_BIDIRECTIONAL);
        if (IS_ERR(sgt)) {
                ret = ERR_CAST(sgt);
                goto fail_detach;
        }

        /* Check that we have zero offset. */
        if (sgt->sgl->offset) {
                ret = ERR_PTR(-EINVAL);
                pr_debug("DMA buffer has %d bytes offset, user-space expects 0\n",
                         sgt->sgl->offset);
                goto fail_unmap;
        }

        /* Check number of pages that imported buffer has. */
        if (attach->dmabuf->size != gntdev_dmabuf->nr_pages << PAGE_SHIFT) {
                ret = ERR_PTR(-EINVAL);
                pr_debug("DMA buffer has %zu pages, user-space expects %d\n",
                         attach->dmabuf->size, gntdev_dmabuf->nr_pages);
                goto fail_unmap;
        }

        gntdev_dmabuf->u.imp.sgt = sgt;

        gfns = kcalloc(count, sizeof(*gfns), GFP_KERNEL);
        if (!gfns) {
                ret = ERR_PTR(-ENOMEM);
                goto fail_unmap;
        }

        /*
         * Now convert sgt to array of gfns without accessing underlying pages.
         * It is not allowed to access the underlying struct page of an sg table
         * exported by DMA-buf, but since we deal with special Xen dma device here
         * (not a normal physical one) look at the dma addresses in the sg table
         * and then calculate gfns directly from them.
         */
        i = 0;
        for_each_sgtable_dma_page(sgt, &sg_iter, 0) {
                dma_addr_t addr = sg_page_iter_dma_address(&sg_iter);
                unsigned long pfn = bfn_to_pfn(XEN_PFN_DOWN(dma_to_phys(dev, addr)));

                gfns[i++] = pfn_to_gfn(pfn);
        }

        ret = ERR_PTR(dmabuf_imp_grant_foreign_access(gfns,
                                                      gntdev_dmabuf->u.imp.refs,
                                                      count, domid));
        kfree(gfns);
        if (IS_ERR(ret))
                goto fail_end_access;

        pr_debug("Imported DMA buffer with fd %d\n", fd);

        mutex_lock(&priv->lock);
        list_add(&gntdev_dmabuf->next, &priv->imp_list);
        mutex_unlock(&priv->lock);

        return gntdev_dmabuf;

fail_end_access:
        dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs, count);
fail_unmap:
        dma_buf_unmap_attachment_unlocked(attach, sgt, DMA_BIDIRECTIONAL);
fail_detach:
        dma_buf_detach(dma_buf, attach);
fail_free_obj:
        dmabuf_imp_free_storage(gntdev_dmabuf);
fail_put:
        dma_buf_put(dma_buf);
        return ret;
}

/*
 * Find the hyper dma-buf by its file descriptor and remove
 * it from the buffer's list.
 */
static struct gntdev_dmabuf *
dmabuf_imp_find_unlink(struct gntdev_dmabuf_priv *priv, int fd)
{
        struct gntdev_dmabuf *q, *gntdev_dmabuf, *ret = ERR_PTR(-ENOENT);

        mutex_lock(&priv->lock);
        list_for_each_entry_safe(gntdev_dmabuf, q, &priv->imp_list, next) {
                if (gntdev_dmabuf->fd == fd) {
                        pr_debug("Found gntdev_dmabuf in the import list\n");
                        ret = gntdev_dmabuf;
                        list_del(&gntdev_dmabuf->next);
                        break;
                }
        }
        mutex_unlock(&priv->lock);
        return ret;
}

static int dmabuf_imp_release(struct gntdev_dmabuf_priv *priv, u32 fd)
{
        struct gntdev_dmabuf *gntdev_dmabuf;
        struct dma_buf_attachment *attach;
        struct dma_buf *dma_buf;

        gntdev_dmabuf = dmabuf_imp_find_unlink(priv, fd);
        if (IS_ERR(gntdev_dmabuf))
                return PTR_ERR(gntdev_dmabuf);

        pr_debug("Releasing DMA buffer with fd %d\n", fd);

        dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs,
                                      gntdev_dmabuf->nr_pages);

        attach = gntdev_dmabuf->u.imp.attach;

        if (gntdev_dmabuf->u.imp.sgt)
                dma_buf_unmap_attachment_unlocked(attach, gntdev_dmabuf->u.imp.sgt,
                                                  DMA_BIDIRECTIONAL);
        dma_buf = attach->dmabuf;
        dma_buf_detach(attach->dmabuf, attach);
        dma_buf_put(dma_buf);

        dmabuf_imp_free_storage(gntdev_dmabuf);
        return 0;
}

static void dmabuf_imp_release_all(struct gntdev_dmabuf_priv *priv)
{
        struct gntdev_dmabuf *q, *gntdev_dmabuf;

        list_for_each_entry_safe(gntdev_dmabuf, q, &priv->imp_list, next)
                dmabuf_imp_release(priv, gntdev_dmabuf->fd);
}

/* DMA buffer IOCTL support. */

long gntdev_ioctl_dmabuf_exp_from_refs(struct gntdev_priv *priv,
                                       struct ioctl_gntdev_dmabuf_exp_from_refs __user *u)
{
        struct ioctl_gntdev_dmabuf_exp_from_refs op;
        u32 *refs;
        long ret;

        if (xen_pv_domain()) {
                pr_debug("Cannot provide dma-buf in a PV domain\n");
                return -EINVAL;
        }

        if (copy_from_user(&op, u, sizeof(op)) != 0)
                return -EFAULT;

        if (unlikely(gntdev_test_page_count(op.count)))
                return -EINVAL;

        refs = kcalloc(op.count, sizeof(*refs), GFP_KERNEL);
        if (!refs)
                return -ENOMEM;

        if (copy_from_user(refs, u->refs, sizeof(*refs) * op.count) != 0) {
                ret = -EFAULT;
                goto out;
        }

        ret = dmabuf_exp_from_refs(priv, op.flags, op.count,
                                   op.domid, refs, &op.fd);
        if (ret)
                goto out;

        if (copy_to_user(u, &op, sizeof(op)) != 0)
                ret = -EFAULT;

out:
        kfree(refs);
        return ret;
}

long gntdev_ioctl_dmabuf_exp_wait_released(struct gntdev_priv *priv,
                                           struct ioctl_gntdev_dmabuf_exp_wait_released __user *u)
{
        struct ioctl_gntdev_dmabuf_exp_wait_released op;

        if (copy_from_user(&op, u, sizeof(op)) != 0)
                return -EFAULT;

        return dmabuf_exp_wait_released(priv->dmabuf_priv, op.fd,
                                        op.wait_to_ms);
}

long gntdev_ioctl_dmabuf_imp_to_refs(struct gntdev_priv *priv,
                                     struct ioctl_gntdev_dmabuf_imp_to_refs __user *u)
{
        struct ioctl_gntdev_dmabuf_imp_to_refs op;
        struct gntdev_dmabuf *gntdev_dmabuf;
        long ret;

        if (copy_from_user(&op, u, sizeof(op)) != 0)
                return -EFAULT;

        if (unlikely(gntdev_test_page_count(op.count)))
                return -EINVAL;

        gntdev_dmabuf = dmabuf_imp_to_refs(priv->dmabuf_priv,
                                           priv->dma_dev, op.fd,
                                           op.count, op.domid);
        if (IS_ERR(gntdev_dmabuf))
                return PTR_ERR(gntdev_dmabuf);

        if (copy_to_user(u->refs, gntdev_dmabuf->u.imp.refs,
                         sizeof(*u->refs) * op.count) != 0) {
                ret = -EFAULT;
                goto out_release;
        }
        return 0;

out_release:
        dmabuf_imp_release(priv->dmabuf_priv, op.fd);
        return ret;
}

long gntdev_ioctl_dmabuf_imp_release(struct gntdev_priv *priv,
                                     struct ioctl_gntdev_dmabuf_imp_release __user *u)
{
        struct ioctl_gntdev_dmabuf_imp_release op;

        if (copy_from_user(&op, u, sizeof(op)) != 0)
                return -EFAULT;

        return dmabuf_imp_release(priv->dmabuf_priv, op.fd);
}

struct gntdev_dmabuf_priv *gntdev_dmabuf_init(struct file *filp)
{
        struct gntdev_dmabuf_priv *priv;

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

        mutex_init(&priv->lock);
        INIT_LIST_HEAD(&priv->exp_list);
        INIT_LIST_HEAD(&priv->exp_wait_list);
        INIT_LIST_HEAD(&priv->imp_list);

        priv->filp = filp;

        return priv;
}

void gntdev_dmabuf_fini(struct gntdev_dmabuf_priv *priv)
{
        dmabuf_imp_release_all(priv);
        kfree(priv);
}