/*
 * VFIO-KVM bridge pseudo device
 *
 * Copyright (C) 2013 Red Hat, Inc.  All rights reserved.
 *     Author: Alex Williamson <alex.williamson@redhat.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/errno.h>
#include <linux/file.h>
#include <linux/kvm_host.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/vfio.h>

struct kvm_vfio_group {
        struct list_head node;
        struct vfio_group *vfio_group;
};

struct kvm_vfio {
        struct list_head group_list;
        struct mutex lock;
        bool noncoherent;
};

static struct vfio_group *kvm_vfio_group_get_external_user(struct file *filep)
{
        struct vfio_group *vfio_group;
        struct vfio_group *(*fn)(struct file *);

        fn = symbol_get(vfio_group_get_external_user);
        if (!fn)
                return ERR_PTR(-EINVAL);

        vfio_group = fn(filep);

        symbol_put(vfio_group_get_external_user);

        return vfio_group;
}

static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group)
{
        void (*fn)(struct vfio_group *);

        fn = symbol_get(vfio_group_put_external_user);
        if (!fn)
                return;

        fn(vfio_group);

        symbol_put(vfio_group_put_external_user);
}

/*
 * Groups can use the same or different IOMMU domains.  If the same then
 * adding a new group may change the coherency of groups we've previously
 * been told about.  We don't want to care about any of that so we retest
 * each group and bail as soon as we find one that's noncoherent.  This
 * means we only ever [un]register_noncoherent_dma once for the whole device.
 */
static void kvm_vfio_update_coherency(struct kvm_device *dev)
{
        struct kvm_vfio *kv = dev->private;
        bool noncoherent = false;
        struct kvm_vfio_group *kvg;

        mutex_lock(&kv->lock);

        list_for_each_entry(kvg, &kv->group_list, node) {
                /*
                 * TODO: We need an interface to check the coherency of
                 * the IOMMU domain this group is using.  For now, assume
                 * it's always noncoherent.
                 */
                noncoherent = true;
                break;
        }

        if (noncoherent != kv->noncoherent) {
                kv->noncoherent = noncoherent;

                if (kv->noncoherent)
                        kvm_arch_register_noncoherent_dma(dev->kvm);
                else
                        kvm_arch_unregister_noncoherent_dma(dev->kvm);
        }

        mutex_unlock(&kv->lock);
}

static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
{
        struct kvm_vfio *kv = dev->private;
        struct vfio_group *vfio_group;
        struct kvm_vfio_group *kvg;
        int32_t __user *argp = (int32_t __user *)(unsigned long)arg;
        struct fd f;
        int32_t fd;
        int ret;

        switch (attr) {
        case KVM_DEV_VFIO_GROUP_ADD:
                if (get_user(fd, argp))
                        return -EFAULT;

                f = fdget(fd);
                if (!f.file)
                        return -EBADF;

                vfio_group = kvm_vfio_group_get_external_user(f.file);
                fdput(f);

                if (IS_ERR(vfio_group))
                        return PTR_ERR(vfio_group);

                mutex_lock(&kv->lock);

                list_for_each_entry(kvg, &kv->group_list, node) {
                        if (kvg->vfio_group == vfio_group) {
                                mutex_unlock(&kv->lock);
                                kvm_vfio_group_put_external_user(vfio_group);
                                return -EEXIST;
                        }
                }

                kvg = kzalloc(sizeof(*kvg), GFP_KERNEL);
                if (!kvg) {
                        mutex_unlock(&kv->lock);
                        kvm_vfio_group_put_external_user(vfio_group);
                        return -ENOMEM;
                }

                list_add_tail(&kvg->node, &kv->group_list);
                kvg->vfio_group = vfio_group;

                mutex_unlock(&kv->lock);

                kvm_vfio_update_coherency(dev);

                return 0;

        case KVM_DEV_VFIO_GROUP_DEL:
                if (get_user(fd, argp))
                        return -EFAULT;

                f = fdget(fd);
                if (!f.file)
                        return -EBADF;

                vfio_group = kvm_vfio_group_get_external_user(f.file);
                fdput(f);

                if (IS_ERR(vfio_group))
                        return PTR_ERR(vfio_group);

                ret = -ENOENT;

                mutex_lock(&kv->lock);

                list_for_each_entry(kvg, &kv->group_list, node) {
                        if (kvg->vfio_group != vfio_group)
                                continue;

                        list_del(&kvg->node);
                        kvm_vfio_group_put_external_user(kvg->vfio_group);
                        kfree(kvg);
                        ret = 0;
                        break;
                }

                mutex_unlock(&kv->lock);

                kvm_vfio_group_put_external_user(vfio_group);

                kvm_vfio_update_coherency(dev);

                return ret;
        }

        return -ENXIO;
}

static int kvm_vfio_set_attr(struct kvm_device *dev,
                             struct kvm_device_attr *attr)
{
        switch (attr->group) {
        case KVM_DEV_VFIO_GROUP:
                return kvm_vfio_set_group(dev, attr->attr, attr->addr);
        }

        return -ENXIO;
}

static int kvm_vfio_has_attr(struct kvm_device *dev,
                             struct kvm_device_attr *attr)
{
        switch (attr->group) {
        case KVM_DEV_VFIO_GROUP:
                switch (attr->attr) {
                case KVM_DEV_VFIO_GROUP_ADD:
                case KVM_DEV_VFIO_GROUP_DEL:
                        return 0;
                }

                break;
        }

        return -ENXIO;
}

static void kvm_vfio_destroy(struct kvm_device *dev)
{
        struct kvm_vfio *kv = dev->private;
        struct kvm_vfio_group *kvg, *tmp;

        list_for_each_entry_safe(kvg, tmp, &kv->group_list, node) {
                kvm_vfio_group_put_external_user(kvg->vfio_group);
                list_del(&kvg->node);
                kfree(kvg);
        }

        kvm_vfio_update_coherency(dev);

        kfree(kv);
        kfree(dev); /* alloc by kvm_ioctl_create_device, free by .destroy */
}

static int kvm_vfio_create(struct kvm_device *dev, u32 type)
{
        struct kvm_device *tmp;
        struct kvm_vfio *kv;

        /* Only one VFIO "device" per VM */
        list_for_each_entry(tmp, &dev->kvm->devices, vm_node)
                if (tmp->ops == &kvm_vfio_ops)
                        return -EBUSY;

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

        INIT_LIST_HEAD(&kv->group_list);
        mutex_init(&kv->lock);

        dev->private = kv;

        return 0;
}

struct kvm_device_ops kvm_vfio_ops = {
        .name = "kvm-vfio",
        .create = kvm_vfio_create,
        .destroy = kvm_vfio_destroy,
        .set_attr = kvm_vfio_set_attr,
        .has_attr = kvm_vfio_has_attr,
};