/*
 * Copyright 2014 Advanced Micro Devices, Inc.
 * All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sub license, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
 */
/*
 * Authors:
 *    Christian König <christian.koenig@amd.com>
 */

/**
 * DOC: MMU Notifier
 *
 * For coherent userptr handling registers an MMU notifier to inform the driver
 * about updates on the page tables of a process.
 *
 * When somebody tries to invalidate the page tables we block the update until
 * all operations on the pages in question are completed, then those pages are
 * marked as accessed and also dirty if it wasn't a read only access.
 *
 * New command submissions using the userptrs in question are delayed until all
 * page table invalidation are completed and we once more see a coherent process
 * address space.
 */

#include <linux/firmware.h>
#include <linux/module.h>
#include <linux/mmu_notifier.h>
#include <linux/interval_tree.h>
#include <drm/drmP.h>
#include <drm/drm.h>

#include "amdgpu.h"
#include "amdgpu_amdkfd.h"

/**
 * struct amdgpu_mn
 *
 * @adev: amdgpu device pointer
 * @mm: process address space
 * @mn: MMU notifier structure
 * @type: type of MMU notifier
 * @work: destruction work item
 * @node: hash table node to find structure by adev and mn
 * @lock: rw semaphore protecting the notifier nodes
 * @objects: interval tree containing amdgpu_mn_nodes
 * @read_lock: mutex for recursive locking of @lock
 * @recursion: depth of recursion
 *
 * Data for each amdgpu device and process address space.
 */
struct amdgpu_mn {
        /* constant after initialisation */
        struct amdgpu_device    *adev;
        struct mm_struct        *mm;
        struct mmu_notifier     mn;
        enum amdgpu_mn_type     type;

        /* only used on destruction */
        struct work_struct      work;

        /* protected by adev->mn_lock */
        struct hlist_node       node;

        /* objects protected by lock */
        struct rw_semaphore     lock;
        struct rb_root_cached   objects;
        struct lock             read_lock;
        atomic_t                recursion;
};

/**
 * struct amdgpu_mn_node
 *
 * @it: interval node defining start-last of the affected address range
 * @bos: list of all BOs in the affected address range
 *
 * Manages all BOs which are affected of a certain range of address space.
 */
struct amdgpu_mn_node {
        struct interval_tree_node       it;
        struct list_head                bos;
};

/**
 * amdgpu_mn_destroy - destroy the MMU notifier
 *
 * @work: previously sheduled work item
 *
 * Lazy destroys the notifier from a work item
 */
static void amdgpu_mn_destroy(struct work_struct *work)
{
        struct amdgpu_mn *amn = container_of(work, struct amdgpu_mn, work);
        struct amdgpu_device *adev = amn->adev;
        struct amdgpu_mn_node *node, *next_node;
        struct amdgpu_bo *bo, *next_bo;

        mutex_lock(&adev->mn_lock);
        down_write(&amn->lock);
        hash_del(&amn->node);
        rbtree_postorder_for_each_entry_safe(node, next_node,
                                             &amn->objects.rb_root, it.rb) {
                list_for_each_entry_safe(bo, next_bo, &node->bos, mn_list) {
                        bo->mn = NULL;
                        list_del_init(&bo->mn_list);
                }
                kfree(node);
        }
        up_write(&amn->lock);
        mutex_unlock(&adev->mn_lock);
        mmu_notifier_unregister_no_release(&amn->mn, amn->mm);
        kfree(amn);
}

/**
 * amdgpu_mn_release - callback to notify about mm destruction
 *
 * @mn: our notifier
 * @mm: the mm this callback is about
 *
 * Shedule a work item to lazy destroy our notifier.
 */
static void amdgpu_mn_release(struct mmu_notifier *mn,
                              struct mm_struct *mm)
{
        struct amdgpu_mn *amn = container_of(mn, struct amdgpu_mn, mn);

        INIT_WORK(&amn->work, amdgpu_mn_destroy);
        schedule_work(&amn->work);
}


/**
 * amdgpu_mn_lock - take the write side lock for this notifier
 *
 * @mn: our notifier
 */
void amdgpu_mn_lock(struct amdgpu_mn *mn)
{
        if (mn)
                down_write(&mn->lock);
}

/**
 * amdgpu_mn_unlock - drop the write side lock for this notifier
 *
 * @mn: our notifier
 */
void amdgpu_mn_unlock(struct amdgpu_mn *mn)
{
        if (mn)
                up_write(&mn->lock);
}

/**
 * amdgpu_mn_read_lock - take the read side lock for this notifier
 *
 * @amn: our notifier
 */
static int amdgpu_mn_read_lock(struct amdgpu_mn *amn, bool blockable)
{
        if (blockable)
                mutex_lock(&amn->read_lock);
        else if (!mutex_trylock(&amn->read_lock))
                return -EAGAIN;

        if (atomic_inc_return(&amn->recursion) == 1)
                down_read_non_owner(&amn->lock);
        mutex_unlock(&amn->read_lock);

        return 0;
}

/**
 * amdgpu_mn_read_unlock - drop the read side lock for this notifier
 *
 * @amn: our notifier
 */
static void amdgpu_mn_read_unlock(struct amdgpu_mn *amn)
{
        if (atomic_dec_return(&amn->recursion) == 0)
                up_read_non_owner(&amn->lock);
}

/**
 * amdgpu_mn_invalidate_node - unmap all BOs of a node
 *
 * @node: the node with the BOs to unmap
 * @start: start of address range affected
 * @end: end of address range affected
 *
 * Block for operations on BOs to finish and mark pages as accessed and
 * potentially dirty.
 */
static void amdgpu_mn_invalidate_node(struct amdgpu_mn_node *node,
                                      unsigned long start,
                                      unsigned long end)
{
        struct amdgpu_bo *bo;
        long r;

        list_for_each_entry(bo, &node->bos, mn_list) {

                if (!amdgpu_ttm_tt_affect_userptr(bo->tbo.ttm, start, end))
                        continue;

                r = reservation_object_wait_timeout_rcu(bo->tbo.resv,
                        true, false, MAX_SCHEDULE_TIMEOUT);
                if (r <= 0)
                        DRM_ERROR("(%ld) failed to wait for user bo\n", r);

                amdgpu_ttm_tt_mark_user_pages(bo->tbo.ttm);
        }
}

/**
 * amdgpu_mn_invalidate_range_start_gfx - callback to notify about mm change
 *
 * @mn: our notifier
 * @mm: the mm this callback is about
 * @start: start of updated range
 * @end: end of updated range
 *
 * Block for operations on BOs to finish and mark pages as accessed and
 * potentially dirty.
 */
static int amdgpu_mn_invalidate_range_start_gfx(struct mmu_notifier *mn,
                                                 struct mm_struct *mm,
                                                 unsigned long start,
                                                 unsigned long end,
                                                 bool blockable)
{
        struct amdgpu_mn *amn = container_of(mn, struct amdgpu_mn, mn);
        struct interval_tree_node *it;

        /* notification is exclusive, but interval is inclusive */
        end -= 1;

        /* TODO we should be able to split locking for interval tree and
         * amdgpu_mn_invalidate_node
         */
        if (amdgpu_mn_read_lock(amn, blockable))
                return -EAGAIN;

        it = interval_tree_iter_first(&amn->objects, start, end);
        while (it) {
                struct amdgpu_mn_node *node;

                if (!blockable) {
                        amdgpu_mn_read_unlock(amn);
                        return -EAGAIN;
                }

                node = container_of(it, struct amdgpu_mn_node, it);
                it = interval_tree_iter_next(it, start, end);

                amdgpu_mn_invalidate_node(node, start, end);
        }

        return 0;
}

/**
 * amdgpu_mn_invalidate_range_start_hsa - callback to notify about mm change
 *
 * @mn: our notifier
 * @mm: the mm this callback is about
 * @start: start of updated range
 * @end: end of updated range
 *
 * We temporarily evict all BOs between start and end. This
 * necessitates evicting all user-mode queues of the process. The BOs
 * are restorted in amdgpu_mn_invalidate_range_end_hsa.
 */
static int amdgpu_mn_invalidate_range_start_hsa(struct mmu_notifier *mn,
                                                 struct mm_struct *mm,
                                                 unsigned long start,
                                                 unsigned long end,
                                                 bool blockable)
{
        struct amdgpu_mn *amn = container_of(mn, struct amdgpu_mn, mn);
        struct interval_tree_node *it;

        /* notification is exclusive, but interval is inclusive */
        end -= 1;

        if (amdgpu_mn_read_lock(amn, blockable))
                return -EAGAIN;

        it = interval_tree_iter_first(&amn->objects, start, end);
        while (it) {
                struct amdgpu_mn_node *node;
                struct amdgpu_bo *bo;

                if (!blockable) {
                        amdgpu_mn_read_unlock(amn);
                        return -EAGAIN;
                }

                node = container_of(it, struct amdgpu_mn_node, it);
                it = interval_tree_iter_next(it, start, end);

                list_for_each_entry(bo, &node->bos, mn_list) {
                        struct kgd_mem *mem = bo->kfd_bo;

                        if (amdgpu_ttm_tt_affect_userptr(bo->tbo.ttm,
                                                         start, end))
                                amdgpu_amdkfd_evict_userptr(mem, mm);
                }
        }

        return 0;
}

/**
 * amdgpu_mn_invalidate_range_end - callback to notify about mm change
 *
 * @mn: our notifier
 * @mm: the mm this callback is about
 * @start: start of updated range
 * @end: end of updated range
 *
 * Release the lock again to allow new command submissions.
 */
static void amdgpu_mn_invalidate_range_end(struct mmu_notifier *mn,
                                           struct mm_struct *mm,
                                           unsigned long start,
                                           unsigned long end)
{
        struct amdgpu_mn *amn = container_of(mn, struct amdgpu_mn, mn);

        amdgpu_mn_read_unlock(amn);
}

static const struct mmu_notifier_ops amdgpu_mn_ops[] = {
        [AMDGPU_MN_TYPE_GFX] = {
                .release = amdgpu_mn_release,
                .invalidate_range_start = amdgpu_mn_invalidate_range_start_gfx,
                .invalidate_range_end = amdgpu_mn_invalidate_range_end,
        },
        [AMDGPU_MN_TYPE_HSA] = {
                .release = amdgpu_mn_release,
                .invalidate_range_start = amdgpu_mn_invalidate_range_start_hsa,
                .invalidate_range_end = amdgpu_mn_invalidate_range_end,
        },
};

/* Low bits of any reasonable mm pointer will be unused due to struct
 * alignment. Use these bits to make a unique key from the mm pointer
 * and notifier type.
 */
#define AMDGPU_MN_KEY(mm, type) ((unsigned long)(mm) + (type))

/**
 * amdgpu_mn_get - create notifier context
 *
 * @adev: amdgpu device pointer
 * @type: type of MMU notifier context
 *
 * Creates a notifier context for current->mm.
 */
struct amdgpu_mn *amdgpu_mn_get(struct amdgpu_device *adev,
                                enum amdgpu_mn_type type)
{
        struct mm_struct *mm = current->mm;
        struct amdgpu_mn *amn;
        unsigned long key = AMDGPU_MN_KEY(mm, type);
        int r;

        mutex_lock(&adev->mn_lock);
        if (down_write_killable(&mm->mmap_sem)) {
                mutex_unlock(&adev->mn_lock);
                return ERR_PTR(-EINTR);
        }

        hash_for_each_possible(adev->mn_hash, amn, node, key)
                if (AMDGPU_MN_KEY(amn->mm, amn->type) == key)
                        goto release_locks;

        amn = kzalloc(sizeof(*amn), GFP_KERNEL);
        if (!amn) {
                amn = ERR_PTR(-ENOMEM);
                goto release_locks;
        }

        amn->adev = adev;
        amn->mm = mm;
        init_rwsem(&amn->lock);
        amn->type = type;
        amn->mn.ops = &amdgpu_mn_ops[type];
        amn->objects = RB_ROOT_CACHED;
        mutex_init(&amn->read_lock);
        atomic_set(&amn->recursion, 0);

        r = __mmu_notifier_register(&amn->mn, mm);
        if (r)
                goto free_amn;

        hash_add(adev->mn_hash, &amn->node, AMDGPU_MN_KEY(mm, type));

release_locks:
        up_write(&mm->mmap_sem);
        mutex_unlock(&adev->mn_lock);

        return amn;

free_amn:
        up_write(&mm->mmap_sem);
        mutex_unlock(&adev->mn_lock);
        kfree(amn);

        return ERR_PTR(r);
}

/**
 * amdgpu_mn_register - register a BO for notifier updates
 *
 * @bo: amdgpu buffer object
 * @addr: userptr addr we should monitor
 *
 * Registers an MMU notifier for the given BO at the specified address.
 * Returns 0 on success, -ERRNO if anything goes wrong.
 */
int amdgpu_mn_register(struct amdgpu_bo *bo, unsigned long addr)
{
        unsigned long end = addr + amdgpu_bo_size(bo) - 1;
        struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
        enum amdgpu_mn_type type =
                bo->kfd_bo ? AMDGPU_MN_TYPE_HSA : AMDGPU_MN_TYPE_GFX;
        struct amdgpu_mn *amn;
        struct amdgpu_mn_node *node = NULL, *new_node;
        struct list_head bos;
        struct interval_tree_node *it;

        amn = amdgpu_mn_get(adev, type);
        if (IS_ERR(amn))
                return PTR_ERR(amn);

        new_node = kmalloc(sizeof(*new_node), GFP_KERNEL);
        if (!new_node)
                return -ENOMEM;

        INIT_LIST_HEAD(&bos);

        down_write(&amn->lock);

        while ((it = interval_tree_iter_first(&amn->objects, addr, end))) {
                kfree(node);
                node = container_of(it, struct amdgpu_mn_node, it);
                interval_tree_remove(&node->it, &amn->objects);
                addr = min(it->start, addr);
                end = max(it->last, end);
                list_splice(&node->bos, &bos);
        }

        if (!node)
                node = new_node;
        else
                kfree(new_node);

        bo->mn = amn;

        node->it.start = addr;
        node->it.last = end;
        INIT_LIST_HEAD(&node->bos);
        list_splice(&bos, &node->bos);
        list_add(&bo->mn_list, &node->bos);

        interval_tree_insert(&node->it, &amn->objects);

        up_write(&amn->lock);

        return 0;
}

/**
 * amdgpu_mn_unregister - unregister a BO for notifier updates
 *
 * @bo: amdgpu buffer object
 *
 * Remove any registration of MMU notifier updates from the buffer object.
 */
void amdgpu_mn_unregister(struct amdgpu_bo *bo)
{
        struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
        struct amdgpu_mn *amn;
        struct list_head *head;

        mutex_lock(&adev->mn_lock);

        amn = bo->mn;
        if (amn == NULL) {
                mutex_unlock(&adev->mn_lock);
                return;
        }

        down_write(&amn->lock);

        /* save the next list entry for later */
        head = bo->mn_list.next;

        bo->mn = NULL;
        list_del_init(&bo->mn_list);

        if (list_empty(head)) {
                struct amdgpu_mn_node *node;

                node = container_of(head, struct amdgpu_mn_node, bos);
                interval_tree_remove(&node->it, &amn->objects);
                kfree(node);
        }

        up_write(&amn->lock);
        mutex_unlock(&adev->mn_lock);
}