/**************************************************************************
 *
 * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
 * 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 above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
 * 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.
 *
 **************************************************************************/
/*
 * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
 */

#define pr_fmt(fmt) "[TTM] " fmt

#include <ttm/ttm_module.h>
#include <ttm/ttm_bo_driver.h>
#include <ttm/ttm_placement.h>
#include <drm/drm_vma_manager.h>
#include <linux/mm.h>
#include <linux/rbtree.h>
#include <linux/module.h>
#include <linux/uaccess.h>

#define TTM_BO_VM_NUM_PREFAULT 16

static int ttm_bo_vm_fault_idle(struct ttm_buffer_object *bo,
                                struct vm_area_struct *vma,
                                struct vm_fault *vmf)
{
        int ret = 0;

        if (likely(!test_bit(TTM_BO_PRIV_FLAG_MOVING, &bo->priv_flags)))
                goto out_unlock;

        /*
         * Quick non-stalling check for idle.
         */
        ret = ttm_bo_wait(bo, false, false, true);
        if (likely(ret == 0))
                goto out_unlock;

        /*
         * If possible, avoid waiting for GPU with mmap_sem
         * held.
         */
        if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
                ret = VM_FAULT_RETRY;
                if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
                        goto out_unlock;

                up_read(&vma->vm_mm->mmap_sem);
                (void) ttm_bo_wait(bo, false, true, false);
                goto out_unlock;
        }

        /*
         * Ordinary wait.
         */
        ret = ttm_bo_wait(bo, false, true, false);
        if (unlikely(ret != 0))
                ret = (ret != -ERESTARTSYS) ? VM_FAULT_SIGBUS :
                        VM_FAULT_NOPAGE;

out_unlock:
        return ret;
}

static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        struct ttm_buffer_object *bo = (struct ttm_buffer_object *)
            vma->vm_private_data;
        struct ttm_bo_device *bdev = bo->bdev;
        unsigned long page_offset;
        unsigned long page_last;
        unsigned long pfn;
        struct ttm_tt *ttm = NULL;
        struct page *page;
        int ret;
        int i;
        unsigned long address = (unsigned long)vmf->virtual_address;
        int retval = VM_FAULT_NOPAGE;
        struct ttm_mem_type_manager *man =
                &bdev->man[bo->mem.mem_type];
        struct vm_area_struct cvma;

        /*
         * Work around locking order reversal in fault / nopfn
         * between mmap_sem and bo_reserve: Perform a trylock operation
         * for reserve, and if it fails, retry the fault after waiting
         * for the buffer to become unreserved.
         */
        ret = ttm_bo_reserve(bo, true, true, false, NULL);
        if (unlikely(ret != 0)) {
                if (ret != -EBUSY)
                        return VM_FAULT_NOPAGE;

                if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
                        if (!(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
                                up_read(&vma->vm_mm->mmap_sem);
                                (void) ttm_bo_wait_unreserved(bo);
                        }

                        return VM_FAULT_RETRY;
                }

                /*
                 * If we'd want to change locking order to
                 * mmap_sem -> bo::reserve, we'd use a blocking reserve here
                 * instead of retrying the fault...
                 */
                return VM_FAULT_NOPAGE;
        }

        /*
         * Refuse to fault imported pages. This should be handled
         * (if at all) by redirecting mmap to the exporter.
         */
        if (bo->ttm && (bo->ttm->page_flags & TTM_PAGE_FLAG_SG)) {
                retval = VM_FAULT_SIGBUS;
                goto out_unlock;
        }

        if (bdev->driver->fault_reserve_notify) {
                ret = bdev->driver->fault_reserve_notify(bo);
                switch (ret) {
                case 0:
                        break;
                case -EBUSY:
                case -ERESTARTSYS:
                        retval = VM_FAULT_NOPAGE;
                        goto out_unlock;
                default:
                        retval = VM_FAULT_SIGBUS;
                        goto out_unlock;
                }
        }

        /*
         * Wait for buffer data in transit, due to a pipelined
         * move.
         */
        ret = ttm_bo_vm_fault_idle(bo, vma, vmf);
        if (unlikely(ret != 0)) {
                retval = ret;
                goto out_unlock;
        }

        ret = ttm_mem_io_lock(man, true);
        if (unlikely(ret != 0)) {
                retval = VM_FAULT_NOPAGE;
                goto out_unlock;
        }
        ret = ttm_mem_io_reserve_vm(bo);
        if (unlikely(ret != 0)) {
                retval = VM_FAULT_SIGBUS;
                goto out_io_unlock;
        }

        page_offset = ((address - vma->vm_start) >> PAGE_SHIFT) +
                vma->vm_pgoff - drm_vma_node_start(&bo->vma_node);
        page_last = vma_pages(vma) + vma->vm_pgoff -
                drm_vma_node_start(&bo->vma_node);

        if (unlikely(page_offset >= bo->num_pages)) {
                retval = VM_FAULT_SIGBUS;
                goto out_io_unlock;
        }

        /*
         * Make a local vma copy to modify the page_prot member
         * and vm_flags if necessary. The vma parameter is protected
         * by mmap_sem in write mode.
         */
        cvma = *vma;
        cvma.vm_page_prot = vm_get_page_prot(cvma.vm_flags);

        if (bo->mem.bus.is_iomem) {
                cvma.vm_page_prot = ttm_io_prot(bo->mem.placement,
                                                cvma.vm_page_prot);
        } else {
                ttm = bo->ttm;
                cvma.vm_page_prot = ttm_io_prot(bo->mem.placement,
                                                cvma.vm_page_prot);

                /* Allocate all page at once, most common usage */
                if (ttm->bdev->driver->ttm_tt_populate(ttm)) {
                        retval = VM_FAULT_OOM;
                        goto out_io_unlock;
                }
        }

        /*
         * Speculatively prefault a number of pages. Only error on
         * first page.
         */
        for (i = 0; i < TTM_BO_VM_NUM_PREFAULT; ++i) {
                if (bo->mem.bus.is_iomem)
                        pfn = ((bo->mem.bus.base + bo->mem.bus.offset) >> PAGE_SHIFT) + page_offset;
                else {
                        page = ttm->pages[page_offset];
                        if (unlikely(!page && i == 0)) {
                                retval = VM_FAULT_OOM;
                                goto out_io_unlock;
                        } else if (unlikely(!page)) {
                                break;
                        }
                        page->mapping = vma->vm_file->f_mapping;
                        page->index = drm_vma_node_start(&bo->vma_node) +
                                page_offset;
                        pfn = page_to_pfn(page);
                }

                if (vma->vm_flags & VM_MIXEDMAP)
                        ret = vm_insert_mixed(&cvma, address, pfn);
                else
                        ret = vm_insert_pfn(&cvma, address, pfn);

                /*
                 * Somebody beat us to this PTE or prefaulting to
                 * an already populated PTE, or prefaulting error.
                 */

                if (unlikely((ret == -EBUSY) || (ret != 0 && i > 0)))
                        break;
                else if (unlikely(ret != 0)) {
                        retval =
                            (ret == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS;
                        goto out_io_unlock;
                }

                address += PAGE_SIZE;
                if (unlikely(++page_offset >= page_last))
                        break;
        }
out_io_unlock:
        ttm_mem_io_unlock(man);
out_unlock:
        ttm_bo_unreserve(bo);
        return retval;
}

static void ttm_bo_vm_open(struct vm_area_struct *vma)
{
        struct ttm_buffer_object *bo =
            (struct ttm_buffer_object *)vma->vm_private_data;

        WARN_ON(bo->bdev->dev_mapping != vma->vm_file->f_mapping);

        (void)ttm_bo_reference(bo);
}

static void ttm_bo_vm_close(struct vm_area_struct *vma)
{
        struct ttm_buffer_object *bo = (struct ttm_buffer_object *)vma->vm_private_data;

        ttm_bo_unref(&bo);
        vma->vm_private_data = NULL;
}

static const struct vm_operations_struct ttm_bo_vm_ops = {
        .fault = ttm_bo_vm_fault,
        .open = ttm_bo_vm_open,
        .close = ttm_bo_vm_close
};

static struct ttm_buffer_object *ttm_bo_vm_lookup(struct ttm_bo_device *bdev,
                                                  unsigned long offset,
                                                  unsigned long pages)
{
        struct drm_vma_offset_node *node;
        struct ttm_buffer_object *bo = NULL;

        drm_vma_offset_lock_lookup(&bdev->vma_manager);

        node = drm_vma_offset_lookup_locked(&bdev->vma_manager, offset, pages);
        if (likely(node)) {
                bo = container_of(node, struct ttm_buffer_object, vma_node);
                if (!kref_get_unless_zero(&bo->kref))
                        bo = NULL;
        }

        drm_vma_offset_unlock_lookup(&bdev->vma_manager);

        if (!bo)
                pr_err("Could not find buffer object to map\n");

        return bo;
}

int ttm_bo_mmap(struct file *filp, struct vm_area_struct *vma,
                struct ttm_bo_device *bdev)
{
        struct ttm_bo_driver *driver;
        struct ttm_buffer_object *bo;
        int ret;

        bo = ttm_bo_vm_lookup(bdev, vma->vm_pgoff, vma_pages(vma));
        if (unlikely(!bo))
                return -EINVAL;

        driver = bo->bdev->driver;
        if (unlikely(!driver->verify_access)) {
                ret = -EPERM;
                goto out_unref;
        }
        ret = driver->verify_access(bo, filp);
        if (unlikely(ret != 0))
                goto out_unref;

        vma->vm_ops = &ttm_bo_vm_ops;

        /*
         * Note: We're transferring the bo reference to
         * vma->vm_private_data here.
         */

        vma->vm_private_data = bo;

        /*
         * We'd like to use VM_PFNMAP on shared mappings, where
         * (vma->vm_flags & VM_SHARED) != 0, for performance reasons,
         * but for some reason VM_PFNMAP + x86 PAT + write-combine is very
         * bad for performance. Until that has been sorted out, use
         * VM_MIXEDMAP on all mappings. See freedesktop.org bug #75719
         */
        vma->vm_flags |= VM_MIXEDMAP;
        vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
        return 0;
out_unref:
        ttm_bo_unref(&bo);
        return ret;
}
EXPORT_SYMBOL(ttm_bo_mmap);

int ttm_fbdev_mmap(struct vm_area_struct *vma, struct ttm_buffer_object *bo)
{
        if (vma->vm_pgoff != 0)
                return -EACCES;

        vma->vm_ops = &ttm_bo_vm_ops;
        vma->vm_private_data = ttm_bo_reference(bo);
        vma->vm_flags |= VM_MIXEDMAP;
        vma->vm_flags |= VM_IO | VM_DONTEXPAND;
        return 0;
}
EXPORT_SYMBOL(ttm_fbdev_mmap);