/*
 * Copyright © 2008-2010 Intel Corporation
 *
 * 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, sublicense,
 * 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 NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS 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:
 *    Eric Anholt <eric@anholt.net>
 *    Chris Wilson <chris@chris-wilson.co.uuk>
 *
 */

#include "gem/i915_gem_context.h"
#include "gt/intel_gt_requests.h"

#include "i915_drv.h"
#include "i915_trace.h"

I915_SELFTEST_DECLARE(static struct igt_evict_ctl {
        bool fail_if_busy:1;
} igt_evict_ctl;)

static int ggtt_flush(struct intel_gt *gt)
{
        /*
         * Not everything in the GGTT is tracked via vma (otherwise we
         * could evict as required with minimal stalling) so we are forced
         * to idle the GPU and explicitly retire outstanding requests in
         * the hopes that we can then remove contexts and the like only
         * bound by their active reference.
         */
        return intel_gt_wait_for_idle(gt, MAX_SCHEDULE_TIMEOUT);
}

static bool
mark_free(struct drm_mm_scan *scan,
          struct i915_vma *vma,
          unsigned int flags,
          struct list_head *unwind)
{
        if (i915_vma_is_pinned(vma))
                return false;

        list_add(&vma->evict_link, unwind);
        return drm_mm_scan_add_block(scan, &vma->node);
}

/**
 * i915_gem_evict_something - Evict vmas to make room for binding a new one
 * @vm: address space to evict from
 * @min_size: size of the desired free space
 * @alignment: alignment constraint of the desired free space
 * @color: color for the desired space
 * @start: start (inclusive) of the range from which to evict objects
 * @end: end (exclusive) of the range from which to evict objects
 * @flags: additional flags to control the eviction algorithm
 *
 * This function will try to evict vmas until a free space satisfying the
 * requirements is found. Callers must check first whether any such hole exists
 * already before calling this function.
 *
 * This function is used by the object/vma binding code.
 *
 * Since this function is only used to free up virtual address space it only
 * ignores pinned vmas, and not object where the backing storage itself is
 * pinned. Hence obj->pages_pin_count does not protect against eviction.
 *
 * To clarify: This is for freeing up virtual address space, not for freeing
 * memory in e.g. the shrinker.
 */
int
i915_gem_evict_something(struct i915_address_space *vm,
                         u64 min_size, u64 alignment,
                         unsigned long color,
                         u64 start, u64 end,
                         unsigned flags)
{
        struct drm_mm_scan scan;
        struct list_head eviction_list;
        struct i915_vma *vma, *next;
        struct drm_mm_node *node;
        enum drm_mm_insert_mode mode;
        struct i915_vma *active;
        int ret;

        lockdep_assert_held(&vm->mutex);
        trace_i915_gem_evict(vm, min_size, alignment, flags);

        /*
         * The goal is to evict objects and amalgamate space in rough LRU order.
         * Since both active and inactive objects reside on the same list,
         * in a mix of creation and last scanned order, as we process the list
         * we sort it into inactive/active, which keeps the active portion
         * in a rough MRU order.
         *
         * The retirement sequence is thus:
         *   1. Inactive objects (already retired, random order)
         *   2. Active objects (will stall on unbinding, oldest scanned first)
         */
        mode = DRM_MM_INSERT_BEST;
        if (flags & PIN_HIGH)
                mode = DRM_MM_INSERT_HIGH;
        if (flags & PIN_MAPPABLE)
                mode = DRM_MM_INSERT_LOW;
        drm_mm_scan_init_with_range(&scan, &vm->mm,
                                    min_size, alignment, color,
                                    start, end, mode);

        intel_gt_retire_requests(vm->gt);

search_again:
        active = NULL;
        INIT_LIST_HEAD(&eviction_list);
        list_for_each_entry_safe(vma, next, &vm->bound_list, vm_link) {
                if (vma == active) { /* now seen this vma twice */
                        if (flags & PIN_NONBLOCK)
                                break;

                        active = ERR_PTR(-EAGAIN);
                }

                /*
                 * We keep this list in a rough least-recently scanned order
                 * of active elements (inactive elements are cheap to reap).
                 * New entries are added to the end, and we move anything we
                 * scan to the end. The assumption is that the working set
                 * of applications is either steady state (and thanks to the
                 * userspace bo cache it almost always is) or volatile and
                 * frequently replaced after a frame, which are self-evicting!
                 * Given that assumption, the MRU order of the scan list is
                 * fairly static, and keeping it in least-recently scan order
                 * is suitable.
                 *
                 * To notice when we complete one full cycle, we record the
                 * first active element seen, before moving it to the tail.
                 */
                if (active != ERR_PTR(-EAGAIN) && i915_vma_is_active(vma)) {
                        if (!active)
                                active = vma;

                        list_move_tail(&vma->vm_link, &vm->bound_list);
                        continue;
                }

                if (mark_free(&scan, vma, flags, &eviction_list))
                        goto found;
        }

        /* Nothing found, clean up and bail out! */
        list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
                ret = drm_mm_scan_remove_block(&scan, &vma->node);
                BUG_ON(ret);
        }

        /*
         * Can we unpin some objects such as idle hw contents,
         * or pending flips? But since only the GGTT has global entries
         * such as scanouts, rinbuffers and contexts, we can skip the
         * purge when inspecting per-process local address spaces.
         */
        if (!i915_is_ggtt(vm) || flags & PIN_NONBLOCK)
                return -ENOSPC;

        /*
         * Not everything in the GGTT is tracked via VMA using
         * i915_vma_move_to_active(), otherwise we could evict as required
         * with minimal stalling. Instead we are forced to idle the GPU and
         * explicitly retire outstanding requests which will then remove
         * the pinning for active objects such as contexts and ring,
         * enabling us to evict them on the next iteration.
         *
         * To ensure that all user contexts are evictable, we perform
         * a switch to the perma-pinned kernel context. This all also gives
         * us a termination condition, when the last retired context is
         * the kernel's there is no more we can evict.
         */
        if (I915_SELFTEST_ONLY(igt_evict_ctl.fail_if_busy))
                return -EBUSY;

        ret = ggtt_flush(vm->gt);
        if (ret)
                return ret;

        cond_resched();

        flags |= PIN_NONBLOCK;
        goto search_again;

found:
        /* drm_mm doesn't allow any other other operations while
         * scanning, therefore store to-be-evicted objects on a
         * temporary list and take a reference for all before
         * calling unbind (which may remove the active reference
         * of any of our objects, thus corrupting the list).
         */
        list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
                if (drm_mm_scan_remove_block(&scan, &vma->node))
                        __i915_vma_pin(vma);
                else
                        list_del(&vma->evict_link);
        }

        /* Unbinding will emit any required flushes */
        ret = 0;
        list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
                __i915_vma_unpin(vma);
                if (ret == 0)
                        ret = __i915_vma_unbind(vma);
        }

        while (ret == 0 && (node = drm_mm_scan_color_evict(&scan))) {
                vma = container_of(node, struct i915_vma, node);

                /* If we find any non-objects (!vma), we cannot evict them */
                if (vma->node.color != I915_COLOR_UNEVICTABLE)
                        ret = __i915_vma_unbind(vma);
                else
                        ret = -ENOSPC; /* XXX search failed, try again? */
        }

        return ret;
}

/**
 * i915_gem_evict_for_node - Evict vmas to make room for binding a new one
 * @vm: address space to evict from
 * @target: range (and color) to evict for
 * @flags: additional flags to control the eviction algorithm
 *
 * This function will try to evict vmas that overlap the target node.
 *
 * To clarify: This is for freeing up virtual address space, not for freeing
 * memory in e.g. the shrinker.
 */
int i915_gem_evict_for_node(struct i915_address_space *vm,
                            struct drm_mm_node *target,
                            unsigned int flags)
{
        LIST_HEAD(eviction_list);
        struct drm_mm_node *node;
        u64 start = target->start;
        u64 end = start + target->size;
        struct i915_vma *vma, *next;
        int ret = 0;

        lockdep_assert_held(&vm->mutex);
        GEM_BUG_ON(!IS_ALIGNED(start, I915_GTT_PAGE_SIZE));
        GEM_BUG_ON(!IS_ALIGNED(end, I915_GTT_PAGE_SIZE));

        trace_i915_gem_evict_node(vm, target, flags);

        /*
         * Retire before we search the active list. Although we have
         * reasonable accuracy in our retirement lists, we may have
         * a stray pin (preventing eviction) that can only be resolved by
         * retiring.
         */
        intel_gt_retire_requests(vm->gt);

        if (i915_vm_has_cache_coloring(vm)) {
                /* Expand search to cover neighbouring guard pages (or lack!) */
                if (start)
                        start -= I915_GTT_PAGE_SIZE;

                /* Always look at the page afterwards to avoid the end-of-GTT */
                end += I915_GTT_PAGE_SIZE;
        }
        GEM_BUG_ON(start >= end);

        drm_mm_for_each_node_in_range(node, &vm->mm, start, end) {
                /* If we find any non-objects (!vma), we cannot evict them */
                if (node->color == I915_COLOR_UNEVICTABLE) {
                        ret = -ENOSPC;
                        break;
                }

                GEM_BUG_ON(!drm_mm_node_allocated(node));
                vma = container_of(node, typeof(*vma), node);

                /*
                 * If we are using coloring to insert guard pages between
                 * different cache domains within the address space, we have
                 * to check whether the objects on either side of our range
                 * abutt and conflict. If they are in conflict, then we evict
                 * those as well to make room for our guard pages.
                 */
                if (i915_vm_has_cache_coloring(vm)) {
                        if (node->start + node->size == target->start) {
                                if (node->color == target->color)
                                        continue;
                        }
                        if (node->start == target->start + target->size) {
                                if (node->color == target->color)
                                        continue;
                        }
                }

                if (i915_vma_is_pinned(vma)) {
                        ret = -ENOSPC;
                        break;
                }

                if (flags & PIN_NONBLOCK && i915_vma_is_active(vma)) {
                        ret = -ENOSPC;
                        break;
                }

                /*
                 * Never show fear in the face of dragons!
                 *
                 * We cannot directly remove this node from within this
                 * iterator and as with i915_gem_evict_something() we employ
                 * the vma pin_count in order to prevent the action of
                 * unbinding one vma from freeing (by dropping its active
                 * reference) another in our eviction list.
                 */
                __i915_vma_pin(vma);
                list_add(&vma->evict_link, &eviction_list);
        }

        list_for_each_entry_safe(vma, next, &eviction_list, evict_link) {
                __i915_vma_unpin(vma);
                if (ret == 0)
                        ret = __i915_vma_unbind(vma);
        }

        return ret;
}

/**
 * i915_gem_evict_vm - Evict all idle vmas from a vm
 * @vm: Address space to cleanse
 *
 * This function evicts all vmas from a vm.
 *
 * This is used by the execbuf code as a last-ditch effort to defragment the
 * address space.
 *
 * To clarify: This is for freeing up virtual address space, not for freeing
 * memory in e.g. the shrinker.
 */
int i915_gem_evict_vm(struct i915_address_space *vm)
{
        int ret = 0;

        lockdep_assert_held(&vm->mutex);
        trace_i915_gem_evict_vm(vm);

        /* Switch back to the default context in order to unpin
         * the existing context objects. However, such objects only
         * pin themselves inside the global GTT and performing the
         * switch otherwise is ineffective.
         */
        if (i915_is_ggtt(vm)) {
                ret = ggtt_flush(vm->gt);
                if (ret)
                        return ret;
        }

        do {
                struct i915_vma *vma, *vn;
                LIST_HEAD(eviction_list);

                list_for_each_entry(vma, &vm->bound_list, vm_link) {
                        if (i915_vma_is_pinned(vma))
                                continue;

                        __i915_vma_pin(vma);
                        list_add(&vma->evict_link, &eviction_list);
                }
                if (list_empty(&eviction_list))
                        break;

                ret = 0;
                list_for_each_entry_safe(vma, vn, &eviction_list, evict_link) {
                        __i915_vma_unpin(vma);
                        if (ret == 0)
                                ret = __i915_vma_unbind(vma);
                        if (ret != -EINTR) /* "Get me out of here!" */
                                ret = 0;
                }
        } while (ret == 0);

        return ret;
}

#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftests/i915_gem_evict.c"
#endif