/*
 * Copyright © 2011-2012 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:
 *    Ben Widawsky <ben@bwidawsk.net>
 *
 */

/*
 * This file implements HW context support. On gen5+ a HW context consists of an
 * opaque GPU object which is referenced at times of context saves and restores.
 * With RC6 enabled, the context is also referenced as the GPU enters and exists
 * from RC6 (GPU has it's own internal power context, except on gen5). Though
 * something like a context does exist for the media ring, the code only
 * supports contexts for the render ring.
 *
 * In software, there is a distinction between contexts created by the user,
 * and the default HW context. The default HW context is used by GPU clients
 * that do not request setup of their own hardware context. The default
 * context's state is never restored to help prevent programming errors. This
 * would happen if a client ran and piggy-backed off another clients GPU state.
 * The default context only exists to give the GPU some offset to load as the
 * current to invoke a save of the context we actually care about. In fact, the
 * code could likely be constructed, albeit in a more complicated fashion, to
 * never use the default context, though that limits the driver's ability to
 * swap out, and/or destroy other contexts.
 *
 * All other contexts are created as a request by the GPU client. These contexts
 * store GPU state, and thus allow GPU clients to not re-emit state (and
 * potentially query certain state) at any time. The kernel driver makes
 * certain that the appropriate commands are inserted.
 *
 * The context life cycle is semi-complicated in that context BOs may live
 * longer than the context itself because of the way the hardware, and object
 * tracking works. Below is a very crude representation of the state machine
 * describing the context life.
 *                                         refcount     pincount     active
 * S0: initial state                          0            0           0
 * S1: context created                        1            0           0
 * S2: context is currently running           2            1           X
 * S3: GPU referenced, but not current        2            0           1
 * S4: context is current, but destroyed      1            1           0
 * S5: like S3, but destroyed                 1            0           1
 *
 * The most common (but not all) transitions:
 * S0->S1: client creates a context
 * S1->S2: client submits execbuf with context
 * S2->S3: other clients submits execbuf with context
 * S3->S1: context object was retired
 * S3->S2: clients submits another execbuf
 * S2->S4: context destroy called with current context
 * S3->S5->S0: destroy path
 * S4->S5->S0: destroy path on current context
 *
 * There are two confusing terms used above:
 *  The "current context" means the context which is currently running on the
 *  GPU. The GPU has loaded its state already and has stored away the gtt
 *  offset of the BO. The GPU is not actively referencing the data at this
 *  offset, but it will on the next context switch. The only way to avoid this
 *  is to do a GPU reset.
 *
 *  An "active context' is one which was previously the "current context" and is
 *  on the active list waiting for the next context switch to occur. Until this
 *  happens, the object must remain at the same gtt offset. It is therefore
 *  possible to destroy a context, but it is still active.
 *
 */

#include <linux/log2.h>
#include <drm/drmP.h>
#include <drm/i915_drm.h>
#include "i915_drv.h"
#include "i915_trace.h"
#include "intel_workarounds.h"

#define ALL_L3_SLICES(dev) (1 << NUM_L3_SLICES(dev)) - 1

static void lut_close(struct i915_gem_context *ctx)
{
        struct i915_lut_handle *lut, *ln;
        struct radix_tree_iter iter;
        void __rcu **slot;

        list_for_each_entry_safe(lut, ln, &ctx->handles_list, ctx_link) {
                list_del(&lut->obj_link);
                kmem_cache_free(ctx->i915->luts, lut);
        }

        /* backport note:  __i915_gem_object_reset_page_iter() does
         * radix_tree_delete() within radix_tree_for_each_slot().  That
         * *may* end up being safe just because the case where a node
         * in the radix tree is removed and the tree shrunk happens
         * when we reach the end of a node.
         *
         * TODO look if we can get away with not restarting the loop
         * someday.. but I think this shouldn't be perf critical so
         * after bigger fires..
         */
        rcu_read_lock();
restart:
        radix_tree_for_each_slot(slot, &ctx->handles_vma, &iter, 0) {
                struct i915_vma *vma = rcu_dereference_raw(*slot);

                radix_tree_delete(&ctx->handles_vma, iter.index);

                __i915_gem_object_release_unless_active(vma->obj);
                goto restart;
        }
        rcu_read_unlock();
}

static inline int new_hw_id(struct drm_i915_private *i915, gfp_t gfp)
{
        unsigned int max;

        lockdep_assert_held(&i915->contexts.mutex);

        if (INTEL_GEN(i915) >= 11)
                max = GEN11_MAX_CONTEXT_HW_ID;
        else if (USES_GUC_SUBMISSION(i915))
                /*
                 * When using GuC in proxy submission, GuC consumes the
                 * highest bit in the context id to indicate proxy submission.
                 */
                max = MAX_GUC_CONTEXT_HW_ID;
        else
                max = MAX_CONTEXT_HW_ID;

        return ida_simple_get(&i915->contexts.hw_ida, 0, max, gfp);
}

static int steal_hw_id(struct drm_i915_private *i915)
{
        struct i915_gem_context *ctx, *cn;
        LIST_HEAD(pinned);
        int id = -ENOSPC;

        lockdep_assert_held(&i915->contexts.mutex);

        list_for_each_entry_safe(ctx, cn,
                                 &i915->contexts.hw_id_list, hw_id_link) {
                if (atomic_read(&ctx->hw_id_pin_count)) {
                        list_move_tail(&ctx->hw_id_link, &pinned);
                        continue;
                }

                GEM_BUG_ON(!ctx->hw_id); /* perma-pinned kernel context */
                list_del_init(&ctx->hw_id_link);
                id = ctx->hw_id;
                break;
        }

        /*
         * Remember how far we got up on the last repossesion scan, so the
         * list is kept in a "least recently scanned" order.
         */
        list_splice_tail(&pinned, &i915->contexts.hw_id_list);
        return id;
}

static int assign_hw_id(struct drm_i915_private *i915, unsigned int *out)
{
        int ret;

        lockdep_assert_held(&i915->contexts.mutex);

        /*
         * We prefer to steal/stall ourselves and our users over that of the
         * entire system. That may be a little unfair to our users, and
         * even hurt high priority clients. The choice is whether to oomkill
         * something else, or steal a context id.
         */
        ret = new_hw_id(i915, GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
        if (unlikely(ret < 0)) {
                ret = steal_hw_id(i915);
                if (ret < 0) /* once again for the correct errno code */
                        ret = new_hw_id(i915, GFP_KERNEL);
                if (ret < 0)
                        return ret;
        }

        *out = ret;
        return 0;
}

static void release_hw_id(struct i915_gem_context *ctx)
{
        struct drm_i915_private *i915 = ctx->i915;

        if (list_empty(&ctx->hw_id_link))
                return;

        mutex_lock(&i915->contexts.mutex);
        if (!list_empty(&ctx->hw_id_link)) {
                ida_simple_remove(&i915->contexts.hw_ida, ctx->hw_id);
                list_del_init(&ctx->hw_id_link);
        }
        mutex_unlock(&i915->contexts.mutex);
}

static void i915_gem_context_free(struct i915_gem_context *ctx)
{
        unsigned int n;

        lockdep_assert_held(&ctx->i915->drm.struct_mutex);
        GEM_BUG_ON(!i915_gem_context_is_closed(ctx));

        release_hw_id(ctx);
        i915_ppgtt_put(ctx->ppgtt);

        for (n = 0; n < ARRAY_SIZE(ctx->__engine); n++) {
                struct intel_context *ce = &ctx->__engine[n];

                if (ce->ops)
                        ce->ops->destroy(ce);
        }

        kfree(ctx->name);
        put_pid(ctx->pid);

        list_del(&ctx->link);

        kfree_rcu(ctx, rcu);
}

static void contexts_free(struct drm_i915_private *i915)
{
        struct llist_node *freed = llist_del_all(&i915->contexts.free_list);
        struct i915_gem_context *ctx, *cn;

        lockdep_assert_held(&i915->drm.struct_mutex);

        llist_for_each_entry_safe(ctx, cn, freed, free_link)
                i915_gem_context_free(ctx);
}

static void contexts_free_first(struct drm_i915_private *i915)
{
        struct i915_gem_context *ctx;
        struct llist_node *freed;

        lockdep_assert_held(&i915->drm.struct_mutex);

        freed = llist_del_first(&i915->contexts.free_list);
        if (!freed)
                return;

        ctx = container_of(freed, typeof(*ctx), free_link);
        i915_gem_context_free(ctx);
}

static void contexts_free_worker(struct work_struct *work)
{
        struct drm_i915_private *i915 =
                container_of(work, typeof(*i915), contexts.free_work);

        mutex_lock(&i915->drm.struct_mutex);
        contexts_free(i915);
        mutex_unlock(&i915->drm.struct_mutex);
}

void i915_gem_context_release(struct kref *ref)
{
        struct i915_gem_context *ctx = container_of(ref, typeof(*ctx), ref);
        struct drm_i915_private *i915 = ctx->i915;

        trace_i915_context_free(ctx);
        if (llist_add(&ctx->free_link, &i915->contexts.free_list))
                queue_work(i915->wq, &i915->contexts.free_work);
}

static void context_close(struct i915_gem_context *ctx)
{
        i915_gem_context_set_closed(ctx);

        /*
         * This context will never again be assinged to HW, so we can
         * reuse its ID for the next context.
         */
        release_hw_id(ctx);

        /*
         * The LUT uses the VMA as a backpointer to unref the object,
         * so we need to clear the LUT before we close all the VMA (inside
         * the ppgtt).
         */
        lut_close(ctx);
        if (ctx->ppgtt)
                i915_ppgtt_close(&ctx->ppgtt->vm);

        ctx->file_priv = ERR_PTR(-EBADF);
        i915_gem_context_put(ctx);
}

static u32 default_desc_template(const struct drm_i915_private *i915,
                                 const struct i915_hw_ppgtt *ppgtt)
{
        u32 address_mode;
        u32 desc;

        desc = GEN8_CTX_VALID | GEN8_CTX_PRIVILEGE;

        address_mode = INTEL_LEGACY_32B_CONTEXT;
        if (ppgtt && i915_vm_is_48bit(&ppgtt->vm))
                address_mode = INTEL_LEGACY_64B_CONTEXT;
        desc |= address_mode << GEN8_CTX_ADDRESSING_MODE_SHIFT;

        if (IS_GEN8(i915))
                desc |= GEN8_CTX_L3LLC_COHERENT;

        /* TODO: WaDisableLiteRestore when we start using semaphore
         * signalling between Command Streamers
         * ring->ctx_desc_template |= GEN8_CTX_FORCE_RESTORE;
         */

        return desc;
}

static struct i915_gem_context *
__create_hw_context(struct drm_i915_private *dev_priv,
                    struct drm_i915_file_private *file_priv)
{
        struct i915_gem_context *ctx;
        unsigned int n;
        int ret;

        ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
        if (ctx == NULL)
                return ERR_PTR(-ENOMEM);

        kref_init(&ctx->ref);
        list_add_tail(&ctx->link, &dev_priv->contexts.list);
        ctx->i915 = dev_priv;
        ctx->sched.priority = I915_USER_PRIORITY(I915_PRIORITY_NORMAL);

        for (n = 0; n < ARRAY_SIZE(ctx->__engine); n++) {
                struct intel_context *ce = &ctx->__engine[n];

                ce->gem_context = ctx;
        }

        INIT_RADIX_TREE(&ctx->handles_vma, GFP_KERNEL);
        INIT_LIST_HEAD(&ctx->handles_list);
        INIT_LIST_HEAD(&ctx->hw_id_link);

        /* Default context will never have a file_priv */
        ret = DEFAULT_CONTEXT_HANDLE;
        if (file_priv) {
                ret = idr_alloc(&file_priv->context_idr, ctx,
                                DEFAULT_CONTEXT_HANDLE, 0, GFP_KERNEL);
                if (ret < 0)
                        goto err_lut;
        }
        ctx->user_handle = ret;

        ctx->file_priv = file_priv;
        if (file_priv) {
                ctx->pid = get_task_pid(current, PIDTYPE_PID);
                ctx->name = kasprintf(GFP_KERNEL, "%s[%d]/%x",
                                      current->comm,
                                      pid_nr(ctx->pid),
                                      ctx->user_handle);
                if (!ctx->name) {
                        ret = -ENOMEM;
                        goto err_pid;
                }
        }

        /* NB: Mark all slices as needing a remap so that when the context first
         * loads it will restore whatever remap state already exists. If there
         * is no remap info, it will be a NOP. */
        ctx->remap_slice = ALL_L3_SLICES(dev_priv);

        i915_gem_context_set_bannable(ctx);
        ctx->ring_size = 4 * PAGE_SIZE;
        ctx->desc_template =
                default_desc_template(dev_priv, dev_priv->mm.aliasing_ppgtt);

        return ctx;

err_pid:
        put_pid(ctx->pid);
        idr_remove(&file_priv->context_idr, ctx->user_handle);
err_lut:
        context_close(ctx);
        return ERR_PTR(ret);
}

static void __destroy_hw_context(struct i915_gem_context *ctx,
                                 struct drm_i915_file_private *file_priv)
{
        idr_remove(&file_priv->context_idr, ctx->user_handle);
        context_close(ctx);
}

static struct i915_gem_context *
i915_gem_create_context(struct drm_i915_private *dev_priv,
                        struct drm_i915_file_private *file_priv)
{
        struct i915_gem_context *ctx;

        lockdep_assert_held(&dev_priv->drm.struct_mutex);

        /* Reap the most stale context */
        contexts_free_first(dev_priv);

        ctx = __create_hw_context(dev_priv, file_priv);
        if (IS_ERR(ctx))
                return ctx;

        if (HAS_FULL_PPGTT(dev_priv)) {
                struct i915_hw_ppgtt *ppgtt;

                ppgtt = i915_ppgtt_create(dev_priv, file_priv);
                if (IS_ERR(ppgtt)) {
                        DRM_DEBUG_DRIVER("PPGTT setup failed (%ld)\n",
                                         PTR_ERR(ppgtt));
                        __destroy_hw_context(ctx, file_priv);
                        return ERR_CAST(ppgtt);
                }

                ctx->ppgtt = ppgtt;
                ctx->desc_template = default_desc_template(dev_priv, ppgtt);
        }

        trace_i915_context_create(ctx);

        return ctx;
}

/**
 * i915_gem_context_create_gvt - create a GVT GEM context
 * @dev: drm device *
 *
 * This function is used to create a GVT specific GEM context.
 *
 * Returns:
 * pointer to i915_gem_context on success, error pointer if failed
 *
 */
struct i915_gem_context *
i915_gem_context_create_gvt(struct drm_device *dev)
{
        struct i915_gem_context *ctx;
        int ret;

        if (!IS_ENABLED(CONFIG_DRM_I915_GVT))
                return ERR_PTR(-ENODEV);

        ret = i915_mutex_lock_interruptible(dev);
        if (ret)
                return ERR_PTR(ret);

        ctx = i915_gem_create_context(to_i915(dev), NULL);
        if (IS_ERR(ctx))
                goto out;

        ctx->file_priv = ERR_PTR(-EBADF);
        i915_gem_context_set_closed(ctx); /* not user accessible */
        i915_gem_context_clear_bannable(ctx);
        i915_gem_context_set_force_single_submission(ctx);
        if (!USES_GUC_SUBMISSION(to_i915(dev)))
                ctx->ring_size = 512 * PAGE_SIZE; /* Max ring buffer size */

        GEM_BUG_ON(i915_gem_context_is_kernel(ctx));
out:
        mutex_unlock(&dev->struct_mutex);
        return ctx;
}

static void
destroy_kernel_context(struct i915_gem_context **ctxp)
{
        struct i915_gem_context *ctx;

        /* Keep the context ref so that we can free it immediately ourselves */
        ctx = i915_gem_context_get(fetch_and_zero(ctxp));
        GEM_BUG_ON(!i915_gem_context_is_kernel(ctx));

        context_close(ctx);
        i915_gem_context_free(ctx);
}

struct i915_gem_context *
i915_gem_context_create_kernel(struct drm_i915_private *i915, int prio)
{
        struct i915_gem_context *ctx;
        int err;

        ctx = i915_gem_create_context(i915, NULL);
        if (IS_ERR(ctx))
                return ctx;

        err = i915_gem_context_pin_hw_id(ctx);
        if (err) {
                destroy_kernel_context(&ctx);
                return ERR_PTR(err);
        }

        i915_gem_context_clear_bannable(ctx);
        ctx->sched.priority = I915_USER_PRIORITY(prio);
        ctx->ring_size = PAGE_SIZE;

        GEM_BUG_ON(!i915_gem_context_is_kernel(ctx));

        return ctx;
}

static void init_contexts(struct drm_i915_private *i915)
{
        mutex_init(&i915->contexts.mutex);
        INIT_LIST_HEAD(&i915->contexts.list);

        /* Using the simple ida interface, the max is limited by sizeof(int) */
        BUILD_BUG_ON(MAX_CONTEXT_HW_ID > INT_MAX);
        BUILD_BUG_ON(GEN11_MAX_CONTEXT_HW_ID > INT_MAX);
        ida_init(&i915->contexts.hw_ida);
        INIT_LIST_HEAD(&i915->contexts.hw_id_list);

        INIT_WORK(&i915->contexts.free_work, contexts_free_worker);
        init_llist_head(&i915->contexts.free_list);
}

static bool needs_preempt_context(struct drm_i915_private *i915)
{
        return HAS_LOGICAL_RING_PREEMPTION(i915);
}

int i915_gem_contexts_init(struct drm_i915_private *dev_priv)
{
        struct i915_gem_context *ctx;

        /* Reassure ourselves we are only called once */
        GEM_BUG_ON(dev_priv->kernel_context);
        GEM_BUG_ON(dev_priv->preempt_context);

        intel_engine_init_ctx_wa(dev_priv->engine[RCS]);
        init_contexts(dev_priv);

        /* lowest priority; idle task */
        ctx = i915_gem_context_create_kernel(dev_priv, I915_PRIORITY_MIN);
        if (IS_ERR(ctx)) {
                DRM_ERROR("Failed to create default global context\n");
                return PTR_ERR(ctx);
        }
        /*
         * For easy recognisablity, we want the kernel context to be 0 and then
         * all user contexts will have non-zero hw_id. Kernel contexts are
         * permanently pinned, so that we never suffer a stall and can
         * use them from any allocation context (e.g. for evicting other
         * contexts and from inside the shrinker).
         */
        GEM_BUG_ON(ctx->hw_id);
        GEM_BUG_ON(!atomic_read(&ctx->hw_id_pin_count));
        dev_priv->kernel_context = ctx;

        /* highest priority; preempting task */
        if (needs_preempt_context(dev_priv)) {
                ctx = i915_gem_context_create_kernel(dev_priv, INT_MAX);
                if (!IS_ERR(ctx))
                        dev_priv->preempt_context = ctx;
                else
                        DRM_ERROR("Failed to create preempt context; disabling preemption\n");
        }

        DRM_DEBUG_DRIVER("%s context support initialized\n",
                         DRIVER_CAPS(dev_priv)->has_logical_contexts ?
                         "logical" : "fake");
        return 0;
}

void i915_gem_contexts_lost(struct drm_i915_private *dev_priv)
{
        struct intel_engine_cs *engine;
        enum intel_engine_id id;

        lockdep_assert_held(&dev_priv->drm.struct_mutex);

        for_each_engine(engine, dev_priv, id)
                intel_engine_lost_context(engine);
}

void i915_gem_contexts_fini(struct drm_i915_private *i915)
{
        lockdep_assert_held(&i915->drm.struct_mutex);

        if (i915->preempt_context)
                destroy_kernel_context(&i915->preempt_context);
        destroy_kernel_context(&i915->kernel_context);

        /* Must free all deferred contexts (via flush_workqueue) first */
        GEM_BUG_ON(!list_empty(&i915->contexts.hw_id_list));
        ida_destroy(&i915->contexts.hw_ida);
}

static int context_idr_cleanup(int id, void *p, void *data)
{
        struct i915_gem_context *ctx = p;

        context_close(ctx);
        return 0;
}

int i915_gem_context_open(struct drm_i915_private *i915,
                          struct drm_file *file)
{
        struct drm_i915_file_private *file_priv = file->driver_priv;
        struct i915_gem_context *ctx;

        idr_init(&file_priv->context_idr);

        mutex_lock(&i915->drm.struct_mutex);
        ctx = i915_gem_create_context(i915, file_priv);
        mutex_unlock(&i915->drm.struct_mutex);
        if (IS_ERR(ctx)) {
                idr_destroy(&file_priv->context_idr);
                return PTR_ERR(ctx);
        }

        GEM_BUG_ON(i915_gem_context_is_kernel(ctx));

        return 0;
}

void i915_gem_context_close(struct drm_file *file)
{
        struct drm_i915_file_private *file_priv = file->driver_priv;

        lockdep_assert_held(&file_priv->dev_priv->drm.struct_mutex);

        idr_for_each(&file_priv->context_idr, context_idr_cleanup, NULL);
        idr_destroy(&file_priv->context_idr);
}

static struct i915_request *
last_request_on_engine(struct i915_timeline *timeline,
                       struct intel_engine_cs *engine)
{
        struct i915_request *rq;

        GEM_BUG_ON(timeline == &engine->timeline);

        rq = i915_gem_active_raw(&timeline->last_request,
                                 &engine->i915->drm.struct_mutex);
        if (rq && rq->engine == engine) {
                GEM_TRACE("last request for %s on engine %s: %llx:%d\n",
                          timeline->name, engine->name,
                          rq->fence.context, rq->fence.seqno);
                GEM_BUG_ON(rq->timeline != timeline);
                return rq;
        }

        return NULL;
}

static bool engine_has_kernel_context_barrier(struct intel_engine_cs *engine)
{
        struct drm_i915_private *i915 = engine->i915;
        const struct intel_context * const ce =
                to_intel_context(i915->kernel_context, engine);
        struct i915_timeline *barrier = ce->ring->timeline;
        struct intel_ring *ring;
        bool any_active = false;

        lockdep_assert_held(&i915->drm.struct_mutex);
        list_for_each_entry(ring, &i915->gt.active_rings, active_link) {
                struct i915_request *rq;

                rq = last_request_on_engine(ring->timeline, engine);
                if (!rq)
                        continue;

                any_active = true;

                if (rq->hw_context == ce)
                        continue;

                /*
                 * Was this request submitted after the previous
                 * switch-to-kernel-context?
                 */
                if (!i915_timeline_sync_is_later(barrier, &rq->fence)) {
                        GEM_TRACE("%s needs barrier for %llx:%d\n",
                                  ring->timeline->name,
                                  rq->fence.context,
                                  rq->fence.seqno);
                        return false;
                }

                GEM_TRACE("%s has barrier after %llx:%d\n",
                          ring->timeline->name,
                          rq->fence.context,
                          rq->fence.seqno);
        }

        /*
         * If any other timeline was still active and behind the last barrier,
         * then our last switch-to-kernel-context must still be queued and
         * will run last (leaving the engine in the kernel context when it
         * eventually idles).
         */
        if (any_active)
                return true;

        /* The engine is idle; check that it is idling in the kernel context. */
        return engine->last_retired_context == ce;
}

int i915_gem_switch_to_kernel_context(struct drm_i915_private *i915)
{
        struct intel_engine_cs *engine;
        enum intel_engine_id id;

        GEM_TRACE("awake?=%s\n", yesno(i915->gt.awake));

        lockdep_assert_held(&i915->drm.struct_mutex);
        GEM_BUG_ON(!i915->kernel_context);

        i915_retire_requests(i915);

        for_each_engine(engine, i915, id) {
                struct intel_ring *ring;
                struct i915_request *rq;

                GEM_BUG_ON(!to_intel_context(i915->kernel_context, engine));
                if (engine_has_kernel_context_barrier(engine))
                        continue;

                GEM_TRACE("emit barrier on %s\n", engine->name);

                rq = i915_request_alloc(engine, i915->kernel_context);
                if (IS_ERR(rq))
                        return PTR_ERR(rq);

                /* Queue this switch after all other activity */
                list_for_each_entry(ring, &i915->gt.active_rings, active_link) {
                        struct i915_request *prev;

                        prev = last_request_on_engine(ring->timeline, engine);
                        if (!prev)
                                continue;

                        if (prev->gem_context == i915->kernel_context)
                                continue;

                        GEM_TRACE("add barrier on %s for %llx:%d\n",
                                  engine->name,
                                  prev->fence.context,
                                  prev->fence.seqno);
                        i915_sw_fence_await_sw_fence_gfp(&rq->submit,
                                                         &prev->submit,
                                                         I915_FENCE_GFP);
                        i915_timeline_sync_set(rq->timeline, &prev->fence);
                }

                i915_request_add(rq);
        }

        return 0;
}

static bool client_is_banned(struct drm_i915_file_private *file_priv)
{
        return atomic_read(&file_priv->ban_score) >= I915_CLIENT_SCORE_BANNED;
}

int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
                                  struct drm_file *file)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct drm_i915_gem_context_create *args = data;
        struct drm_i915_file_private *file_priv = file->driver_priv;
        struct i915_gem_context *ctx;
        int ret;

        if (!DRIVER_CAPS(dev_priv)->has_logical_contexts)
                return -ENODEV;

        if (args->pad != 0)
                return -EINVAL;

        if (client_is_banned(file_priv)) {
                DRM_DEBUG("client %s[%d] banned from creating ctx\n",
                          current->comm,
                          pid_nr(get_task_pid(current, PIDTYPE_PID)));

                return -EIO;
        }

        ret = i915_mutex_lock_interruptible(dev);
        if (ret)
                return ret;

        ctx = i915_gem_create_context(dev_priv, file_priv);
        mutex_unlock(&dev->struct_mutex);
        if (IS_ERR(ctx))
                return PTR_ERR(ctx);

        GEM_BUG_ON(i915_gem_context_is_kernel(ctx));

        args->ctx_id = ctx->user_handle;
        DRM_DEBUG("HW context %d created\n", args->ctx_id);

        return 0;
}

int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
                                   struct drm_file *file)
{
        struct drm_i915_gem_context_destroy *args = data;
        struct drm_i915_file_private *file_priv = file->driver_priv;
        struct i915_gem_context *ctx;
        int ret;

        if (args->pad != 0)
                return -EINVAL;

        if (args->ctx_id == DEFAULT_CONTEXT_HANDLE)
                return -ENOENT;

        ctx = i915_gem_context_lookup(file_priv, args->ctx_id);
        if (!ctx)
                return -ENOENT;

        ret = mutex_lock_interruptible(&dev->struct_mutex);
        if (ret)
                goto out;

        __destroy_hw_context(ctx, file_priv);
        mutex_unlock(&dev->struct_mutex);

out:
        i915_gem_context_put(ctx);
        return 0;
}

int i915_gem_context_getparam_ioctl(struct drm_device *dev, void *data,
                                    struct drm_file *file)
{
        struct drm_i915_file_private *file_priv = file->driver_priv;
        struct drm_i915_gem_context_param *args = data;
        struct i915_gem_context *ctx;
        int ret = 0;

        ctx = i915_gem_context_lookup(file_priv, args->ctx_id);
        if (!ctx)
                return -ENOENT;

        args->size = 0;
        switch (args->param) {
        case I915_CONTEXT_PARAM_BAN_PERIOD:
                ret = -EINVAL;
                break;
        case I915_CONTEXT_PARAM_NO_ZEROMAP:
                args->value = test_bit(UCONTEXT_NO_ZEROMAP, &ctx->user_flags);
                break;
        case I915_CONTEXT_PARAM_GTT_SIZE:
                if (ctx->ppgtt)
                        args->value = ctx->ppgtt->vm.total;
                else if (to_i915(dev)->mm.aliasing_ppgtt)
                        args->value = to_i915(dev)->mm.aliasing_ppgtt->vm.total;
                else
                        args->value = to_i915(dev)->ggtt.vm.total;
                break;
        case I915_CONTEXT_PARAM_NO_ERROR_CAPTURE:
                args->value = i915_gem_context_no_error_capture(ctx);
                break;
        case I915_CONTEXT_PARAM_BANNABLE:
                args->value = i915_gem_context_is_bannable(ctx);
                break;
        case I915_CONTEXT_PARAM_PRIORITY:
                args->value = ctx->sched.priority >> I915_USER_PRIORITY_SHIFT;
                break;
        default:
                ret = -EINVAL;
                break;
        }

        i915_gem_context_put(ctx);
        return ret;
}

int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
                                    struct drm_file *file)
{
        struct drm_i915_file_private *file_priv = file->driver_priv;
        struct drm_i915_gem_context_param *args = data;
        struct i915_gem_context *ctx;
        int ret = 0;

        ctx = i915_gem_context_lookup(file_priv, args->ctx_id);
        if (!ctx)
                return -ENOENT;

        switch (args->param) {
        case I915_CONTEXT_PARAM_BAN_PERIOD:
                ret = -EINVAL;
                break;
        case I915_CONTEXT_PARAM_NO_ZEROMAP:
                if (args->size)
                        ret = -EINVAL;
                else if (args->value)
                        set_bit(UCONTEXT_NO_ZEROMAP, &ctx->user_flags);
                else
                        clear_bit(UCONTEXT_NO_ZEROMAP, &ctx->user_flags);
                break;
        case I915_CONTEXT_PARAM_NO_ERROR_CAPTURE:
                if (args->size)
                        ret = -EINVAL;
                else if (args->value)
                        i915_gem_context_set_no_error_capture(ctx);
                else
                        i915_gem_context_clear_no_error_capture(ctx);
                break;
        case I915_CONTEXT_PARAM_BANNABLE:
                if (args->size)
                        ret = -EINVAL;
                else if (!capable(CAP_SYS_ADMIN) && !args->value)
                        ret = -EPERM;
                else if (args->value)
                        i915_gem_context_set_bannable(ctx);
                else
                        i915_gem_context_clear_bannable(ctx);
                break;

        case I915_CONTEXT_PARAM_PRIORITY:
                {
                        s64 priority = args->value;

                        if (args->size)
                                ret = -EINVAL;
                        else if (!(to_i915(dev)->caps.scheduler & I915_SCHEDULER_CAP_PRIORITY))
                                ret = -ENODEV;
                        else if (priority > I915_CONTEXT_MAX_USER_PRIORITY ||
                                 priority < I915_CONTEXT_MIN_USER_PRIORITY)
                                ret = -EINVAL;
                        else if (priority > I915_CONTEXT_DEFAULT_PRIORITY &&
                                 !capable(CAP_SYS_NICE))
                                ret = -EPERM;
                        else
                                ctx->sched.priority =
                                        I915_USER_PRIORITY(priority);
                }
                break;

        default:
                ret = -EINVAL;
                break;
        }

        i915_gem_context_put(ctx);
        return ret;
}

int i915_gem_context_reset_stats_ioctl(struct drm_device *dev,
                                       void *data, struct drm_file *file)
{
        struct drm_i915_private *dev_priv = to_i915(dev);
        struct drm_i915_reset_stats *args = data;
        struct i915_gem_context *ctx;
        int ret;

        if (args->flags || args->pad)
                return -EINVAL;

        ret = -ENOENT;
        rcu_read_lock();
        ctx = __i915_gem_context_lookup_rcu(file->driver_priv, args->ctx_id);
        if (!ctx)
                goto out;

        /*
         * We opt for unserialised reads here. This may result in tearing
         * in the extremely unlikely event of a GPU hang on this context
         * as we are querying them. If we need that extra layer of protection,
         * we should wrap the hangstats with a seqlock.
         */

        if (capable(CAP_SYS_ADMIN))
                args->reset_count = i915_reset_count(&dev_priv->gpu_error);
        else

                args->reset_count = 0;

        args->batch_active = atomic_read(&ctx->guilty_count);
        args->batch_pending = atomic_read(&ctx->active_count);

        ret = 0;
out:
        rcu_read_unlock();
        return ret;
}

int __i915_gem_context_pin_hw_id(struct i915_gem_context *ctx)
{
        struct drm_i915_private *i915 = ctx->i915;
        int err = 0;

        mutex_lock(&i915->contexts.mutex);

        GEM_BUG_ON(i915_gem_context_is_closed(ctx));

        if (list_empty(&ctx->hw_id_link)) {
                GEM_BUG_ON(atomic_read(&ctx->hw_id_pin_count));

                err = assign_hw_id(i915, &ctx->hw_id);
                if (err)
                        goto out_unlock;

                list_add_tail(&ctx->hw_id_link, &i915->contexts.hw_id_list);
        }

        GEM_BUG_ON(atomic_read(&ctx->hw_id_pin_count) == ~0u);
        atomic_inc(&ctx->hw_id_pin_count);

out_unlock:
        mutex_unlock(&i915->contexts.mutex);
        return err;
}

#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftests/mock_context.c"
#include "selftests/i915_gem_context.c"
#endif