Merge remote-tracking branches 'asoc/topic/ac97', 'asoc/topic/ac97-mfd', 'asoc/topic...

[mirror_ubuntu-focal-kernel.git] / drivers / gpu / drm / i915 / i915_gem_context.c

/*
 * 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"

#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);
        }

        rcu_read_lock();
        radix_tree_for_each_slot(slot, &ctx->handles_vma, &iter, 0) {
                struct i915_vma *vma = rcu_dereference_raw(*slot);
                struct drm_i915_gem_object *obj = vma->obj;

                radix_tree_iter_delete(&ctx->handles_vma, &iter, slot);

                if (!i915_vma_is_ggtt(vma))
                        i915_vma_close(vma);

                __i915_gem_object_release_unless_active(obj);
        }
        rcu_read_unlock();
}

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

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

        i915_ppgtt_put(ctx->ppgtt);

        for (i = 0; i < I915_NUM_ENGINES; i++) {
                struct intel_context *ce = &ctx->engine[i];

                if (!ce->state)
                        continue;

                WARN_ON(ce->pin_count);
                if (ce->ring)
                        intel_ring_free(ce->ring);

                __i915_gem_object_release_unless_active(ce->state->obj);
        }

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

        list_del(&ctx->link);

        ida_simple_remove(&ctx->i915->contexts.hw_ida, ctx->hw_id);
        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);

        lut_close(ctx);
        if (ctx->ppgtt)
                i915_ppgtt_close(&ctx->ppgtt->base);

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

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

        ret = ida_simple_get(&dev_priv->contexts.hw_ida,
                             0, MAX_CONTEXT_HW_ID, GFP_KERNEL);
        if (ret < 0) {
                /* Contexts are only released when no longer active.
                 * Flush any pending retires to hopefully release some
                 * stale contexts and try again.
                 */
                i915_gem_retire_requests(dev_priv);
                ret = ida_simple_get(&dev_priv->contexts.hw_ida,
                                     0, MAX_CONTEXT_HW_ID, GFP_KERNEL);
                if (ret < 0)
                        return ret;
        }

        *out = ret;
        return 0;
}

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->base))
                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;
        int ret;

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

        ret = assign_hw_id(dev_priv, &ctx->hw_id);
        if (ret) {
                kfree(ctx);
                return ERR_PTR(ret);
        }

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

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

        /* 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);

        /* GuC requires the ring to be placed above GUC_WOPCM_TOP. If GuC is not
         * present or not in use we still need a small bias as ring wraparound
         * at offset 0 sometimes hangs. No idea why.
         */
        if (HAS_GUC(dev_priv) && i915.enable_guc_loading)
                ctx->ggtt_offset_bias = GUC_WOPCM_TOP;
        else
                ctx->ggtt_offset_bias = I915_GTT_PAGE_SIZE;

        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);
}

/**
 * The default context needs to exist per ring that uses contexts. It stores the
 * context state of the GPU for applications that don't utilize HW contexts, as
 * well as an idle case.
 */
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 (USES_FULL_PPGTT(dev_priv)) {
                struct i915_hw_ppgtt *ppgtt;

                ppgtt = i915_ppgtt_create(dev_priv, file_priv, ctx->name);
                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 = __create_hw_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 (!i915.enable_guc_submission)
                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;
}

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

        /* Init should only be called once per module load. Eventually the
         * restriction on the context_disabled check can be loosened. */
        if (WARN_ON(dev_priv->kernel_context))
                return 0;

        INIT_LIST_HEAD(&dev_priv->contexts.list);
        INIT_WORK(&dev_priv->contexts.free_work, contexts_free_worker);
        init_llist_head(&dev_priv->contexts.free_list);

        if (intel_vgpu_active(dev_priv) &&
            HAS_LOGICAL_RING_CONTEXTS(dev_priv)) {
                if (!i915.enable_execlists) {
                        DRM_INFO("Only EXECLIST mode is supported in vgpu.\n");
                        return -EINVAL;
                }
        }

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

        ctx = i915_gem_create_context(dev_priv, NULL);
        if (IS_ERR(ctx)) {
                DRM_ERROR("Failed to create default global context (error %ld)\n",
                          PTR_ERR(ctx));
                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.
         */
        GEM_BUG_ON(ctx->hw_id);

        i915_gem_context_clear_bannable(ctx);
        ctx->priority = I915_PRIORITY_MIN; /* lowest priority; idle task */
        dev_priv->kernel_context = ctx;

        GEM_BUG_ON(!i915_gem_context_is_kernel(ctx));

        DRM_DEBUG_DRIVER("%s context support initialized\n",
                         dev_priv->engine[RCS]->context_size ? "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) {
                engine->legacy_active_context = NULL;

                if (!engine->last_retired_context)
                        continue;

                engine->context_unpin(engine, engine->last_retired_context);
                engine->last_retired_context = NULL;
        }

        /* Force the GPU state to be restored on enabling */
        if (!i915.enable_execlists) {
                struct i915_gem_context *ctx;

                list_for_each_entry(ctx, &dev_priv->contexts.list, link) {
                        if (!i915_gem_context_is_default(ctx))
                                continue;

                        for_each_engine(engine, dev_priv, id)
                                ctx->engine[engine->id].initialised = false;

                        ctx->remap_slice = ALL_L3_SLICES(dev_priv);
                }

                for_each_engine(engine, dev_priv, id) {
                        struct intel_context *kce =
                                &dev_priv->kernel_context->engine[engine->id];

                        kce->initialised = true;
                }
        }
}

void i915_gem_contexts_fini(struct drm_i915_private *i915)
{
        struct i915_gem_context *ctx;

        lockdep_assert_held(&i915->drm.struct_mutex);

        /* Keep the context so that we can free it immediately ourselves */
        ctx = i915_gem_context_get(fetch_and_zero(&i915->kernel_context));
        GEM_BUG_ON(!i915_gem_context_is_kernel(ctx));
        context_close(ctx);
        i915_gem_context_free(ctx);

        /* Must free all deferred contexts (via flush_workqueue) first */
        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 inline int
mi_set_context(struct drm_i915_gem_request *req, u32 flags)
{
        struct drm_i915_private *dev_priv = req->i915;
        struct intel_engine_cs *engine = req->engine;
        enum intel_engine_id id;
        const int num_rings =
                /* Use an extended w/a on gen7 if signalling from other rings */
                (i915.semaphores && INTEL_GEN(dev_priv) == 7) ?
                INTEL_INFO(dev_priv)->num_rings - 1 :
                0;
        int len;
        u32 *cs;

        flags |= MI_MM_SPACE_GTT;
        if (IS_HASWELL(dev_priv) || INTEL_GEN(dev_priv) >= 8)
                /* These flags are for resource streamer on HSW+ */
                flags |= HSW_MI_RS_SAVE_STATE_EN | HSW_MI_RS_RESTORE_STATE_EN;
        else
                flags |= MI_SAVE_EXT_STATE_EN | MI_RESTORE_EXT_STATE_EN;

        len = 4;
        if (INTEL_GEN(dev_priv) >= 7)
                len += 2 + (num_rings ? 4*num_rings + 6 : 0);

        cs = intel_ring_begin(req, len);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        /* WaProgramMiArbOnOffAroundMiSetContext:ivb,vlv,hsw,bdw,chv */
        if (INTEL_GEN(dev_priv) >= 7) {
                *cs++ = MI_ARB_ON_OFF | MI_ARB_DISABLE;
                if (num_rings) {
                        struct intel_engine_cs *signaller;

                        *cs++ = MI_LOAD_REGISTER_IMM(num_rings);
                        for_each_engine(signaller, dev_priv, id) {
                                if (signaller == engine)
                                        continue;

                                *cs++ = i915_mmio_reg_offset(
                                           RING_PSMI_CTL(signaller->mmio_base));
                                *cs++ = _MASKED_BIT_ENABLE(
                                                GEN6_PSMI_SLEEP_MSG_DISABLE);
                        }
                }
        }

        *cs++ = MI_NOOP;
        *cs++ = MI_SET_CONTEXT;
        *cs++ = i915_ggtt_offset(req->ctx->engine[RCS].state) | flags;
        /*
         * w/a: MI_SET_CONTEXT must always be followed by MI_NOOP
         * WaMiSetContext_Hang:snb,ivb,vlv
         */
        *cs++ = MI_NOOP;

        if (INTEL_GEN(dev_priv) >= 7) {
                if (num_rings) {
                        struct intel_engine_cs *signaller;
                        i915_reg_t last_reg = {}; /* keep gcc quiet */

                        *cs++ = MI_LOAD_REGISTER_IMM(num_rings);
                        for_each_engine(signaller, dev_priv, id) {
                                if (signaller == engine)
                                        continue;

                                last_reg = RING_PSMI_CTL(signaller->mmio_base);
                                *cs++ = i915_mmio_reg_offset(last_reg);
                                *cs++ = _MASKED_BIT_DISABLE(
                                                GEN6_PSMI_SLEEP_MSG_DISABLE);
                        }

                        /* Insert a delay before the next switch! */
                        *cs++ = MI_STORE_REGISTER_MEM | MI_SRM_LRM_GLOBAL_GTT;
                        *cs++ = i915_mmio_reg_offset(last_reg);
                        *cs++ = i915_ggtt_offset(engine->scratch);
                        *cs++ = MI_NOOP;
                }
                *cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
        }

        intel_ring_advance(req, cs);

        return 0;
}

static int remap_l3(struct drm_i915_gem_request *req, int slice)
{
        u32 *cs, *remap_info = req->i915->l3_parity.remap_info[slice];
        int i;

        if (!remap_info)
                return 0;

        cs = intel_ring_begin(req, GEN7_L3LOG_SIZE/4 * 2 + 2);
        if (IS_ERR(cs))
                return PTR_ERR(cs);

        /*
         * Note: We do not worry about the concurrent register cacheline hang
         * here because no other code should access these registers other than
         * at initialization time.
         */
        *cs++ = MI_LOAD_REGISTER_IMM(GEN7_L3LOG_SIZE/4);
        for (i = 0; i < GEN7_L3LOG_SIZE/4; i++) {
                *cs++ = i915_mmio_reg_offset(GEN7_L3LOG(slice, i));
                *cs++ = remap_info[i];
        }
        *cs++ = MI_NOOP;
        intel_ring_advance(req, cs);

        return 0;
}

static inline bool skip_rcs_switch(struct i915_hw_ppgtt *ppgtt,
                                   struct intel_engine_cs *engine,
                                   struct i915_gem_context *to)
{
        if (to->remap_slice)
                return false;

        if (!to->engine[RCS].initialised)
                return false;

        if (ppgtt && (intel_engine_flag(engine) & ppgtt->pd_dirty_rings))
                return false;

        return to == engine->legacy_active_context;
}

static bool
needs_pd_load_pre(struct i915_hw_ppgtt *ppgtt, struct intel_engine_cs *engine)
{
        struct i915_gem_context *from = engine->legacy_active_context;

        if (!ppgtt)
                return false;

        /* Always load the ppgtt on first use */
        if (!from)
                return true;

        /* Same context without new entries, skip */
        if ((!from->ppgtt || from->ppgtt == ppgtt) &&
            !(intel_engine_flag(engine) & ppgtt->pd_dirty_rings))
                return false;

        if (engine->id != RCS)
                return true;

        if (INTEL_GEN(engine->i915) < 8)
                return true;

        return false;
}

static bool
needs_pd_load_post(struct i915_hw_ppgtt *ppgtt,
                   struct i915_gem_context *to,
                   u32 hw_flags)
{
        if (!ppgtt)
                return false;

        if (!IS_GEN8(to->i915))
                return false;

        if (hw_flags & MI_RESTORE_INHIBIT)
                return true;

        return false;
}

static int do_rcs_switch(struct drm_i915_gem_request *req)
{
        struct i915_gem_context *to = req->ctx;
        struct intel_engine_cs *engine = req->engine;
        struct i915_hw_ppgtt *ppgtt = to->ppgtt ?: req->i915->mm.aliasing_ppgtt;
        struct i915_gem_context *from = engine->legacy_active_context;
        u32 hw_flags;
        int ret, i;

        GEM_BUG_ON(engine->id != RCS);

        if (skip_rcs_switch(ppgtt, engine, to))
                return 0;

        if (needs_pd_load_pre(ppgtt, engine)) {
                /* Older GENs and non render rings still want the load first,
                 * "PP_DCLV followed by PP_DIR_BASE register through Load
                 * Register Immediate commands in Ring Buffer before submitting
                 * a context."*/
                trace_switch_mm(engine, to);
                ret = ppgtt->switch_mm(ppgtt, req);
                if (ret)
                        return ret;
        }

        if (!to->engine[RCS].initialised || i915_gem_context_is_default(to))
                /* NB: If we inhibit the restore, the context is not allowed to
                 * die because future work may end up depending on valid address
                 * space. This means we must enforce that a page table load
                 * occur when this occurs. */
                hw_flags = MI_RESTORE_INHIBIT;
        else if (ppgtt && intel_engine_flag(engine) & ppgtt->pd_dirty_rings)
                hw_flags = MI_FORCE_RESTORE;
        else
                hw_flags = 0;

        if (to != from || (hw_flags & MI_FORCE_RESTORE)) {
                ret = mi_set_context(req, hw_flags);
                if (ret)
                        return ret;

                engine->legacy_active_context = to;
        }

        /* GEN8 does *not* require an explicit reload if the PDPs have been
         * setup, and we do not wish to move them.
         */
        if (needs_pd_load_post(ppgtt, to, hw_flags)) {
                trace_switch_mm(engine, to);
                ret = ppgtt->switch_mm(ppgtt, req);
                /* The hardware context switch is emitted, but we haven't
                 * actually changed the state - so it's probably safe to bail
                 * here. Still, let the user know something dangerous has
                 * happened.
                 */
                if (ret)
                        return ret;
        }

        if (ppgtt)
                ppgtt->pd_dirty_rings &= ~intel_engine_flag(engine);

        for (i = 0; i < MAX_L3_SLICES; i++) {
                if (!(to->remap_slice & (1<<i)))
                        continue;

                ret = remap_l3(req, i);
                if (ret)
                        return ret;

                to->remap_slice &= ~(1<<i);
        }

        if (!to->engine[RCS].initialised) {
                if (engine->init_context) {
                        ret = engine->init_context(req);
                        if (ret)
                                return ret;
                }
                to->engine[RCS].initialised = true;
        }

        return 0;
}

/**
 * i915_switch_context() - perform a GPU context switch.
 * @req: request for which we'll execute the context switch
 *
 * The context life cycle is simple. The context refcount is incremented and
 * decremented by 1 and create and destroy. If the context is in use by the GPU,
 * it will have a refcount > 1. This allows us to destroy the context abstract
 * object while letting the normal object tracking destroy the backing BO.
 *
 * This function should not be used in execlists mode.  Instead the context is
 * switched by writing to the ELSP and requests keep a reference to their
 * context.
 */
int i915_switch_context(struct drm_i915_gem_request *req)
{
        struct intel_engine_cs *engine = req->engine;

        lockdep_assert_held(&req->i915->drm.struct_mutex);
        if (i915.enable_execlists)
                return 0;

        if (!req->ctx->engine[engine->id].state) {
                struct i915_gem_context *to = req->ctx;
                struct i915_hw_ppgtt *ppgtt =
                        to->ppgtt ?: req->i915->mm.aliasing_ppgtt;

                if (needs_pd_load_pre(ppgtt, engine)) {
                        int ret;

                        trace_switch_mm(engine, to);
                        ret = ppgtt->switch_mm(ppgtt, req);
                        if (ret)
                                return ret;

                        ppgtt->pd_dirty_rings &= ~intel_engine_flag(engine);
                }

                engine->legacy_active_context = to;
                return 0;
        }

        return do_rcs_switch(req);
}

static bool engine_has_kernel_context(struct intel_engine_cs *engine)
{
        struct i915_gem_timeline *timeline;

        list_for_each_entry(timeline, &engine->i915->gt.timelines, link) {
                struct intel_timeline *tl;

                if (timeline == &engine->i915->gt.global_timeline)
                        continue;

                tl = &timeline->engine[engine->id];
                if (i915_gem_active_peek(&tl->last_request,
                                         &engine->i915->drm.struct_mutex))
                        return false;
        }

        return (!engine->last_retired_context ||
                i915_gem_context_is_kernel(engine->last_retired_context));
}

int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
{
        struct intel_engine_cs *engine;
        struct i915_gem_timeline *timeline;
        enum intel_engine_id id;

        lockdep_assert_held(&dev_priv->drm.struct_mutex);

        i915_gem_retire_requests(dev_priv);

        for_each_engine(engine, dev_priv, id) {
                struct drm_i915_gem_request *req;
                int ret;

                if (engine_has_kernel_context(engine))
                        continue;

                req = i915_gem_request_alloc(engine, dev_priv->kernel_context);
                if (IS_ERR(req))
                        return PTR_ERR(req);

                /* Queue this switch after all other activity */
                list_for_each_entry(timeline, &dev_priv->gt.timelines, link) {
                        struct drm_i915_gem_request *prev;
                        struct intel_timeline *tl;

                        tl = &timeline->engine[engine->id];
                        prev = i915_gem_active_raw(&tl->last_request,
                                                   &dev_priv->drm.struct_mutex);
                        if (prev)
                                i915_sw_fence_await_sw_fence_gfp(&req->submit,
                                                                 &prev->submit,
                                                                 GFP_KERNEL);
                }

                ret = i915_switch_context(req);
                i915_add_request(req);
                if (ret)
                        return ret;
        }

        return 0;
}

static bool client_is_banned(struct drm_i915_file_private *file_priv)
{
        return atomic_read(&file_priv->context_bans) > I915_MAX_CLIENT_CONTEXT_BANS;
}

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 (!dev_priv->engine[RCS]->context_size)
                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 = ctx->flags & CONTEXT_NO_ZEROMAP;
                break;
        case I915_CONTEXT_PARAM_GTT_SIZE:
                if (ctx->ppgtt)
                        args->value = ctx->ppgtt->base.total;
                else if (to_i915(dev)->mm.aliasing_ppgtt)
                        args->value = to_i915(dev)->mm.aliasing_ppgtt->base.total;
                else
                        args->value = to_i915(dev)->ggtt.base.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;
        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;

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

        ret = i915_mutex_lock_interruptible(dev);
        if (ret)
                goto out;

        switch (args->param) {
        case I915_CONTEXT_PARAM_BAN_PERIOD:
                ret = -EINVAL;
                break;
        case I915_CONTEXT_PARAM_NO_ZEROMAP:
                if (args->size) {
                        ret = -EINVAL;
                } else {
                        ctx->flags &= ~CONTEXT_NO_ZEROMAP;
                        ctx->flags |= args->value ? CONTEXT_NO_ZEROMAP : 0;
                }
                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;
        default:
                ret = -EINVAL;
                break;
        }
        mutex_unlock(&dev->struct_mutex);

out:
        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;
}

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