drivers/gpu/drm/i915/i915_gem_context.c - kernel/msm-4.19 - Gitiles

 /*
  * 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 <drm/drmP.h>
 #include <drm/i915_drm.h>
 #include "i915_drv.h"

 /* This is a HW constraint. The value below is the largest known requirement
  * I've seen in a spec to date, and that was a workaround for a non-shipping
  * part. It should be safe to decrease this, but it's more future proof as is.
  */
 #define CONTEXT_ALIGN (64<<10)

 static struct i915_hw_context *
 i915_gem_context_get(struct drm_i915_file_private *file_priv, u32 id);
 static int do_switch(struct i915_hw_context *to);

 static int get_context_size(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret;
 	u32 reg;

 	switch (INTEL_INFO(dev)->gen) {
 	case 6:
 		reg = I915_READ(CXT_SIZE);
 		ret = GEN6_CXT_TOTAL_SIZE(reg) * 64;
 		break;
 	case 7:
 		reg = I915_READ(GEN7_CXT_SIZE);
 		if (IS_HASWELL(dev))
 			ret = HSW_CXT_TOTAL_SIZE;
 		else
 			ret = GEN7_CXT_TOTAL_SIZE(reg) * 64;
 		break;
 	case 8:
 		ret = GEN8_CXT_TOTAL_SIZE;
 		break;
 	default:
 		BUG();
 	}

 	return ret;
 }

 void i915_gem_context_free(struct kref *ctx_ref)
 {
 	struct i915_hw_context *ctx = container_of(ctx_ref,
 						   typeof(*ctx), ref);

 	list_del(&ctx->link);
 	drm_gem_object_unreference(&ctx->obj->base);
 	kfree(ctx);
 }

 static struct i915_hw_context *
 create_hw_context(struct drm_device *dev,
 		  struct drm_i915_file_private *file_priv)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct i915_hw_context *ctx;
 	int ret;

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

 	kref_init(&ctx->ref);
 	ctx->obj = i915_gem_alloc_object(dev, dev_priv->hw_context_size);
 	INIT_LIST_HEAD(&ctx->link);
 	if (ctx->obj == NULL) {
 		kfree(ctx);
 		DRM_DEBUG_DRIVER("Context object allocated failed\n");
 		return ERR_PTR(-ENOMEM);
 	}

 	if (INTEL_INFO(dev)->gen >= 7) {
 		ret = i915_gem_object_set_cache_level(ctx->obj,
 						      I915_CACHE_L3_LLC);
 		/* Failure shouldn't ever happen this early */
 		if (WARN_ON(ret))
 			goto err_out;
 	}

 	/* The ring associated with the context object is handled by the normal
 	 * object tracking code. We give an initial ring value simple to pass an
 	 * assertion in the context switch code.
 	 */
 	ctx->ring = &dev_priv->ring[RCS];
 	list_add_tail(&ctx->link, &dev_priv->context_list);

 	/* Default context will never have a file_priv */
 	if (file_priv == NULL)
 		return ctx;

 	ret = idr_alloc(&file_priv->context_idr, ctx, DEFAULT_CONTEXT_ID + 1, 0,
 			GFP_KERNEL);
 	if (ret < 0)
 		goto err_out;

 	ctx->file_priv = file_priv;
 	ctx->id = ret;
 	/* 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 = (1 << NUM_L3_SLICES(dev)) - 1;

 	return ctx;

 err_out:
 	i915_gem_context_unreference(ctx);
 	return ERR_PTR(ret);
 }

 static inline bool is_default_context(struct i915_hw_context *ctx)
 {
 	return (ctx == ctx->ring->default_context);
 }

 /**
  * 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 int create_default_context(struct drm_i915_private *dev_priv)
 {
 	struct i915_hw_context *ctx;
 	int ret;

 	BUG_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));

 	ctx = create_hw_context(dev_priv->dev, NULL);
 	if (IS_ERR(ctx))
 		return PTR_ERR(ctx);

 	/* We may need to do things with the shrinker which require us to
 	 * immediately switch back to the default context. This can cause a
 	 * problem as pinning the default context also requires GTT space which
 	 * may not be available. To avoid this we always pin the
 	 * default context.
 	 */
 	ret = i915_gem_obj_ggtt_pin(ctx->obj, CONTEXT_ALIGN, false, false);
 	if (ret) {
 		DRM_DEBUG_DRIVER("Couldn't pin %d\n", ret);
 		goto err_destroy;
 	}

 	ret = do_switch(ctx);
 	if (ret) {
 		DRM_DEBUG_DRIVER("Switch failed %d\n", ret);
 		goto err_unpin;
 	}

 	dev_priv->ring[RCS].default_context = ctx;

 	DRM_DEBUG_DRIVER("Default HW context loaded\n");
 	return 0;

 err_unpin:
 	i915_gem_object_unpin(ctx->obj);
 err_destroy:
 	i915_gem_context_unreference(ctx);
 	return ret;
 }

 int i915_gem_context_init(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret;

 	if (!HAS_HW_CONTEXTS(dev))
 		return 0;

 	/* If called from reset, or thaw... we've been here already */
 	if (dev_priv->ring[RCS].default_context)
 		return 0;

 	dev_priv->hw_context_size = round_up(get_context_size(dev), 4096);

 	if (dev_priv->hw_context_size > (1<<20)) {
 		DRM_DEBUG_DRIVER("Disabling HW Contexts; invalid size\n");
 		return -E2BIG;
 	}

 	ret = create_default_context(dev_priv);
 	if (ret) {
 		DRM_DEBUG_DRIVER("Disabling HW Contexts; create failed %d\n",
 				 ret);
 		return ret;
 	}

 	DRM_DEBUG_DRIVER("HW context support initialized\n");
 	return 0;
 }

 void i915_gem_context_fini(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct i915_hw_context *dctx = dev_priv->ring[RCS].default_context;

 	if (!HAS_HW_CONTEXTS(dev))
 		return;

 	/* The only known way to stop the gpu from accessing the hw context is
 	 * to reset it. Do this as the very last operation to avoid confusing
 	 * other code, leading to spurious errors. */
 	intel_gpu_reset(dev);

 	/* When default context is created and switched to, base object refcount
 	 * will be 2 (+1 from object creation and +1 from do_switch()).
 	 * i915_gem_context_fini() will be called after gpu_idle() has switched
 	 * to default context. So we need to unreference the base object once
 	 * to offset the do_switch part, so that i915_gem_context_unreference()
 	 * can then free the base object correctly. */
 	WARN_ON(!dev_priv->ring[RCS].last_context);
 	if (dev_priv->ring[RCS].last_context == dctx) {
 		/* Fake switch to NULL context */
 		WARN_ON(dctx->obj->active);
 		i915_gem_object_unpin(dctx->obj);
 		i915_gem_context_unreference(dctx);
 	}

 	i915_gem_object_unpin(dctx->obj);
 	i915_gem_context_unreference(dctx);
 	dev_priv->ring[RCS].default_context = NULL;
 	dev_priv->ring[RCS].last_context = NULL;
 }

 static int context_idr_cleanup(int id, void *p, void *data)
 {
 	struct i915_hw_context *ctx = p;

 	BUG_ON(id == DEFAULT_CONTEXT_ID);

 	i915_gem_context_unreference(ctx);
 	return 0;
 }

 struct i915_ctx_hang_stats *
 i915_gem_context_get_hang_stats(struct drm_device *dev,
 				struct drm_file *file,
 				u32 id)
 {
 	struct drm_i915_file_private *file_priv = file->driver_priv;
 	struct i915_hw_context *ctx;

 	if (id == DEFAULT_CONTEXT_ID)
 		return &file_priv->hang_stats;

 	if (!HAS_HW_CONTEXTS(dev))
 		return ERR_PTR(-ENOENT);

 	ctx = i915_gem_context_get(file->driver_priv, id);
 	if (ctx == NULL)
 		return ERR_PTR(-ENOENT);

 	return &ctx->hang_stats;
 }

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

 	mutex_lock(&dev->struct_mutex);
 	idr_for_each(&file_priv->context_idr, context_idr_cleanup, NULL);
 	idr_destroy(&file_priv->context_idr);
 	mutex_unlock(&dev->struct_mutex);
 }

 static struct i915_hw_context *
 i915_gem_context_get(struct drm_i915_file_private *file_priv, u32 id)
 {
 	return (struct i915_hw_context *)idr_find(&file_priv->context_idr, id);
 }

 static inline int
 mi_set_context(struct intel_ring_buffer *ring,
 	       struct i915_hw_context *new_context,
 	       u32 hw_flags)
 {
 	int ret;

 	/* w/a: If Flush TLB Invalidation Mode is enabled, driver must do a TLB
 	 * invalidation prior to MI_SET_CONTEXT. On GEN6 we don't set the value
 	 * explicitly, so we rely on the value at ring init, stored in
 	 * itlb_before_ctx_switch.
 	 */
 	if (IS_GEN6(ring->dev) && ring->itlb_before_ctx_switch) {
 		ret = ring->flush(ring, I915_GEM_GPU_DOMAINS, 0);
 		if (ret)
 			return ret;
 	}

 	ret = intel_ring_begin(ring, 6);
 	if (ret)
 		return ret;

 	/* WaProgramMiArbOnOffAroundMiSetContext:ivb,vlv,hsw */
 	if (IS_GEN7(ring->dev))
 		intel_ring_emit(ring, MI_ARB_ON_OFF | MI_ARB_DISABLE);
 	else
 		intel_ring_emit(ring, MI_NOOP);

 	intel_ring_emit(ring, MI_NOOP);
 	intel_ring_emit(ring, MI_SET_CONTEXT);
 	intel_ring_emit(ring, i915_gem_obj_ggtt_offset(new_context->obj) |
 			MI_MM_SPACE_GTT |
 			MI_SAVE_EXT_STATE_EN |
 			MI_RESTORE_EXT_STATE_EN |
 			hw_flags);
 	/* w/a: MI_SET_CONTEXT must always be followed by MI_NOOP */
 	intel_ring_emit(ring, MI_NOOP);

 	if (IS_GEN7(ring->dev))
 		intel_ring_emit(ring, MI_ARB_ON_OFF | MI_ARB_ENABLE);
 	else
 		intel_ring_emit(ring, MI_NOOP);

 	intel_ring_advance(ring);

 	return ret;
 }

 static int do_switch(struct i915_hw_context *to)
 {
 	struct intel_ring_buffer *ring = to->ring;
 	struct i915_hw_context *from = ring->last_context;
 	u32 hw_flags = 0;
 	int ret, i;

 	BUG_ON(from != NULL && from->obj != NULL && from->obj->pin_count == 0);

 	if (from == to && !to->remap_slice)
 		return 0;

 	ret = i915_gem_obj_ggtt_pin(to->obj, CONTEXT_ALIGN, false, false);
 	if (ret)
 		return ret;

 	/* Clear this page out of any CPU caches for coherent swap-in/out. Note
 	 * that thanks to write = false in this call and us not setting any gpu
 	 * write domains when putting a context object onto the active list
 	 * (when switching away from it), this won't block.
 	 * XXX: We need a real interface to do this instead of trickery. */
 	ret = i915_gem_object_set_to_gtt_domain(to->obj, false);
 	if (ret) {
 		i915_gem_object_unpin(to->obj);
 		return ret;
 	}

 	if (!to->obj->has_global_gtt_mapping)
 		i915_gem_gtt_bind_object(to->obj, to->obj->cache_level);

 	if (!to->is_initialized || is_default_context(to))
 		hw_flags |= MI_RESTORE_INHIBIT;

 	ret = mi_set_context(ring, to, hw_flags);
 	if (ret) {
 		i915_gem_object_unpin(to->obj);
 		return ret;
 	}

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

 		ret = i915_gem_l3_remap(ring, i);
 		/* If it failed, try again next round */
 		if (ret)
 			DRM_DEBUG_DRIVER("L3 remapping failed\n");
 		else
 			to->remap_slice &= ~(1<<i);
 	}

 	/* The backing object for the context is done after switching to the
 	 * *next* context. Therefore we cannot retire the previous context until
 	 * the next context has already started running. In fact, the below code
 	 * is a bit suboptimal because the retiring can occur simply after the
 	 * MI_SET_CONTEXT instead of when the next seqno has completed.
 	 */
 	if (from != NULL) {
 		from->obj->base.read_domains = I915_GEM_DOMAIN_INSTRUCTION;
 		i915_vma_move_to_active(i915_gem_obj_to_ggtt(from->obj), ring);
 		/* As long as MI_SET_CONTEXT is serializing, ie. it flushes the
 		 * whole damn pipeline, we don't need to explicitly mark the
 		 * object dirty. The only exception is that the context must be
 		 * correct in case the object gets swapped out. Ideally we'd be
 		 * able to defer doing this until we know the object would be
 		 * swapped, but there is no way to do that yet.
 		 */
 		from->obj->dirty = 1;
 		BUG_ON(from->obj->ring != ring);

 		/* obj is kept alive until the next request by its active ref */
 		i915_gem_object_unpin(from->obj);
 		i915_gem_context_unreference(from);
 	}

 	i915_gem_context_reference(to);
 	ring->last_context = to;
 	to->is_initialized = true;

 	return 0;
 }

 /**
  * i915_switch_context() - perform a GPU context switch.
  * @ring: ring for which we'll execute the context switch
  * @file_priv: file_priv associated with the context, may be NULL
  * @id: context id number
  *
  * 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 refoucnt > 1. This allows us to destroy the context abstract
  * object while letting the normal object tracking destroy the backing BO.
  */
 int i915_switch_context(struct intel_ring_buffer *ring,
 			struct drm_file *file,
 			int to_id)
 {
 	struct drm_i915_private *dev_priv = ring->dev->dev_private;
 	struct i915_hw_context *to;

 	if (!HAS_HW_CONTEXTS(ring->dev))
 		return 0;

 	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));

 	if (ring != &dev_priv->ring[RCS])
 		return 0;

 	if (to_id == DEFAULT_CONTEXT_ID) {
 		to = ring->default_context;
 	} else {
 		if (file == NULL)
 			return -EINVAL;

 		to = i915_gem_context_get(file->driver_priv, to_id);
 		if (to == NULL)
 			return -ENOENT;
 	}

 	return do_switch(to);
 }

 int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
 				  struct drm_file *file)
 {
 	struct drm_i915_gem_context_create *args = data;
 	struct drm_i915_file_private *file_priv = file->driver_priv;
 	struct i915_hw_context *ctx;
 	int ret;

 	if (!(dev->driver->driver_features & DRIVER_GEM))
 		return -ENODEV;

 	if (!HAS_HW_CONTEXTS(dev))
 		return -ENODEV;

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

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

 	args->ctx_id = ctx->id;
 	DRM_DEBUG_DRIVER("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_hw_context *ctx;
 	int ret;

 	if (!(dev->driver->driver_features & DRIVER_GEM))
 		return -ENODEV;

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

 	ctx = i915_gem_context_get(file_priv, args->ctx_id);
 	if (!ctx) {
 		mutex_unlock(&dev->struct_mutex);
 		return -ENOENT;
 	}

 	idr_remove(&ctx->file_priv->context_idr, ctx->id);
 	i915_gem_context_unreference(ctx);
 	mutex_unlock(&dev->struct_mutex);

 	DRM_DEBUG_DRIVER("HW context %d destroyed\n", args->ctx_id);
 	return 0;
 }
	/*
	* 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 <drm/drmP.h>
	#include <drm/i915_drm.h>
	#include "i915_drv.h"

	/* This is a HW constraint. The value below is the largest known requirement
	* I've seen in a spec to date, and that was a workaround for a non-shipping
	* part. It should be safe to decrease this, but it's more future proof as is.
	*/
	#define CONTEXT_ALIGN (64<<10)

	static struct i915_hw_context *
	i915_gem_context_get(struct drm_i915_file_private *file_priv, u32 id);
	static int do_switch(struct i915_hw_context *to);

	static int get_context_size(struct drm_device *dev)
	{
	struct drm_i915_private *dev_priv = dev->dev_private;
	int ret;
	u32 reg;

	switch (INTEL_INFO(dev)->gen) {
	case 6:
	reg = I915_READ(CXT_SIZE);
	ret = GEN6_CXT_TOTAL_SIZE(reg) * 64;
	break;
	case 7:
	reg = I915_READ(GEN7_CXT_SIZE);
	if (IS_HASWELL(dev))
	ret = HSW_CXT_TOTAL_SIZE;
	else
	ret = GEN7_CXT_TOTAL_SIZE(reg) * 64;
	break;
	case 8:
	ret = GEN8_CXT_TOTAL_SIZE;
	break;
	default:
	BUG();
	}

	return ret;
	}

	void i915_gem_context_free(struct kref *ctx_ref)
	{
	struct i915_hw_context *ctx = container_of(ctx_ref,
	typeof(*ctx), ref);

	list_del(&ctx->link);
	drm_gem_object_unreference(&ctx->obj->base);
	kfree(ctx);
	}

	static struct i915_hw_context *
	create_hw_context(struct drm_device *dev,
	struct drm_i915_file_private *file_priv)
	{
	struct drm_i915_private *dev_priv = dev->dev_private;
	struct i915_hw_context *ctx;
	int ret;

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

	kref_init(&ctx->ref);
	ctx->obj = i915_gem_alloc_object(dev, dev_priv->hw_context_size);
	INIT_LIST_HEAD(&ctx->link);
	if (ctx->obj == NULL) {
	kfree(ctx);
	DRM_DEBUG_DRIVER("Context object allocated failed\n");
	return ERR_PTR(-ENOMEM);
	}

	if (INTEL_INFO(dev)->gen >= 7) {
	ret = i915_gem_object_set_cache_level(ctx->obj,
	I915_CACHE_L3_LLC);
	/* Failure shouldn't ever happen this early */
	if (WARN_ON(ret))
	goto err_out;
	}

	/* The ring associated with the context object is handled by the normal
	* object tracking code. We give an initial ring value simple to pass an
	* assertion in the context switch code.
	*/
	ctx->ring = &dev_priv->ring[RCS];
	list_add_tail(&ctx->link, &dev_priv->context_list);

	/* Default context will never have a file_priv */
	if (file_priv == NULL)
	return ctx;

	ret = idr_alloc(&file_priv->context_idr, ctx, DEFAULT_CONTEXT_ID + 1, 0,
	GFP_KERNEL);
	if (ret < 0)
	goto err_out;

	ctx->file_priv = file_priv;
	ctx->id = ret;
	/* 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 = (1 << NUM_L3_SLICES(dev)) - 1;

	return ctx;

	err_out:
	i915_gem_context_unreference(ctx);
	return ERR_PTR(ret);
	}

	static inline bool is_default_context(struct i915_hw_context *ctx)
	{
	return (ctx == ctx->ring->default_context);
	}

	/**
	* 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 int create_default_context(struct drm_i915_private *dev_priv)
	{
	struct i915_hw_context *ctx;
	int ret;

	BUG_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));

	ctx = create_hw_context(dev_priv->dev, NULL);
	if (IS_ERR(ctx))
	return PTR_ERR(ctx);

	/* We may need to do things with the shrinker which require us to
	* immediately switch back to the default context. This can cause a
	* problem as pinning the default context also requires GTT space which
	* may not be available. To avoid this we always pin the
	* default context.
	*/
	ret = i915_gem_obj_ggtt_pin(ctx->obj, CONTEXT_ALIGN, false, false);
	if (ret) {
	DRM_DEBUG_DRIVER("Couldn't pin %d\n", ret);
	goto err_destroy;
	}

	ret = do_switch(ctx);
	if (ret) {
	DRM_DEBUG_DRIVER("Switch failed %d\n", ret);
	goto err_unpin;
	}

	dev_priv->ring[RCS].default_context = ctx;

	DRM_DEBUG_DRIVER("Default HW context loaded\n");
	return 0;

	err_unpin:
	i915_gem_object_unpin(ctx->obj);
	err_destroy:
	i915_gem_context_unreference(ctx);
	return ret;
	}

	int i915_gem_context_init(struct drm_device *dev)
	{
	struct drm_i915_private *dev_priv = dev->dev_private;
	int ret;

	if (!HAS_HW_CONTEXTS(dev))
	return 0;

	/* If called from reset, or thaw... we've been here already */
	if (dev_priv->ring[RCS].default_context)
	return 0;

	dev_priv->hw_context_size = round_up(get_context_size(dev), 4096);

	if (dev_priv->hw_context_size > (1<<20)) {
	DRM_DEBUG_DRIVER("Disabling HW Contexts; invalid size\n");
	return -E2BIG;
	}

	ret = create_default_context(dev_priv);
	if (ret) {
	DRM_DEBUG_DRIVER("Disabling HW Contexts; create failed %d\n",
	ret);
	return ret;
	}

	DRM_DEBUG_DRIVER("HW context support initialized\n");
	return 0;
	}

	void i915_gem_context_fini(struct drm_device *dev)
	{
	struct drm_i915_private *dev_priv = dev->dev_private;
	struct i915_hw_context *dctx = dev_priv->ring[RCS].default_context;

	if (!HAS_HW_CONTEXTS(dev))
	return;

	/* The only known way to stop the gpu from accessing the hw context is
	* to reset it. Do this as the very last operation to avoid confusing
	* other code, leading to spurious errors. */
	intel_gpu_reset(dev);

	/* When default context is created and switched to, base object refcount
	* will be 2 (+1 from object creation and +1 from do_switch()).
	* i915_gem_context_fini() will be called after gpu_idle() has switched
	* to default context. So we need to unreference the base object once
	* to offset the do_switch part, so that i915_gem_context_unreference()
	* can then free the base object correctly. */
	WARN_ON(!dev_priv->ring[RCS].last_context);
	if (dev_priv->ring[RCS].last_context == dctx) {
	/* Fake switch to NULL context */
	WARN_ON(dctx->obj->active);
	i915_gem_object_unpin(dctx->obj);
	i915_gem_context_unreference(dctx);
	}

	i915_gem_object_unpin(dctx->obj);
	i915_gem_context_unreference(dctx);
	dev_priv->ring[RCS].default_context = NULL;
	dev_priv->ring[RCS].last_context = NULL;
	}

	static int context_idr_cleanup(int id, void p, void data)
	{
	struct i915_hw_context *ctx = p;

	BUG_ON(id == DEFAULT_CONTEXT_ID);

	i915_gem_context_unreference(ctx);
	return 0;
	}

	struct i915_ctx_hang_stats *
	i915_gem_context_get_hang_stats(struct drm_device *dev,
	struct drm_file *file,
	u32 id)
	{
	struct drm_i915_file_private *file_priv = file->driver_priv;
	struct i915_hw_context *ctx;

	if (id == DEFAULT_CONTEXT_ID)
	return &file_priv->hang_stats;

	if (!HAS_HW_CONTEXTS(dev))
	return ERR_PTR(-ENOENT);

	ctx = i915_gem_context_get(file->driver_priv, id);
	if (ctx == NULL)
	return ERR_PTR(-ENOENT);

	return &ctx->hang_stats;
	}

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

	mutex_lock(&dev->struct_mutex);
	idr_for_each(&file_priv->context_idr, context_idr_cleanup, NULL);
	idr_destroy(&file_priv->context_idr);
	mutex_unlock(&dev->struct_mutex);
	}

	static struct i915_hw_context *
	i915_gem_context_get(struct drm_i915_file_private *file_priv, u32 id)
	{
	return (struct i915_hw_context *)idr_find(&file_priv->context_idr, id);
	}

	static inline int
	mi_set_context(struct intel_ring_buffer *ring,
	struct i915_hw_context *new_context,
	u32 hw_flags)
	{
	int ret;

	/* w/a: If Flush TLB Invalidation Mode is enabled, driver must do a TLB
	* invalidation prior to MI_SET_CONTEXT. On GEN6 we don't set the value
	* explicitly, so we rely on the value at ring init, stored in
	* itlb_before_ctx_switch.
	*/
	if (IS_GEN6(ring->dev) && ring->itlb_before_ctx_switch) {
	ret = ring->flush(ring, I915_GEM_GPU_DOMAINS, 0);
	if (ret)
	return ret;
	}

	ret = intel_ring_begin(ring, 6);
	if (ret)
	return ret;

	/* WaProgramMiArbOnOffAroundMiSetContext:ivb,vlv,hsw */
	if (IS_GEN7(ring->dev))
	intel_ring_emit(ring, MI_ARB_ON_OFF \| MI_ARB_DISABLE);
	else
	intel_ring_emit(ring, MI_NOOP);

	intel_ring_emit(ring, MI_NOOP);
	intel_ring_emit(ring, MI_SET_CONTEXT);
	intel_ring_emit(ring, i915_gem_obj_ggtt_offset(new_context->obj) \|
	MI_MM_SPACE_GTT \|
	MI_SAVE_EXT_STATE_EN \|
	MI_RESTORE_EXT_STATE_EN \|
	hw_flags);
	/* w/a: MI_SET_CONTEXT must always be followed by MI_NOOP */
	intel_ring_emit(ring, MI_NOOP);

	if (IS_GEN7(ring->dev))
	intel_ring_emit(ring, MI_ARB_ON_OFF \| MI_ARB_ENABLE);
	else
	intel_ring_emit(ring, MI_NOOP);

	intel_ring_advance(ring);

	return ret;
	}

	static int do_switch(struct i915_hw_context *to)
	{
	struct intel_ring_buffer *ring = to->ring;
	struct i915_hw_context *from = ring->last_context;
	u32 hw_flags = 0;
	int ret, i;

	BUG_ON(from != NULL && from->obj != NULL && from->obj->pin_count == 0);

	if (from == to && !to->remap_slice)
	return 0;

	ret = i915_gem_obj_ggtt_pin(to->obj, CONTEXT_ALIGN, false, false);
	if (ret)
	return ret;

	/* Clear this page out of any CPU caches for coherent swap-in/out. Note
	* that thanks to write = false in this call and us not setting any gpu
	* write domains when putting a context object onto the active list
	* (when switching away from it), this won't block.
	* XXX: We need a real interface to do this instead of trickery. */
	ret = i915_gem_object_set_to_gtt_domain(to->obj, false);
	if (ret) {
	i915_gem_object_unpin(to->obj);
	return ret;
	}

	if (!to->obj->has_global_gtt_mapping)
	i915_gem_gtt_bind_object(to->obj, to->obj->cache_level);

	if (!to->is_initialized \|\| is_default_context(to))
	hw_flags \|= MI_RESTORE_INHIBIT;

	ret = mi_set_context(ring, to, hw_flags);
	if (ret) {
	i915_gem_object_unpin(to->obj);
	return ret;
	}

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

	ret = i915_gem_l3_remap(ring, i);
	/* If it failed, try again next round */
	if (ret)
	DRM_DEBUG_DRIVER("L3 remapping failed\n");
	else
	to->remap_slice &= ~(1<<i);
	}

	/* The backing object for the context is done after switching to the
	* next context. Therefore we cannot retire the previous context until
	* the next context has already started running. In fact, the below code
	* is a bit suboptimal because the retiring can occur simply after the
	* MI_SET_CONTEXT instead of when the next seqno has completed.
	*/
	if (from != NULL) {
	from->obj->base.read_domains = I915_GEM_DOMAIN_INSTRUCTION;
	i915_vma_move_to_active(i915_gem_obj_to_ggtt(from->obj), ring);
	/* As long as MI_SET_CONTEXT is serializing, ie. it flushes the
	* whole damn pipeline, we don't need to explicitly mark the
	* object dirty. The only exception is that the context must be
	* correct in case the object gets swapped out. Ideally we'd be
	* able to defer doing this until we know the object would be
	* swapped, but there is no way to do that yet.
	*/
	from->obj->dirty = 1;
	BUG_ON(from->obj->ring != ring);

	/* obj is kept alive until the next request by its active ref */
	i915_gem_object_unpin(from->obj);
	i915_gem_context_unreference(from);
	}

	i915_gem_context_reference(to);
	ring->last_context = to;
	to->is_initialized = true;

	return 0;
	}

	/**
	* i915_switch_context() - perform a GPU context switch.
	* @ring: ring for which we'll execute the context switch
	* @file_priv: file_priv associated with the context, may be NULL
	* @id: context id number
	*
	* 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 refoucnt > 1. This allows us to destroy the context abstract
	* object while letting the normal object tracking destroy the backing BO.
	*/
	int i915_switch_context(struct intel_ring_buffer *ring,
	struct drm_file *file,
	int to_id)
	{
	struct drm_i915_private *dev_priv = ring->dev->dev_private;
	struct i915_hw_context *to;

	if (!HAS_HW_CONTEXTS(ring->dev))
	return 0;

	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));

	if (ring != &dev_priv->ring[RCS])
	return 0;

	if (to_id == DEFAULT_CONTEXT_ID) {
	to = ring->default_context;
	} else {
	if (file == NULL)
	return -EINVAL;

	to = i915_gem_context_get(file->driver_priv, to_id);
	if (to == NULL)
	return -ENOENT;
	}

	return do_switch(to);
	}

	int i915_gem_context_create_ioctl(struct drm_device dev, void data,
	struct drm_file *file)
	{
	struct drm_i915_gem_context_create *args = data;
	struct drm_i915_file_private *file_priv = file->driver_priv;
	struct i915_hw_context *ctx;
	int ret;

	if (!(dev->driver->driver_features & DRIVER_GEM))
	return -ENODEV;

	if (!HAS_HW_CONTEXTS(dev))
	return -ENODEV;

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

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

	args->ctx_id = ctx->id;
	DRM_DEBUG_DRIVER("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_hw_context *ctx;
	int ret;

	if (!(dev->driver->driver_features & DRIVER_GEM))
	return -ENODEV;

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

	ctx = i915_gem_context_get(file_priv, args->ctx_id);
	if (!ctx) {
	mutex_unlock(&dev->struct_mutex);
	return -ENOENT;
	}

	idr_remove(&ctx->file_priv->context_idr, ctx->id);
	i915_gem_context_unreference(ctx);
	mutex_unlock(&dev->struct_mutex);

	DRM_DEBUG_DRIVER("HW context %d destroyed\n", args->ctx_id);
	return 0;
	}