Initial import

1 files changed, 964 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
new file mode 100644
index 000000000..f3e84c44d
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -0,0 +1,964 @@
+/*
+ * 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"
+#include "i915_trace.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 GEN6_CONTEXT_ALIGN (64<<10)
+#define GEN7_CONTEXT_ALIGN 4096
+
+static size_t get_context_alignment(struct drm_device *dev)
+{
+	if (IS_GEN6(dev))
+		return GEN6_CONTEXT_ALIGN;
+
+	return GEN7_CONTEXT_ALIGN;
+}
+
+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 intel_context *ctx = container_of(ctx_ref,
+						 typeof(*ctx), ref);
+
+	trace_i915_context_free(ctx);
+
+	if (i915.enable_execlists)
+		intel_lr_context_free(ctx);
+
+	i915_ppgtt_put(ctx->ppgtt);
+
+	if (ctx->legacy_hw_ctx.rcs_state)
+		drm_gem_object_unreference(&ctx->legacy_hw_ctx.rcs_state->base);
+	list_del(&ctx->link);
+	kfree(ctx);
+}
+
+struct drm_i915_gem_object *
+i915_gem_alloc_context_obj(struct drm_device *dev, size_t size)
+{
+	struct drm_i915_gem_object *obj;
+	int ret;
+
+	obj = i915_gem_alloc_object(dev, size);
+	if (obj == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	/*
+	 * Try to make the context utilize L3 as well as LLC.
+	 *
+	 * On VLV we don't have L3 controls in the PTEs so we
+	 * shouldn't touch the cache level, especially as that
+	 * would make the object snooped which might have a
+	 * negative performance impact.
+	 */
+	if (INTEL_INFO(dev)->gen >= 7 && !IS_VALLEYVIEW(dev)) {
+		ret = i915_gem_object_set_cache_level(obj, I915_CACHE_L3_LLC);
+		/* Failure shouldn't ever happen this early */
+		if (WARN_ON(ret)) {
+			drm_gem_object_unreference(&obj->base);
+			return ERR_PTR(ret);
+		}
+	}
+
+	return obj;
+}
+
+static struct intel_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 intel_context *ctx;
+	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->context_list);
+
+	if (dev_priv->hw_context_size) {
+		struct drm_i915_gem_object *obj =
+				i915_gem_alloc_context_obj(dev, dev_priv->hw_context_size);
+		if (IS_ERR(obj)) {
+			ret = PTR_ERR(obj);
+			goto err_out;
+		}
+		ctx->legacy_hw_ctx.rcs_state = obj;
+	}
+
+	/* Default context will never have a file_priv */
+	if (file_priv != NULL) {
+		ret = idr_alloc(&file_priv->context_idr, ctx,
+				DEFAULT_CONTEXT_HANDLE, 0, GFP_KERNEL);
+		if (ret < 0)
+			goto err_out;
+	} else
+		ret = DEFAULT_CONTEXT_HANDLE;
+
+	ctx->file_priv = file_priv;
+	ctx->user_handle = 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;
+
+	ctx->hang_stats.ban_period_seconds = DRM_I915_CTX_BAN_PERIOD;
+
+	return ctx;
+
+err_out:
+	i915_gem_context_unreference(ctx);
+	return ERR_PTR(ret);
+}
+
+/**
+ * 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 intel_context *
+i915_gem_create_context(struct drm_device *dev,
+			struct drm_i915_file_private *file_priv)
+{
+	const bool is_global_default_ctx = file_priv == NULL;
+	struct intel_context *ctx;
+	int ret = 0;
+
+	BUG_ON(!mutex_is_locked(&dev->struct_mutex));
+
+	ctx = __create_hw_context(dev, file_priv);
+	if (IS_ERR(ctx))
+		return ctx;
+
+	if (is_global_default_ctx && ctx->legacy_hw_ctx.rcs_state) {
+		/* 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->legacy_hw_ctx.rcs_state,
+					    get_context_alignment(dev), 0);
+		if (ret) {
+			DRM_DEBUG_DRIVER("Couldn't pin %d\n", ret);
+			goto err_destroy;
+		}
+	}
+
+	if (USES_FULL_PPGTT(dev)) {
+		struct i915_hw_ppgtt *ppgtt = i915_ppgtt_create(dev, file_priv);
+
+		if (IS_ERR_OR_NULL(ppgtt)) {
+			DRM_DEBUG_DRIVER("PPGTT setup failed (%ld)\n",
+					 PTR_ERR(ppgtt));
+			ret = PTR_ERR(ppgtt);
+			goto err_unpin;
+		}
+
+		ctx->ppgtt = ppgtt;
+	}
+
+	trace_i915_context_create(ctx);
+
+	return ctx;
+
+err_unpin:
+	if (is_global_default_ctx && ctx->legacy_hw_ctx.rcs_state)
+		i915_gem_object_ggtt_unpin(ctx->legacy_hw_ctx.rcs_state);
+err_destroy:
+	i915_gem_context_unreference(ctx);
+	return ERR_PTR(ret);
+}
+
+void i915_gem_context_reset(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	int i;
+
+	if (i915.enable_execlists) {
+		struct intel_context *ctx;
+
+		list_for_each_entry(ctx, &dev_priv->context_list, link) {
+			intel_lr_context_reset(dev, ctx);
+		}
+
+		return;
+	}
+
+	for (i = 0; i < I915_NUM_RINGS; i++) {
+		struct intel_engine_cs *ring = &dev_priv->ring[i];
+		struct intel_context *lctx = ring->last_context;
+
+		if (lctx) {
+			if (lctx->legacy_hw_ctx.rcs_state && i == RCS)
+				i915_gem_object_ggtt_unpin(lctx->legacy_hw_ctx.rcs_state);
+
+			i915_gem_context_unreference(lctx);
+			ring->last_context = NULL;
+		}
+	}
+}
+
+int i915_gem_context_init(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_context *ctx;
+	int i;
+
+	/* 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->ring[RCS].default_context))
+		return 0;
+
+	if (i915.enable_execlists) {
+		/* NB: intentionally left blank. We will allocate our own
+		 * backing objects as we need them, thank you very much */
+		dev_priv->hw_context_size = 0;
+	} else if (HAS_HW_CONTEXTS(dev)) {
+		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 %d\n",
+					 dev_priv->hw_context_size);
+			dev_priv->hw_context_size = 0;
+		}
+	}
+
+	ctx = i915_gem_create_context(dev, NULL);
+	if (IS_ERR(ctx)) {
+		DRM_ERROR("Failed to create default global context (error %ld)\n",
+			  PTR_ERR(ctx));
+		return PTR_ERR(ctx);
+	}
+
+	for (i = 0; i < I915_NUM_RINGS; i++) {
+		struct intel_engine_cs *ring = &dev_priv->ring[i];
+
+		/* NB: RCS will hold a ref for all rings */
+		ring->default_context = ctx;
+	}
+
+	DRM_DEBUG_DRIVER("%s context support initialized\n",
+			i915.enable_execlists ? "LR" :
+			dev_priv->hw_context_size ? "HW" : "fake");
+	return 0;
+}
+
+void i915_gem_context_fini(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_context *dctx = dev_priv->ring[RCS].default_context;
+	int i;
+
+	if (dctx->legacy_hw_ctx.rcs_state) {
+		/* 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->legacy_hw_ctx.rcs_state->active);
+			i915_gem_object_ggtt_unpin(dctx->legacy_hw_ctx.rcs_state);
+			i915_gem_context_unreference(dctx);
+			dev_priv->ring[RCS].last_context = NULL;
+		}
+
+		i915_gem_object_ggtt_unpin(dctx->legacy_hw_ctx.rcs_state);
+	}
+
+	for (i = 0; i < I915_NUM_RINGS; i++) {
+		struct intel_engine_cs *ring = &dev_priv->ring[i];
+
+		if (ring->last_context)
+			i915_gem_context_unreference(ring->last_context);
+
+		ring->default_context = NULL;
+		ring->last_context = NULL;
+	}
+
+	i915_gem_context_unreference(dctx);
+}
+
+int i915_gem_context_enable(struct drm_i915_private *dev_priv)
+{
+	struct intel_engine_cs *ring;
+	int ret, i;
+
+	BUG_ON(!dev_priv->ring[RCS].default_context);
+
+	if (i915.enable_execlists) {
+		for_each_ring(ring, dev_priv, i) {
+			if (ring->init_context) {
+				ret = ring->init_context(ring,
+						ring->default_context);
+				if (ret) {
+					DRM_ERROR("ring init context: %d\n",
+							ret);
+					return ret;
+				}
+			}
+		}
+
+	} else
+		for_each_ring(ring, dev_priv, i) {
+			ret = i915_switch_context(ring, ring->default_context);
+			if (ret)
+				return ret;
+		}
+
+	return 0;
+}
+
+static int context_idr_cleanup(int id, void *p, void *data)
+{
+	struct intel_context *ctx = p;
+
+	i915_gem_context_unreference(ctx);
+	return 0;
+}
+
+int i915_gem_context_open(struct drm_device *dev, struct drm_file *file)
+{
+	struct drm_i915_file_private *file_priv = file->driver_priv;
+	struct intel_context *ctx;
+
+	idr_init(&file_priv->context_idr);
+
+	mutex_lock(&dev->struct_mutex);
+	ctx = i915_gem_create_context(dev, file_priv);
+	mutex_unlock(&dev->struct_mutex);
+
+	if (IS_ERR(ctx)) {
+		idr_destroy(&file_priv->context_idr);
+		return PTR_ERR(ctx);
+	}
+
+	return 0;
+}
+
+void i915_gem_context_close(struct drm_device *dev, struct drm_file *file)
+{
+	struct drm_i915_file_private *file_priv = file->driver_priv;
+
+	idr_for_each(&file_priv->context_idr, context_idr_cleanup, NULL);
+	idr_destroy(&file_priv->context_idr);
+}
+
+struct intel_context *
+i915_gem_context_get(struct drm_i915_file_private *file_priv, u32 id)
+{
+	struct intel_context *ctx;
+
+	ctx = (struct intel_context *)idr_find(&file_priv->context_idr, id);
+	if (!ctx)
+		return ERR_PTR(-ENOENT);
+
+	return ctx;
+}
+
+static inline int
+mi_set_context(struct intel_engine_cs *ring,
+	       struct intel_context *new_context,
+	       u32 hw_flags)
+{
+	u32 flags = hw_flags | MI_MM_SPACE_GTT;
+	const int num_rings =
+		/* Use an extended w/a on ivb+ if signalling from other rings */
+		i915_semaphore_is_enabled(ring->dev) ?
+		hweight32(INTEL_INFO(ring->dev)->ring_mask) - 1 :
+		0;
+	int len, i, 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)) {
+		ret = ring->flush(ring, I915_GEM_GPU_DOMAINS, 0);
+		if (ret)
+			return ret;
+	}
+
+	/* These flags are for resource streamer on HSW+ */
+	if (!IS_HASWELL(ring->dev) && INTEL_INFO(ring->dev)->gen < 8)
+		flags |= (MI_SAVE_EXT_STATE_EN | MI_RESTORE_EXT_STATE_EN);
+
+
+	len = 4;
+	if (INTEL_INFO(ring->dev)->gen >= 7)
+		len += 2 + (num_rings ? 4*num_rings + 2 : 0);
+
+	ret = intel_ring_begin(ring, len);
+	if (ret)
+		return ret;
+
+	/* WaProgramMiArbOnOffAroundMiSetContext:ivb,vlv,hsw,bdw,chv */
+	if (INTEL_INFO(ring->dev)->gen >= 7) {
+		intel_ring_emit(ring, MI_ARB_ON_OFF | MI_ARB_DISABLE);
+		if (num_rings) {
+			struct intel_engine_cs *signaller;
+
+			intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(num_rings));
+			for_each_ring(signaller, to_i915(ring->dev), i) {
+				if (signaller == ring)
+					continue;
+
+				intel_ring_emit(ring, RING_PSMI_CTL(signaller->mmio_base));
+				intel_ring_emit(ring, _MASKED_BIT_ENABLE(GEN6_PSMI_SLEEP_MSG_DISABLE));
+			}
+		}
+	}
+
+	intel_ring_emit(ring, MI_NOOP);
+	intel_ring_emit(ring, MI_SET_CONTEXT);
+	intel_ring_emit(ring, i915_gem_obj_ggtt_offset(new_context->legacy_hw_ctx.rcs_state) |
+			flags);
+	/*
+	 * w/a: MI_SET_CONTEXT must always be followed by MI_NOOP
+	 * WaMiSetContext_Hang:snb,ivb,vlv
+	 */
+	intel_ring_emit(ring, MI_NOOP);
+
+	if (INTEL_INFO(ring->dev)->gen >= 7) {
+		if (num_rings) {
+			struct intel_engine_cs *signaller;
+
+			intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(num_rings));
+			for_each_ring(signaller, to_i915(ring->dev), i) {
+				if (signaller == ring)
+					continue;
+
+				intel_ring_emit(ring, RING_PSMI_CTL(signaller->mmio_base));
+				intel_ring_emit(ring, _MASKED_BIT_DISABLE(GEN6_PSMI_SLEEP_MSG_DISABLE));
+			}
+		}
+		intel_ring_emit(ring, MI_ARB_ON_OFF | MI_ARB_ENABLE);
+	}
+
+	intel_ring_advance(ring);
+
+	return ret;
+}
+
+static inline bool should_skip_switch(struct intel_engine_cs *ring,
+				      struct intel_context *from,
+				      struct intel_context *to)
+{
+	struct drm_i915_private *dev_priv = ring->dev->dev_private;
+
+	if (to->remap_slice)
+		return false;
+
+	if (to->ppgtt) {
+		if (from == to && !test_bit(ring->id,
+				&to->ppgtt->pd_dirty_rings))
+			return true;
+	} else if (dev_priv->mm.aliasing_ppgtt) {
+		if (from == to && !test_bit(ring->id,
+				&dev_priv->mm.aliasing_ppgtt->pd_dirty_rings))
+			return true;
+	}
+
+	return false;
+}
+
+static bool
+needs_pd_load_pre(struct intel_engine_cs *ring, struct intel_context *to)
+{
+	struct drm_i915_private *dev_priv = ring->dev->dev_private;
+
+	if (!to->ppgtt)
+		return false;
+
+	if (INTEL_INFO(ring->dev)->gen < 8)
+		return true;
+
+	if (ring != &dev_priv->ring[RCS])
+		return true;
+
+	return false;
+}
+
+static bool
+needs_pd_load_post(struct intel_engine_cs *ring, struct intel_context *to,
+		u32 hw_flags)
+{
+	struct drm_i915_private *dev_priv = ring->dev->dev_private;
+
+	if (!to->ppgtt)
+		return false;
+
+	if (!IS_GEN8(ring->dev))
+		return false;
+
+	if (ring != &dev_priv->ring[RCS])
+		return false;
+
+	if (hw_flags & MI_RESTORE_INHIBIT)
+		return true;
+
+	return false;
+}
+
+static int do_switch(struct intel_engine_cs *ring,
+		     struct intel_context *to)
+{
+	struct drm_i915_private *dev_priv = ring->dev->dev_private;
+	struct intel_context *from = ring->last_context;
+	u32 hw_flags = 0;
+	bool uninitialized = false;
+	struct i915_vma *vma;
+	int ret, i;
+
+	if (from != NULL && ring == &dev_priv->ring[RCS]) {
+		BUG_ON(from->legacy_hw_ctx.rcs_state == NULL);
+		BUG_ON(!i915_gem_obj_is_pinned(from->legacy_hw_ctx.rcs_state));
+	}
+
+	if (should_skip_switch(ring, from, to))
+		return 0;
+
+	/* Trying to pin first makes error handling easier. */
+	if (ring == &dev_priv->ring[RCS]) {
+		ret = i915_gem_obj_ggtt_pin(to->legacy_hw_ctx.rcs_state,
+					    get_context_alignment(ring->dev), 0);
+		if (ret)
+			return ret;
+	}
+
+	/*
+	 * Pin can switch back to the default context if we end up calling into
+	 * evict_everything - as a last ditch gtt defrag effort that also
+	 * switches to the default context. Hence we need to reload from here.
+	 */
+	from = ring->last_context;
+
+	if (needs_pd_load_pre(ring, to)) {
+		/* 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(ring, to);
+		ret = to->ppgtt->switch_mm(to->ppgtt, ring);
+		if (ret)
+			goto unpin_out;
+
+		/* Doing a PD load always reloads the page dirs */
+		clear_bit(ring->id, &to->ppgtt->pd_dirty_rings);
+	}
+
+	if (ring != &dev_priv->ring[RCS]) {
+		if (from)
+			i915_gem_context_unreference(from);
+		goto done;
+	}
+
+	/*
+	 * 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->legacy_hw_ctx.rcs_state, false);
+	if (ret)
+		goto unpin_out;
+
+	vma = i915_gem_obj_to_ggtt(to->legacy_hw_ctx.rcs_state);
+	if (!(vma->bound & GLOBAL_BIND)) {
+		ret = i915_vma_bind(vma,
+				    to->legacy_hw_ctx.rcs_state->cache_level,
+				    GLOBAL_BIND);
+		/* This shouldn't ever fail. */
+		if (WARN_ONCE(ret, "GGTT context bind failed!"))
+			goto unpin_out;
+	}
+
+	if (!to->legacy_hw_ctx.initialized) {
+		hw_flags |= MI_RESTORE_INHIBIT;
+		/* 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. */
+	} else if (to->ppgtt &&
+			test_and_clear_bit(ring->id, &to->ppgtt->pd_dirty_rings))
+		hw_flags |= MI_FORCE_RESTORE;
+
+	/* We should never emit switch_mm more than once */
+	WARN_ON(needs_pd_load_pre(ring, to) &&
+			needs_pd_load_post(ring, to, hw_flags));
+
+	ret = mi_set_context(ring, to, hw_flags);
+	if (ret)
+		goto unpin_out;
+
+	/* 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(ring, to, hw_flags)) {
+		trace_switch_mm(ring, to);
+		ret = to->ppgtt->switch_mm(to->ppgtt, ring);
+		/* 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) {
+			DRM_ERROR("Failed to change address space on context switch\n");
+			goto unpin_out;
+		}
+	}
+
+	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->legacy_hw_ctx.rcs_state->base.read_domains = I915_GEM_DOMAIN_INSTRUCTION;
+		i915_vma_move_to_active(i915_gem_obj_to_ggtt(from->legacy_hw_ctx.rcs_state), 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->legacy_hw_ctx.rcs_state->dirty = 1;
+		BUG_ON(i915_gem_request_get_ring(
+			from->legacy_hw_ctx.rcs_state->last_read_req) != ring);
+
+		/* obj is kept alive until the next request by its active ref */
+		i915_gem_object_ggtt_unpin(from->legacy_hw_ctx.rcs_state);
+		i915_gem_context_unreference(from);
+	}
+
+	uninitialized = !to->legacy_hw_ctx.initialized;
+	to->legacy_hw_ctx.initialized = true;
+
+done:
+	i915_gem_context_reference(to);
+	ring->last_context = to;
+
+	if (uninitialized) {
+		if (ring->init_context) {
+			ret = ring->init_context(ring, to);
+			if (ret)
+				DRM_ERROR("ring init context: %d\n", ret);
+		}
+	}
+
+	return 0;
+
+unpin_out:
+	if (ring->id == RCS)
+		i915_gem_object_ggtt_unpin(to->legacy_hw_ctx.rcs_state);
+	return ret;
+}
+
+/**
+ * i915_switch_context() - perform a GPU context switch.
+ * @ring: ring for which we'll execute the context switch
+ * @to: the context to switch to
+ *
+ * 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 intel_engine_cs *ring,
+			struct intel_context *to)
+{
+	struct drm_i915_private *dev_priv = ring->dev->dev_private;
+
+	WARN_ON(i915.enable_execlists);
+	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
+
+	if (to->legacy_hw_ctx.rcs_state == NULL) { /* We have the fake context */
+		if (to != ring->last_context) {
+			i915_gem_context_reference(to);
+			if (ring->last_context)
+				i915_gem_context_unreference(ring->last_context);
+			ring->last_context = to;
+		}
+		return 0;
+	}
+
+	return do_switch(ring, to);
+}
+
+static bool contexts_enabled(struct drm_device *dev)
+{
+	return i915.enable_execlists || to_i915(dev)->hw_context_size;
+}
+
+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 intel_context *ctx;
+	int ret;
+
+	if (!contexts_enabled(dev))
+		return -ENODEV;
+
+	ret = i915_mutex_lock_interruptible(dev);
+	if (ret)
+		return ret;
+
+	ctx = i915_gem_create_context(dev, file_priv);
+	mutex_unlock(&dev->struct_mutex);
+	if (IS_ERR(ctx))
+		return PTR_ERR(ctx);
+
+	args->ctx_id = ctx->user_handle;
+	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 intel_context *ctx;
+	int ret;
+
+	if (args->ctx_id == DEFAULT_CONTEXT_HANDLE)
+		return -ENOENT;
+
+	ret = i915_mutex_lock_interruptible(dev);
+	if (ret)
+		return ret;
+
+	ctx = i915_gem_context_get(file_priv, args->ctx_id);
+	if (IS_ERR(ctx)) {
+		mutex_unlock(&dev->struct_mutex);
+		return PTR_ERR(ctx);
+	}
+
+	idr_remove(&ctx->file_priv->context_idr, ctx->user_handle);
+	i915_gem_context_unreference(ctx);
+	mutex_unlock(&dev->struct_mutex);
+
+	DRM_DEBUG_DRIVER("HW context %d destroyed\n", args->ctx_id);
+	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 intel_context *ctx;
+	int ret;
+
+	ret = i915_mutex_lock_interruptible(dev);
+	if (ret)
+		return ret;
+
+	ctx = i915_gem_context_get(file_priv, args->ctx_id);
+	if (IS_ERR(ctx)) {
+		mutex_unlock(&dev->struct_mutex);
+		return PTR_ERR(ctx);
+	}
+
+	args->size = 0;
+	switch (args->param) {
+	case I915_CONTEXT_PARAM_BAN_PERIOD:
+		args->value = ctx->hang_stats.ban_period_seconds;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+	mutex_unlock(&dev->struct_mutex);
+
+	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 intel_context *ctx;
+	int ret;
+
+	ret = i915_mutex_lock_interruptible(dev);
+	if (ret)
+		return ret;
+
+	ctx = i915_gem_context_get(file_priv, args->ctx_id);
+	if (IS_ERR(ctx)) {
+		mutex_unlock(&dev->struct_mutex);
+		return PTR_ERR(ctx);
+	}
+
+	switch (args->param) {
+	case I915_CONTEXT_PARAM_BAN_PERIOD:
+		if (args->size)
+			ret = -EINVAL;
+		else if (args->value < ctx->hang_stats.ban_period_seconds &&
+			 !capable(CAP_SYS_ADMIN))
+			ret = -EPERM;
+		else
+			ctx->hang_stats.ban_period_seconds = args->value;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+	mutex_unlock(&dev->struct_mutex);
+
+	return ret;
+}