drm/i915: Move over to intel_context_lookup()

In preparation for an ever growing number of engines and so ever
increasing static array of HW contexts within the GEM context, move the
array over to an rbtree, allocated upon first use.

Unfortunately, this imposes an rbtree lookup at a few frequent callsites,
but we should be able to mitigate those by moving over to using the HW
context as our primary type and so only incur the lookup on the boundary
with the user GEM context and engines.

v2: Check for no HW context in guc_stage_desc_init

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190308132522.21573-4-chris@chris-wilson.co.uk

1 files changed, 180 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_context.c b/drivers/gpu/drm/i915/intel_context.c
new file mode 100644
index 000000000000..d04a1f51a90c
--- /dev/null
+++ b/drivers/gpu/drm/i915/intel_context.c
@@ -0,0 +1,180 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2019 Intel Corporation
+ */
+
+#include "i915_drv.h"
+#include "i915_gem_context.h"
+#include "i915_globals.h"
+#include "intel_context.h"
+#include "intel_ringbuffer.h"
+
+static struct i915_global_context {
+	struct i915_global base;
+	struct kmem_cache *slab_ce;
+} global;
+
+struct intel_context *intel_context_alloc(void)
+{
+	return kmem_cache_zalloc(global.slab_ce, GFP_KERNEL);
+}
+
+void intel_context_free(struct intel_context *ce)
+{
+	kmem_cache_free(global.slab_ce, ce);
+}
+
+struct intel_context *
+intel_context_lookup(struct i915_gem_context *ctx,
+		     struct intel_engine_cs *engine)
+{
+	struct intel_context *ce = NULL;
+	struct rb_node *p;
+
+	spin_lock(&ctx->hw_contexts_lock);
+	p = ctx->hw_contexts.rb_node;
+	while (p) {
+		struct intel_context *this =
+			rb_entry(p, struct intel_context, node);
+
+		if (this->engine == engine) {
+			GEM_BUG_ON(this->gem_context != ctx);
+			ce = this;
+			break;
+		}
+
+		if (this->engine < engine)
+			p = p->rb_right;
+		else
+			p = p->rb_left;
+	}
+	spin_unlock(&ctx->hw_contexts_lock);
+
+	return ce;
+}
+
+struct intel_context *
+__intel_context_insert(struct i915_gem_context *ctx,
+		       struct intel_engine_cs *engine,
+		       struct intel_context *ce)
+{
+	struct rb_node **p, *parent;
+	int err = 0;
+
+	spin_lock(&ctx->hw_contexts_lock);
+
+	parent = NULL;
+	p = &ctx->hw_contexts.rb_node;
+	while (*p) {
+		struct intel_context *this;
+
+		parent = *p;
+		this = rb_entry(parent, struct intel_context, node);
+
+		if (this->engine == engine) {
+			err = -EEXIST;
+			ce = this;
+			break;
+		}
+
+		if (this->engine < engine)
+			p = &parent->rb_right;
+		else
+			p = &parent->rb_left;
+	}
+	if (!err) {
+		rb_link_node(&ce->node, parent, p);
+		rb_insert_color(&ce->node, &ctx->hw_contexts);
+	}
+
+	spin_unlock(&ctx->hw_contexts_lock);
+
+	return ce;
+}
+
+void __intel_context_remove(struct intel_context *ce)
+{
+	struct i915_gem_context *ctx = ce->gem_context;
+
+	spin_lock(&ctx->hw_contexts_lock);
+	rb_erase(&ce->node, &ctx->hw_contexts);
+	spin_unlock(&ctx->hw_contexts_lock);
+}
+
+struct intel_context *
+intel_context_instance(struct i915_gem_context *ctx,
+		       struct intel_engine_cs *engine)
+{
+	struct intel_context *ce, *pos;
+
+	ce = intel_context_lookup(ctx, engine);
+	if (likely(ce))
+		return ce;
+
+	ce = intel_context_alloc();
+	if (!ce)
+		return ERR_PTR(-ENOMEM);
+
+	intel_context_init(ce, ctx, engine);
+
+	pos = __intel_context_insert(ctx, engine, ce);
+	if (unlikely(pos != ce)) /* Beaten! Use their HW context instead */
+		intel_context_free(ce);
+
+	GEM_BUG_ON(intel_context_lookup(ctx, engine) != pos);
+	return pos;
+}
+
+static void intel_context_retire(struct i915_active_request *active,
+				 struct i915_request *rq)
+{
+	struct intel_context *ce =
+		container_of(active, typeof(*ce), active_tracker);
+
+	intel_context_unpin(ce);
+}
+
+void
+intel_context_init(struct intel_context *ce,
+		   struct i915_gem_context *ctx,
+		   struct intel_engine_cs *engine)
+{
+	ce->gem_context = ctx;
+	ce->engine = engine;
+	ce->ops = engine->cops;
+
+	INIT_LIST_HEAD(&ce->signal_link);
+	INIT_LIST_HEAD(&ce->signals);
+
+	/* Use the whole device by default */
+	ce->sseu = intel_device_default_sseu(ctx->i915);
+
+	i915_active_request_init(&ce->active_tracker,
+				 NULL, intel_context_retire);
+}
+
+static void i915_global_context_shrink(void)
+{
+	kmem_cache_shrink(global.slab_ce);
+}
+
+static void i915_global_context_exit(void)
+{
+	kmem_cache_destroy(global.slab_ce);
+}
+
+static struct i915_global_context global = { {
+	.shrink = i915_global_context_shrink,
+	.exit = i915_global_context_exit,
+} };
+
+int __init i915_global_context_init(void)
+{
+	global.slab_ce = KMEM_CACHE(intel_context, SLAB_HWCACHE_ALIGN);
+	if (!global.slab_ce)
+		return -ENOMEM;
+
+	i915_global_register(&global.base);
+	return 0;
+}