i915/gt/intel_context.c

/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright © 2019 Intel Corporation
 */

#include "gem/i915_gem_context.h"
#include "gem/i915_gem_pm.h"

#include "i915_drv.h"
#include "i915_globals.h"

#include "intel_context.h"
#include "intel_engine.h"
#include "intel_engine_pm.h"
#include "intel_ring.h"

static struct i915_global_context {
	struct i915_global base;
	struct kmem_cache *slab_ce;
} global;

static 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_create(struct i915_gem_context *ctx,
		     struct intel_engine_cs *engine)
{
	struct intel_context *ce;

	ce = intel_context_alloc();
	if (!ce)
		return ERR_PTR(-ENOMEM);

	intel_context_init(ce, ctx, engine);
	return ce;
}

int __intel_context_do_pin(struct intel_context *ce)
{
	int err;

	if (mutex_lock_interruptible(&ce->pin_mutex))
		return -EINTR;

	if (likely(!atomic_read(&ce->pin_count))) {
		intel_wakeref_t wakeref;

		if (unlikely(!test_bit(CONTEXT_ALLOC_BIT, &ce->flags))) {
			err = ce->ops->alloc(ce);
			if (unlikely(err))
				goto err;

			__set_bit(CONTEXT_ALLOC_BIT, &ce->flags);
		}

		err = 0;
		with_intel_runtime_pm(ce->engine->uncore->rpm, wakeref)
			err = ce->ops->pin(ce);
		if (err)
			goto err;

		GEM_TRACE("%s context:%llx pin ring:{head:%04x, tail:%04x}\n",
			  ce->engine->name, ce->timeline->fence_context,
			  ce->ring->head, ce->ring->tail);

		i915_gem_context_get(ce->gem_context); /* for ctx->ppgtt */

		smp_mb__before_atomic(); /* flush pin before it is visible */
	}

	atomic_inc(&ce->pin_count);
	GEM_BUG_ON(!intel_context_is_pinned(ce)); /* no overflow! */

	mutex_unlock(&ce->pin_mutex);
	return 0;

err:
	mutex_unlock(&ce->pin_mutex);
	return err;
}

void intel_context_unpin(struct intel_context *ce)
{
	if (likely(atomic_add_unless(&ce->pin_count, -1, 1)))
		return;

	/* We may be called from inside intel_context_pin() to evict another */
	intel_context_get(ce);
	mutex_lock_nested(&ce->pin_mutex, SINGLE_DEPTH_NESTING);

	if (likely(atomic_dec_and_test(&ce->pin_count))) {
		GEM_TRACE("%s context:%llx retire\n",
			  ce->engine->name, ce->timeline->fence_context);

		ce->ops->unpin(ce);

		i915_gem_context_put(ce->gem_context);
		intel_context_active_release(ce);
	}

	mutex_unlock(&ce->pin_mutex);
	intel_context_put(ce);
}

static int __context_pin_state(struct i915_vma *vma)
{
	u64 flags;
	int err;

	flags = i915_ggtt_pin_bias(vma) | PIN_OFFSET_BIAS;
	flags |= PIN_HIGH | PIN_GLOBAL;

	err = i915_vma_pin(vma, 0, 0, flags);
	if (err)
		return err;

	err = i915_active_acquire(&vma->active);
	if (err)
		goto err_unpin;

	/*
	 * And mark it as a globally pinned object to let the shrinker know
	 * it cannot reclaim the object until we release it.
	 */
	i915_vma_make_unshrinkable(vma);
	vma->obj->mm.dirty = true;

	return 0;

err_unpin:
	i915_vma_unpin(vma);
	return err;
}

static void __context_unpin_state(struct i915_vma *vma)
{
	i915_vma_make_shrinkable(vma);
	i915_active_release(&vma->active);
	__i915_vma_unpin(vma);
}

static int __ring_active(struct intel_ring *ring)
{
	int err;

	err = i915_active_acquire(&ring->vma->active);
	if (err)
		return err;

	err = intel_ring_pin(ring);
	if (err)
		goto err_active;

	return 0;

err_active:
	i915_active_release(&ring->vma->active);
	return err;
}

static void __ring_retire(struct intel_ring *ring)
{
	intel_ring_unpin(ring);
	i915_active_release(&ring->vma->active);
}

__i915_active_call
static void __intel_context_retire(struct i915_active *active)
{
	struct intel_context *ce = container_of(active, typeof(*ce), active);

	GEM_TRACE("%s context:%llx retire\n",
		  ce->engine->name, ce->timeline->fence_context);

	if (ce->state)
		__context_unpin_state(ce->state);

	intel_timeline_unpin(ce->timeline);
	__ring_retire(ce->ring);

	intel_context_put(ce);
}

static int __intel_context_active(struct i915_active *active)
{
	struct intel_context *ce = container_of(active, typeof(*ce), active);
	int err;

	intel_context_get(ce);

	err = __ring_active(ce->ring);
	if (err)
		goto err_put;

	err = intel_timeline_pin(ce->timeline);
	if (err)
		goto err_ring;

	if (!ce->state)
		return 0;

	err = __context_pin_state(ce->state);
	if (err)
		goto err_timeline;

	return 0;

err_timeline:
	intel_timeline_unpin(ce->timeline);
err_ring:
	__ring_retire(ce->ring);
err_put:
	intel_context_put(ce);
	return err;
}

int intel_context_active_acquire(struct intel_context *ce)
{
	int err;

	err = i915_active_acquire(&ce->active);
	if (err)
		return err;

	/* Preallocate tracking nodes */
	if (!i915_gem_context_is_kernel(ce->gem_context)) {
		err = i915_active_acquire_preallocate_barrier(&ce->active,
							      ce->engine);
		if (err) {
			i915_active_release(&ce->active);
			return err;
		}
	}

	return 0;
}

void intel_context_active_release(struct intel_context *ce)
{
	/* Nodes preallocated in intel_context_active() */
	i915_active_acquire_barrier(&ce->active);
	i915_active_release(&ce->active);
}

void
intel_context_init(struct intel_context *ce,
		   struct i915_gem_context *ctx,
		   struct intel_engine_cs *engine)
{
	struct i915_address_space *vm;

	GEM_BUG_ON(!engine->cops);

	kref_init(&ce->ref);

	ce->gem_context = ctx;
	rcu_read_lock();
	vm = rcu_dereference(ctx->vm);
	if (vm)
		ce->vm = i915_vm_get(vm);
	else
		ce->vm = i915_vm_get(&engine->gt->ggtt->vm);
	rcu_read_unlock();
	if (ctx->timeline)
		ce->timeline = intel_timeline_get(ctx->timeline);

	ce->engine = engine;
	ce->ops = engine->cops;
	ce->sseu = engine->sseu;
	ce->ring = __intel_context_ring_size(SZ_16K);

	INIT_LIST_HEAD(&ce->signal_link);
	INIT_LIST_HEAD(&ce->signals);

	mutex_init(&ce->pin_mutex);

	i915_active_init(&ce->active,
			 __intel_context_active, __intel_context_retire);
}

void intel_context_fini(struct intel_context *ce)
{
	if (ce->timeline)
		intel_timeline_put(ce->timeline);
	i915_vm_put(ce->vm);

	mutex_destroy(&ce->pin_mutex);
	i915_active_fini(&ce->active);
}

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;
}

void intel_context_enter_engine(struct intel_context *ce)
{
	intel_engine_pm_get(ce->engine);
	intel_timeline_enter(ce->timeline);
}

void intel_context_exit_engine(struct intel_context *ce)
{
	intel_timeline_exit(ce->timeline);
	intel_engine_pm_put(ce->engine);
}

int intel_context_prepare_remote_request(struct intel_context *ce,
					 struct i915_request *rq)
{
	struct intel_timeline *tl = ce->timeline;
	int err;

	/* Only suitable for use in remotely modifying this context */
	GEM_BUG_ON(rq->hw_context == ce);

	if (rcu_access_pointer(rq->timeline) != tl) { /* timeline sharing! */
		/*
		 * Ideally, we just want to insert our foreign fence as
		 * a barrier into the remove context, such that this operation
		 * occurs after all current operations in that context, and
		 * all future operations must occur after this.
		 *
		 * Currently, the timeline->last_request tracking is guarded
		 * by its mutex and so we must obtain that to atomically
		 * insert our barrier. However, since we already hold our
		 * timeline->mutex, we must be careful against potential
		 * inversion if we are the kernel_context as the remote context
		 * will itself poke at the kernel_context when it needs to
		 * unpin. Ergo, if already locked, we drop both locks and
		 * try again (through the magic of userspace repeating EAGAIN).
		 */
		if (!mutex_trylock(&tl->mutex))
			return -EAGAIN;

		/* Queue this switch after current activity by this context. */
		err = i915_active_fence_set(&tl->last_request, rq);
		mutex_unlock(&tl->mutex);
		if (err)
			return err;
	}

	/*
	 * Guarantee context image and the timeline remains pinned until the
	 * modifying request is retired by setting the ce activity tracker.
	 *
	 * But we only need to take one pin on the account of it. Or in other
	 * words transfer the pinned ce object to tracked active request.
	 */
	GEM_BUG_ON(i915_active_is_idle(&ce->active));
	return i915_active_add_request(&ce->active, rq);
}

struct i915_request *intel_context_create_request(struct intel_context *ce)
{
	struct i915_request *rq;
	int err;

	err = intel_context_pin(ce);
	if (unlikely(err))
		return ERR_PTR(err);

	rq = i915_request_create(ce);
	intel_context_unpin(ce);

	return rq;
}

#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
#include "selftest_context.c"
#endif