Contributors: 2
Author Tokens Token Proportion Commits Commit Proportion
Chris Wilson 4722 98.66% 23 88.46%
Tvrtko A. Ursulin 64 1.34% 3 11.54%
Total 4786 26 


/*
 * SPDX-License-Identifier: MIT
 *
 * Copyright © 2017-2018 Intel Corporation
 */

#include <linux/prime_numbers.h>

#include "intel_context.h"
#include "intel_engine_heartbeat.h"
#include "intel_engine_pm.h"
#include "intel_gt.h"
#include "intel_gt_requests.h"
#include "intel_ring.h"
#include "selftest_engine_heartbeat.h"

#include "../selftests/i915_random.h"
#include "../i915_selftest.h"

#include "../selftests/igt_flush_test.h"
#include "../selftests/mock_gem_device.h"
#include "selftests/mock_timeline.h"

static struct page *hwsp_page(struct intel_timeline *tl)
{
	struct drm_i915_gem_object *obj = tl->hwsp_ggtt->obj;

	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
	return sg_page(obj->mm.pages->sgl);
}

static unsigned long hwsp_cacheline(struct intel_timeline *tl)
{
	unsigned long address = (unsigned long)page_address(hwsp_page(tl));

	return (address + tl->hwsp_offset) / CACHELINE_BYTES;
}

#define CACHELINES_PER_PAGE (PAGE_SIZE / CACHELINE_BYTES)

struct mock_hwsp_freelist {
	struct intel_gt *gt;
	struct radix_tree_root cachelines;
	struct intel_timeline **history;
	unsigned long count, max;
	struct rnd_state prng;
};

enum {
	SHUFFLE = BIT(0),
};

static void __mock_hwsp_record(struct mock_hwsp_freelist *state,
			       unsigned int idx,
			       struct intel_timeline *tl)
{
	tl = xchg(&state->history[idx], tl);
	if (tl) {
		radix_tree_delete(&state->cachelines, hwsp_cacheline(tl));
		intel_timeline_put(tl);
	}
}

static int __mock_hwsp_timeline(struct mock_hwsp_freelist *state,
				unsigned int count,
				unsigned int flags)
{
	struct intel_timeline *tl;
	unsigned int idx;

	while (count--) {
		unsigned long cacheline;
		int err;

		tl = intel_timeline_create(state->gt, NULL);
		if (IS_ERR(tl))
			return PTR_ERR(tl);

		cacheline = hwsp_cacheline(tl);
		err = radix_tree_insert(&state->cachelines, cacheline, tl);
		if (err) {
			if (err == -EEXIST) {
				pr_err("HWSP cacheline %lu already used; duplicate allocation!\n",
				       cacheline);
			}
			intel_timeline_put(tl);
			return err;
		}

		idx = state->count++ % state->max;
		__mock_hwsp_record(state, idx, tl);
	}

	if (flags & SHUFFLE)
		i915_prandom_shuffle(state->history,
				     sizeof(*state->history),
				     min(state->count, state->max),
				     &state->prng);

	count = i915_prandom_u32_max_state(min(state->count, state->max),
					   &state->prng);
	while (count--) {
		idx = --state->count % state->max;
		__mock_hwsp_record(state, idx, NULL);
	}

	return 0;
}

static int mock_hwsp_freelist(void *arg)
{
	struct mock_hwsp_freelist state;
	struct drm_i915_private *i915;
	const struct {
		const char *name;
		unsigned int flags;
	} phases[] = {
		{ "linear", 0 },
		{ "shuffled", SHUFFLE },
		{ },
	}, *p;
	unsigned int na;
	int err = 0;

	i915 = mock_gem_device();
	if (!i915)
		return -ENOMEM;

	INIT_RADIX_TREE(&state.cachelines, GFP_KERNEL);
	state.prng = I915_RND_STATE_INITIALIZER(i915_selftest.random_seed);

	state.gt = &i915->gt;

	/*
	 * Create a bunch of timelines and check that their HWSP do not overlap.
	 * Free some, and try again.
	 */

	state.max = PAGE_SIZE / sizeof(*state.history);
	state.count = 0;
	state.history = kcalloc(state.max, sizeof(*state.history), GFP_KERNEL);
	if (!state.history) {
		err = -ENOMEM;
		goto err_put;
	}

	for (p = phases; p->name; p++) {
		pr_debug("%s(%s)\n", __func__, p->name);
		for_each_prime_number_from(na, 1, 2 * CACHELINES_PER_PAGE) {
			err = __mock_hwsp_timeline(&state, na, p->flags);
			if (err)
				goto out;
		}
	}

out:
	for (na = 0; na < state.max; na++)
		__mock_hwsp_record(&state, na, NULL);
	kfree(state.history);
err_put:
	drm_dev_put(&i915->drm);
	return err;
}

struct __igt_sync {
	const char *name;
	u32 seqno;
	bool expected;
	bool set;
};

static int __igt_sync(struct intel_timeline *tl,
		      u64 ctx,
		      const struct __igt_sync *p,
		      const char *name)
{
	int ret;

	if (__intel_timeline_sync_is_later(tl, ctx, p->seqno) != p->expected) {
		pr_err("%s: %s(ctx=%llu, seqno=%u) expected passed %s but failed\n",
		       name, p->name, ctx, p->seqno, yesno(p->expected));
		return -EINVAL;
	}

	if (p->set) {
		ret = __intel_timeline_sync_set(tl, ctx, p->seqno);
		if (ret)
			return ret;
	}

	return 0;
}

static int igt_sync(void *arg)
{
	const struct __igt_sync pass[] = {
		{ "unset", 0, false, false },
		{ "new", 0, false, true },
		{ "0a", 0, true, true },
		{ "1a", 1, false, true },
		{ "1b", 1, true, true },
		{ "0b", 0, true, false },
		{ "2a", 2, false, true },
		{ "4", 4, false, true },
		{ "INT_MAX", INT_MAX, false, true },
		{ "INT_MAX-1", INT_MAX-1, true, false },
		{ "INT_MAX+1", (u32)INT_MAX+1, false, true },
		{ "INT_MAX", INT_MAX, true, false },
		{ "UINT_MAX", UINT_MAX, false, true },
		{ "wrap", 0, false, true },
		{ "unwrap", UINT_MAX, true, false },
		{},
	}, *p;
	struct intel_timeline tl;
	int order, offset;
	int ret = -ENODEV;

	mock_timeline_init(&tl, 0);
	for (p = pass; p->name; p++) {
		for (order = 1; order < 64; order++) {
			for (offset = -1; offset <= (order > 1); offset++) {
				u64 ctx = BIT_ULL(order) + offset;

				ret = __igt_sync(&tl, ctx, p, "1");
				if (ret)
					goto out;
			}
		}
	}
	mock_timeline_fini(&tl);

	mock_timeline_init(&tl, 0);
	for (order = 1; order < 64; order++) {
		for (offset = -1; offset <= (order > 1); offset++) {
			u64 ctx = BIT_ULL(order) + offset;

			for (p = pass; p->name; p++) {
				ret = __igt_sync(&tl, ctx, p, "2");
				if (ret)
					goto out;
			}
		}
	}

out:
	mock_timeline_fini(&tl);
	return ret;
}

static unsigned int random_engine(struct rnd_state *rnd)
{
	return i915_prandom_u32_max_state(I915_NUM_ENGINES, rnd);
}

static int bench_sync(void *arg)
{
	struct rnd_state prng;
	struct intel_timeline tl;
	unsigned long end_time, count;
	u64 prng32_1M;
	ktime_t kt;
	int order, last_order;

	mock_timeline_init(&tl, 0);

	/* Lookups from cache are very fast and so the random number generation
	 * and the loop itself becomes a significant factor in the per-iteration
	 * timings. We try to compensate the results by measuring the overhead
	 * of the prng and subtract it from the reported results.
	 */
	prandom_seed_state(&prng, i915_selftest.random_seed);
	count = 0;
	kt = ktime_get();
	end_time = jiffies + HZ/10;
	do {
		u32 x;

		/* Make sure the compiler doesn't optimise away the prng call */
		WRITE_ONCE(x, prandom_u32_state(&prng));

		count++;
	} while (!time_after(jiffies, end_time));
	kt = ktime_sub(ktime_get(), kt);
	pr_debug("%s: %lu random evaluations, %lluns/prng\n",
		 __func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
	prng32_1M = div64_ul(ktime_to_ns(kt) << 20, count);

	/* Benchmark (only) setting random context ids */
	prandom_seed_state(&prng, i915_selftest.random_seed);
	count = 0;
	kt = ktime_get();
	end_time = jiffies + HZ/10;
	do {
		u64 id = i915_prandom_u64_state(&prng);

		__intel_timeline_sync_set(&tl, id, 0);
		count++;
	} while (!time_after(jiffies, end_time));
	kt = ktime_sub(ktime_get(), kt);
	kt = ktime_sub_ns(kt, (count * prng32_1M * 2) >> 20);
	pr_info("%s: %lu random insertions, %lluns/insert\n",
		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));

	/* Benchmark looking up the exact same context ids as we just set */
	prandom_seed_state(&prng, i915_selftest.random_seed);
	end_time = count;
	kt = ktime_get();
	while (end_time--) {
		u64 id = i915_prandom_u64_state(&prng);

		if (!__intel_timeline_sync_is_later(&tl, id, 0)) {
			mock_timeline_fini(&tl);
			pr_err("Lookup of %llu failed\n", id);
			return -EINVAL;
		}
	}
	kt = ktime_sub(ktime_get(), kt);
	kt = ktime_sub_ns(kt, (count * prng32_1M * 2) >> 20);
	pr_info("%s: %lu random lookups, %lluns/lookup\n",
		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));

	mock_timeline_fini(&tl);
	cond_resched();

	mock_timeline_init(&tl, 0);

	/* Benchmark setting the first N (in order) contexts */
	count = 0;
	kt = ktime_get();
	end_time = jiffies + HZ/10;
	do {
		__intel_timeline_sync_set(&tl, count++, 0);
	} while (!time_after(jiffies, end_time));
	kt = ktime_sub(ktime_get(), kt);
	pr_info("%s: %lu in-order insertions, %lluns/insert\n",
		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));

	/* Benchmark looking up the exact same context ids as we just set */
	end_time = count;
	kt = ktime_get();
	while (end_time--) {
		if (!__intel_timeline_sync_is_later(&tl, end_time, 0)) {
			pr_err("Lookup of %lu failed\n", end_time);
			mock_timeline_fini(&tl);
			return -EINVAL;
		}
	}
	kt = ktime_sub(ktime_get(), kt);
	pr_info("%s: %lu in-order lookups, %lluns/lookup\n",
		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));

	mock_timeline_fini(&tl);
	cond_resched();

	mock_timeline_init(&tl, 0);

	/* Benchmark searching for a random context id and maybe changing it */
	prandom_seed_state(&prng, i915_selftest.random_seed);
	count = 0;
	kt = ktime_get();
	end_time = jiffies + HZ/10;
	do {
		u32 id = random_engine(&prng);
		u32 seqno = prandom_u32_state(&prng);

		if (!__intel_timeline_sync_is_later(&tl, id, seqno))
			__intel_timeline_sync_set(&tl, id, seqno);

		count++;
	} while (!time_after(jiffies, end_time));
	kt = ktime_sub(ktime_get(), kt);
	kt = ktime_sub_ns(kt, (count * prng32_1M * 2) >> 20);
	pr_info("%s: %lu repeated insert/lookups, %lluns/op\n",
		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
	mock_timeline_fini(&tl);
	cond_resched();

	/* Benchmark searching for a known context id and changing the seqno */
	for (last_order = 1, order = 1; order < 32;
	     ({ int tmp = last_order; last_order = order; order += tmp; })) {
		unsigned int mask = BIT(order) - 1;

		mock_timeline_init(&tl, 0);

		count = 0;
		kt = ktime_get();
		end_time = jiffies + HZ/10;
		do {
			/* Without assuming too many details of the underlying
			 * implementation, try to identify its phase-changes
			 * (if any)!
			 */
			u64 id = (u64)(count & mask) << order;

			__intel_timeline_sync_is_later(&tl, id, 0);
			__intel_timeline_sync_set(&tl, id, 0);

			count++;
		} while (!time_after(jiffies, end_time));
		kt = ktime_sub(ktime_get(), kt);
		pr_info("%s: %lu cyclic/%d insert/lookups, %lluns/op\n",
			__func__, count, order,
			(long long)div64_ul(ktime_to_ns(kt), count));
		mock_timeline_fini(&tl);
		cond_resched();
	}

	return 0;
}

int intel_timeline_mock_selftests(void)
{
	static const struct i915_subtest tests[] = {
		SUBTEST(mock_hwsp_freelist),
		SUBTEST(igt_sync),
		SUBTEST(bench_sync),
	};

	return i915_subtests(tests, NULL);
}

static int emit_ggtt_store_dw(struct i915_request *rq, u32 addr, u32 value)
{
	u32 *cs;

	cs = intel_ring_begin(rq, 4);
	if (IS_ERR(cs))
		return PTR_ERR(cs);

	if (INTEL_GEN(rq->engine->i915) >= 8) {
		*cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
		*cs++ = addr;
		*cs++ = 0;
		*cs++ = value;
	} else if (INTEL_GEN(rq->engine->i915) >= 4) {
		*cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
		*cs++ = 0;
		*cs++ = addr;
		*cs++ = value;
	} else {
		*cs++ = MI_STORE_DWORD_IMM | MI_MEM_VIRTUAL;
		*cs++ = addr;
		*cs++ = value;
		*cs++ = MI_NOOP;
	}

	intel_ring_advance(rq, cs);

	return 0;
}

static struct i915_request *
tl_write(struct intel_timeline *tl, struct intel_engine_cs *engine, u32 value)
{
	struct i915_request *rq;
	int err;

	err = intel_timeline_pin(tl);
	if (err) {
		rq = ERR_PTR(err);
		goto out;
	}

	rq = intel_engine_create_kernel_request(engine);
	if (IS_ERR(rq))
		goto out_unpin;

	i915_request_get(rq);

	err = emit_ggtt_store_dw(rq, tl->hwsp_offset, value);
	i915_request_add(rq);
	if (err) {
		i915_request_put(rq);
		rq = ERR_PTR(err);
	}

out_unpin:
	intel_timeline_unpin(tl);
out:
	if (IS_ERR(rq))
		pr_err("Failed to write to timeline!\n");
	return rq;
}

static struct intel_timeline *
checked_intel_timeline_create(struct intel_gt *gt)
{
	struct intel_timeline *tl;

	tl = intel_timeline_create(gt, NULL);
	if (IS_ERR(tl))
		return tl;

	if (*tl->hwsp_seqno != tl->seqno) {
		pr_err("Timeline created with incorrect breadcrumb, found %x, expected %x\n",
		       *tl->hwsp_seqno, tl->seqno);
		intel_timeline_put(tl);
		return ERR_PTR(-EINVAL);
	}

	return tl;
}

static int live_hwsp_engine(void *arg)
{
#define NUM_TIMELINES 4096
	struct intel_gt *gt = arg;
	struct intel_timeline **timelines;
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	unsigned long count, n;
	int err = 0;

	/*
	 * Create a bunch of timelines and check we can write
	 * independently to each of their breadcrumb slots.
	 */

	timelines = kvmalloc_array(NUM_TIMELINES * I915_NUM_ENGINES,
				   sizeof(*timelines),
				   GFP_KERNEL);
	if (!timelines)
		return -ENOMEM;

	count = 0;
	for_each_engine(engine, gt, id) {
		if (!intel_engine_can_store_dword(engine))
			continue;

		intel_engine_pm_get(engine);

		for (n = 0; n < NUM_TIMELINES; n++) {
			struct intel_timeline *tl;
			struct i915_request *rq;

			tl = checked_intel_timeline_create(gt);
			if (IS_ERR(tl)) {
				err = PTR_ERR(tl);
				break;
			}

			rq = tl_write(tl, engine, count);
			if (IS_ERR(rq)) {
				intel_timeline_put(tl);
				err = PTR_ERR(rq);
				break;
			}

			timelines[count++] = tl;
			i915_request_put(rq);
		}

		intel_engine_pm_put(engine);
		if (err)
			break;
	}

	if (igt_flush_test(gt->i915))
		err = -EIO;

	for (n = 0; n < count; n++) {
		struct intel_timeline *tl = timelines[n];

		if (!err && *tl->hwsp_seqno != n) {
			pr_err("Invalid seqno stored in timeline %lu @ %x, found 0x%x\n",
			       n, tl->hwsp_offset, *tl->hwsp_seqno);
			GEM_TRACE_DUMP();
			err = -EINVAL;
		}
		intel_timeline_put(tl);
	}

	kvfree(timelines);
	return err;
#undef NUM_TIMELINES
}

static int live_hwsp_alternate(void *arg)
{
#define NUM_TIMELINES 4096
	struct intel_gt *gt = arg;
	struct intel_timeline **timelines;
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	unsigned long count, n;
	int err = 0;

	/*
	 * Create a bunch of timelines and check we can write
	 * independently to each of their breadcrumb slots with adjacent
	 * engines.
	 */

	timelines = kvmalloc_array(NUM_TIMELINES * I915_NUM_ENGINES,
				   sizeof(*timelines),
				   GFP_KERNEL);
	if (!timelines)
		return -ENOMEM;

	count = 0;
	for (n = 0; n < NUM_TIMELINES; n++) {
		for_each_engine(engine, gt, id) {
			struct intel_timeline *tl;
			struct i915_request *rq;

			if (!intel_engine_can_store_dword(engine))
				continue;

			tl = checked_intel_timeline_create(gt);
			if (IS_ERR(tl)) {
				err = PTR_ERR(tl);
				goto out;
			}

			intel_engine_pm_get(engine);
			rq = tl_write(tl, engine, count);
			intel_engine_pm_put(engine);
			if (IS_ERR(rq)) {
				intel_timeline_put(tl);
				err = PTR_ERR(rq);
				goto out;
			}

			timelines[count++] = tl;
			i915_request_put(rq);
		}
	}

out:
	if (igt_flush_test(gt->i915))
		err = -EIO;

	for (n = 0; n < count; n++) {
		struct intel_timeline *tl = timelines[n];

		if (!err && *tl->hwsp_seqno != n) {
			pr_err("Invalid seqno stored in timeline %lu @ %x, found 0x%x\n",
			       n, tl->hwsp_offset, *tl->hwsp_seqno);
			GEM_TRACE_DUMP();
			err = -EINVAL;
		}
		intel_timeline_put(tl);
	}

	kvfree(timelines);
	return err;
#undef NUM_TIMELINES
}

static int live_hwsp_wrap(void *arg)
{
	struct intel_gt *gt = arg;
	struct intel_engine_cs *engine;
	struct intel_timeline *tl;
	enum intel_engine_id id;
	int err = 0;

	/*
	 * Across a seqno wrap, we need to keep the old cacheline alive for
	 * foreign GPU references.
	 */

	tl = intel_timeline_create(gt, NULL);
	if (IS_ERR(tl))
		return PTR_ERR(tl);

	if (!tl->has_initial_breadcrumb || !tl->hwsp_cacheline)
		goto out_free;

	err = intel_timeline_pin(tl);
	if (err)
		goto out_free;

	for_each_engine(engine, gt, id) {
		const u32 *hwsp_seqno[2];
		struct i915_request *rq;
		u32 seqno[2];

		if (!intel_engine_can_store_dword(engine))
			continue;

		rq = intel_engine_create_kernel_request(engine);
		if (IS_ERR(rq)) {
			err = PTR_ERR(rq);
			goto out;
		}

		tl->seqno = -4u;

		mutex_lock_nested(&tl->mutex, SINGLE_DEPTH_NESTING);
		err = intel_timeline_get_seqno(tl, rq, &seqno[0]);
		mutex_unlock(&tl->mutex);
		if (err) {
			i915_request_add(rq);
			goto out;
		}
		pr_debug("seqno[0]:%08x, hwsp_offset:%08x\n",
			 seqno[0], tl->hwsp_offset);

		err = emit_ggtt_store_dw(rq, tl->hwsp_offset, seqno[0]);
		if (err) {
			i915_request_add(rq);
			goto out;
		}
		hwsp_seqno[0] = tl->hwsp_seqno;

		mutex_lock_nested(&tl->mutex, SINGLE_DEPTH_NESTING);
		err = intel_timeline_get_seqno(tl, rq, &seqno[1]);
		mutex_unlock(&tl->mutex);
		if (err) {
			i915_request_add(rq);
			goto out;
		}
		pr_debug("seqno[1]:%08x, hwsp_offset:%08x\n",
			 seqno[1], tl->hwsp_offset);

		err = emit_ggtt_store_dw(rq, tl->hwsp_offset, seqno[1]);
		if (err) {
			i915_request_add(rq);
			goto out;
		}
		hwsp_seqno[1] = tl->hwsp_seqno;

		/* With wrap should come a new hwsp */
		GEM_BUG_ON(seqno[1] >= seqno[0]);
		GEM_BUG_ON(hwsp_seqno[0] == hwsp_seqno[1]);

		i915_request_add(rq);

		if (i915_request_wait(rq, 0, HZ / 5) < 0) {
			pr_err("Wait for timeline writes timed out!\n");
			err = -EIO;
			goto out;
		}

		if (*hwsp_seqno[0] != seqno[0] || *hwsp_seqno[1] != seqno[1]) {
			pr_err("Bad timeline values: found (%x, %x), expected (%x, %x)\n",
			       *hwsp_seqno[0], *hwsp_seqno[1],
			       seqno[0], seqno[1]);
			err = -EINVAL;
			goto out;
		}

		intel_gt_retire_requests(gt); /* recycle HWSP */
	}

out:
	if (igt_flush_test(gt->i915))
		err = -EIO;

	intel_timeline_unpin(tl);
out_free:
	intel_timeline_put(tl);
	return err;
}

static int live_hwsp_rollover_kernel(void *arg)
{
	struct intel_gt *gt = arg;
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	int err = 0;

	/*
	 * Run the host for long enough, and even the kernel context will
	 * see a seqno rollover.
	 */

	for_each_engine(engine, gt, id) {
		struct intel_context *ce = engine->kernel_context;
		struct intel_timeline *tl = ce->timeline;
		struct i915_request *rq[3] = {};
		int i;

		st_engine_heartbeat_disable(engine);
		if (intel_gt_wait_for_idle(gt, HZ / 2)) {
			err = -EIO;
			goto out;
		}

		GEM_BUG_ON(i915_active_fence_isset(&tl->last_request));
		tl->seqno = 0;
		timeline_rollback(tl);
		timeline_rollback(tl);
		WRITE_ONCE(*(u32 *)tl->hwsp_seqno, tl->seqno);

		for (i = 0; i < ARRAY_SIZE(rq); i++) {
			struct i915_request *this;

			this = i915_request_create(ce);
			if (IS_ERR(this)) {
				err = PTR_ERR(this);
				goto out;
			}

			pr_debug("%s: create fence.seqnp:%d\n",
				 engine->name,
				 lower_32_bits(this->fence.seqno));

			GEM_BUG_ON(rcu_access_pointer(this->timeline) != tl);

			rq[i] = i915_request_get(this);
			i915_request_add(this);
		}

		/* We expected a wrap! */
		GEM_BUG_ON(rq[2]->fence.seqno > rq[0]->fence.seqno);

		if (i915_request_wait(rq[2], 0, HZ / 5) < 0) {
			pr_err("Wait for timeline wrap timed out!\n");
			err = -EIO;
			goto out;
		}

		for (i = 0; i < ARRAY_SIZE(rq); i++) {
			if (!i915_request_completed(rq[i])) {
				pr_err("Pre-wrap request not completed!\n");
				err = -EINVAL;
				goto out;
			}
		}

out:
		for (i = 0; i < ARRAY_SIZE(rq); i++)
			i915_request_put(rq[i]);
		st_engine_heartbeat_enable(engine);
		if (err)
			break;
	}

	if (igt_flush_test(gt->i915))
		err = -EIO;

	return err;
}

static int live_hwsp_rollover_user(void *arg)
{
	struct intel_gt *gt = arg;
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	int err = 0;

	/*
	 * Simulate a long running user context, and force the seqno wrap
	 * on the user's timeline.
	 */

	for_each_engine(engine, gt, id) {
		struct i915_request *rq[3] = {};
		struct intel_timeline *tl;
		struct intel_context *ce;
		int i;

		ce = intel_context_create(engine);
		if (IS_ERR(ce))
			return PTR_ERR(ce);

		err = intel_context_alloc_state(ce);
		if (err)
			goto out;

		tl = ce->timeline;
		if (!tl->has_initial_breadcrumb || !tl->hwsp_cacheline)
			goto out;

		timeline_rollback(tl);
		timeline_rollback(tl);
		WRITE_ONCE(*(u32 *)tl->hwsp_seqno, tl->seqno);

		for (i = 0; i < ARRAY_SIZE(rq); i++) {
			struct i915_request *this;

			this = intel_context_create_request(ce);
			if (IS_ERR(this)) {
				err = PTR_ERR(this);
				goto out;
			}

			pr_debug("%s: create fence.seqnp:%d\n",
				 engine->name,
				 lower_32_bits(this->fence.seqno));

			GEM_BUG_ON(rcu_access_pointer(this->timeline) != tl);

			rq[i] = i915_request_get(this);
			i915_request_add(this);
		}

		/* We expected a wrap! */
		GEM_BUG_ON(rq[2]->fence.seqno > rq[0]->fence.seqno);

		if (i915_request_wait(rq[2], 0, HZ / 5) < 0) {
			pr_err("Wait for timeline wrap timed out!\n");
			err = -EIO;
			goto out;
		}

		for (i = 0; i < ARRAY_SIZE(rq); i++) {
			if (!i915_request_completed(rq[i])) {
				pr_err("Pre-wrap request not completed!\n");
				err = -EINVAL;
				goto out;
			}
		}

out:
		for (i = 0; i < ARRAY_SIZE(rq); i++)
			i915_request_put(rq[i]);
		intel_context_put(ce);
		if (err)
			break;
	}

	if (igt_flush_test(gt->i915))
		err = -EIO;

	return err;
}

static int live_hwsp_recycle(void *arg)
{
	struct intel_gt *gt = arg;
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	unsigned long count;
	int err = 0;

	/*
	 * Check seqno writes into one timeline at a time. We expect to
	 * recycle the breadcrumb slot between iterations and neither
	 * want to confuse ourselves or the GPU.
	 */

	count = 0;
	for_each_engine(engine, gt, id) {
		IGT_TIMEOUT(end_time);

		if (!intel_engine_can_store_dword(engine))
			continue;

		intel_engine_pm_get(engine);

		do {
			struct intel_timeline *tl;
			struct i915_request *rq;

			tl = checked_intel_timeline_create(gt);
			if (IS_ERR(tl)) {
				err = PTR_ERR(tl);
				break;
			}

			rq = tl_write(tl, engine, count);
			if (IS_ERR(rq)) {
				intel_timeline_put(tl);
				err = PTR_ERR(rq);
				break;
			}

			if (i915_request_wait(rq, 0, HZ / 5) < 0) {
				pr_err("Wait for timeline writes timed out!\n");
				i915_request_put(rq);
				intel_timeline_put(tl);
				err = -EIO;
				break;
			}

			if (*tl->hwsp_seqno != count) {
				pr_err("Invalid seqno stored in timeline %lu @ tl->hwsp_offset, found 0x%x\n",
				       count, *tl->hwsp_seqno);
				GEM_TRACE_DUMP();
				err = -EINVAL;
			}

			i915_request_put(rq);
			intel_timeline_put(tl);
			count++;

			if (err)
				break;
		} while (!__igt_timeout(end_time, NULL));

		intel_engine_pm_put(engine);
		if (err)
			break;
	}

	return err;
}

int intel_timeline_live_selftests(struct drm_i915_private *i915)
{
	static const struct i915_subtest tests[] = {
		SUBTEST(live_hwsp_recycle),
		SUBTEST(live_hwsp_engine),
		SUBTEST(live_hwsp_alternate),
		SUBTEST(live_hwsp_wrap),
		SUBTEST(live_hwsp_rollover_kernel),
		SUBTEST(live_hwsp_rollover_user),
	};

	if (intel_gt_is_wedged(&i915->gt))
		return 0;

	return intel_gt_live_subtests(tests, &i915->gt);
}