drivers/gpu/drm/i915/selftests/i915_gem_context.c

/*
 * Copyright © 2017 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.
 *
 */

#include <linux/prime_numbers.h>

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

#include "mock_drm.h"
#include "mock_gem_device.h"
#include "huge_gem_object.h"

#define DW_PER_PAGE (PAGE_SIZE / sizeof(u32))

struct live_test {
	struct drm_i915_private *i915;
	const char *func;
	const char *name;

	unsigned int reset_global;
	unsigned int reset_engine[I915_NUM_ENGINES];
};

static int begin_live_test(struct live_test *t,
			   struct drm_i915_private *i915,
			   const char *func,
			   const char *name)
{
	struct intel_engine_cs *engine;
	enum intel_engine_id id;
	int err;

	t->i915 = i915;
	t->func = func;
	t->name = name;

	err = i915_gem_wait_for_idle(i915,
				     I915_WAIT_LOCKED,
				     MAX_SCHEDULE_TIMEOUT);
	if (err) {
		pr_err("%s(%s): failed to idle before, with err=%d!",
		       func, name, err);
		return err;
	}

	i915->gpu_error.missed_irq_rings = 0;
	t->reset_global = i915_reset_count(&i915->gpu_error);

	for_each_engine(engine, i915, id)
		t->reset_engine[id] =
			i915_reset_engine_count(&i915->gpu_error, engine);

	return 0;
}

static int end_live_test(struct live_test *t)
{
	struct drm_i915_private *i915 = t->i915;
	struct intel_engine_cs *engine;
	enum intel_engine_id id;

	if (igt_flush_test(i915, I915_WAIT_LOCKED))
		return -EIO;

	if (t->reset_global != i915_reset_count(&i915->gpu_error)) {
		pr_err("%s(%s): GPU was reset %d times!\n",
		       t->func, t->name,
		       i915_reset_count(&i915->gpu_error) - t->reset_global);
		return -EIO;
	}

	for_each_engine(engine, i915, id) {
		if (t->reset_engine[id] ==
		    i915_reset_engine_count(&i915->gpu_error, engine))
			continue;

		pr_err("%s(%s): engine '%s' was reset %d times!\n",
		       t->func, t->name, engine->name,
		       i915_reset_engine_count(&i915->gpu_error, engine) -
		       t->reset_engine[id]);
		return -EIO;
	}

	if (i915->gpu_error.missed_irq_rings) {
		pr_err("%s(%s): Missed interrupts on engines %lx\n",
		       t->func, t->name, i915->gpu_error.missed_irq_rings);
		return -EIO;
	}

	return 0;
}

static int live_nop_switch(void *arg)
{
	const unsigned int nctx = 1024;
	struct drm_i915_private *i915 = arg;
	struct intel_engine_cs *engine;
	struct i915_gem_context **ctx;
	enum intel_engine_id id;
	struct drm_file *file;
	struct live_test t;
	unsigned long n;
	int err = -ENODEV;

	/*
	 * Create as many contexts as we can feasibly get away with
	 * and check we can switch between them rapidly.
	 *
	 * Serves as very simple stress test for submission and HW switching
	 * between contexts.
	 */

	if (!DRIVER_CAPS(i915)->has_logical_contexts)
		return 0;

	file = mock_file(i915);
	if (IS_ERR(file))
		return PTR_ERR(file);

	mutex_lock(&i915->drm.struct_mutex);
	intel_runtime_pm_get(i915);

	ctx = kcalloc(nctx, sizeof(*ctx), GFP_KERNEL);
	if (!ctx) {
		err = -ENOMEM;
		goto out_unlock;
	}

	for (n = 0; n < nctx; n++) {
		ctx[n] = i915_gem_create_context(i915, file->driver_priv);
		if (IS_ERR(ctx[n])) {
			err = PTR_ERR(ctx[n]);
			goto out_unlock;
		}
	}

	for_each_engine(engine, i915, id) {
		struct i915_request *rq;
		unsigned long end_time, prime;
		ktime_t times[2] = {};

		times[0] = ktime_get_raw();
		for (n = 0; n < nctx; n++) {
			rq = i915_request_alloc(engine, ctx[n]);
			if (IS_ERR(rq)) {
				err = PTR_ERR(rq);
				goto out_unlock;
			}
			i915_request_add(rq);
		}
		if (i915_request_wait(rq,
				      I915_WAIT_LOCKED,
				      HZ / 5) < 0) {
			pr_err("Failed to populated %d contexts\n", nctx);
			i915_gem_set_wedged(i915);
			err = -EIO;
			goto out_unlock;
		}

		times[1] = ktime_get_raw();

		pr_info("Populated %d contexts on %s in %lluns\n",
			nctx, engine->name, ktime_to_ns(times[1] - times[0]));

		err = begin_live_test(&t, i915, __func__, engine->name);
		if (err)
			goto out_unlock;

		end_time = jiffies + i915_selftest.timeout_jiffies;
		for_each_prime_number_from(prime, 2, 8192) {
			times[1] = ktime_get_raw();

			for (n = 0; n < prime; n++) {
				rq = i915_request_alloc(engine, ctx[n % nctx]);
				if (IS_ERR(rq)) {
					err = PTR_ERR(rq);
					goto out_unlock;
				}

				/*
				 * This space is left intentionally blank.
				 *
				 * We do not actually want to perform any
				 * action with this request, we just want
				 * to measure the latency in allocation
				 * and submission of our breadcrumbs -
				 * ensuring that the bare request is sufficient
				 * for the system to work (i.e. proper HEAD
				 * tracking of the rings, interrupt handling,
				 * etc). It also gives us the lowest bounds
				 * for latency.
				 */

				i915_request_add(rq);
			}
			if (i915_request_wait(rq,
					      I915_WAIT_LOCKED,
					      HZ / 5) < 0) {
				pr_err("Switching between %ld contexts timed out\n",
				       prime);
				i915_gem_set_wedged(i915);
				break;
			}

			times[1] = ktime_sub(ktime_get_raw(), times[1]);
			if (prime == 2)
				times[0] = times[1];

			if (__igt_timeout(end_time, NULL))
				break;
		}

		err = end_live_test(&t);
		if (err)
			goto out_unlock;

		pr_info("Switch latencies on %s: 1 = %lluns, %lu = %lluns\n",
			engine->name,
			ktime_to_ns(times[0]),
			prime - 1, div64_u64(ktime_to_ns(times[1]), prime - 1));
	}

out_unlock:
	intel_runtime_pm_put(i915);
	mutex_unlock(&i915->drm.struct_mutex);
	mock_file_free(i915, file);
	return err;
}

static struct i915_vma *
gpu_fill_dw(struct i915_vma *vma, u64 offset, unsigned long count, u32 value)
{
	struct drm_i915_gem_object *obj;
	const int gen = INTEL_GEN(vma->vm->i915);
	unsigned long n, size;
	u32 *cmd;
	int err;

	size = (4 * count + 1) * sizeof(u32);
	size = round_up(size, PAGE_SIZE);
	obj = i915_gem_object_create_internal(vma->vm->i915, size);
	if (IS_ERR(obj))
		return ERR_CAST(obj);

	cmd = i915_gem_object_pin_map(obj, I915_MAP_WB);
	if (IS_ERR(cmd)) {
		err = PTR_ERR(cmd);
		goto err;
	}

	GEM_BUG_ON(offset + (count - 1) * PAGE_SIZE > vma->node.size);
	offset += vma->node.start;

	for (n = 0; n < count; n++) {
		if (gen >= 8) {
			*cmd++ = MI_STORE_DWORD_IMM_GEN4;
			*cmd++ = lower_32_bits(offset);
			*cmd++ = upper_32_bits(offset);
			*cmd++ = value;
		} else if (gen >= 4) {
			*cmd++ = MI_STORE_DWORD_IMM_GEN4 |
				(gen < 6 ? MI_USE_GGTT : 0);
			*cmd++ = 0;
			*cmd++ = offset;
			*cmd++ = value;
		} else {
			*cmd++ = MI_STORE_DWORD_IMM | MI_MEM_VIRTUAL;
			*cmd++ = offset;
			*cmd++ = value;
		}
		offset += PAGE_SIZE;
	}
	*cmd = MI_BATCH_BUFFER_END;
	i915_gem_object_unpin_map(obj);

	err = i915_gem_object_set_to_gtt_domain(obj, false);
	if (err)
		goto err;

	vma = i915_vma_instance(obj, vma->vm, NULL);
	if (IS_ERR(vma)) {
		err = PTR_ERR(vma);
		goto err;
	}

	err = i915_vma_pin(vma, 0, 0, PIN_USER);
	if (err)
		goto err;

	return vma;

err:
	i915_gem_object_put(obj);
	return ERR_PTR(err);
}

static unsigned long real_page_count(struct drm_i915_gem_object *obj)
{
	return huge_gem_object_phys_size(obj) >> PAGE_SHIFT;
}

static unsigned long fake_page_count(struct drm_i915_gem_object *obj)
{
	return huge_gem_object_dma_size(obj) >> PAGE_SHIFT;
}

static int gpu_fill(struct drm_i915_gem_object *obj,
		    struct i915_gem_context *ctx,
		    struct intel_engine_cs *engine,
		    unsigned int dw)
{
	struct drm_i915_private *i915 = to_i915(obj->base.dev);
	struct i915_address_space *vm =
		ctx->ppgtt ? &ctx->ppgtt->vm : &i915->ggtt.vm;
	struct i915_request *rq;
	struct i915_vma *vma;
	struct i915_vma *batch;
	unsigned int flags;
	int err;

	GEM_BUG_ON(obj->base.size > vm->total);
	GEM_BUG_ON(!intel_engine_can_store_dword(engine));

	vma = i915_vma_instance(obj, vm, NULL);
	if (IS_ERR(vma))
		return PTR_ERR(vma);

	err = i915_gem_object_set_to_gtt_domain(obj, false);
	if (err)
		return err;

	err = i915_vma_pin(vma, 0, 0, PIN_HIGH | PIN_USER);
	if (err)
		return err;

	/* Within the GTT the huge objects maps every page onto
	 * its 1024 real pages (using phys_pfn = dma_pfn % 1024).
	 * We set the nth dword within the page using the nth
	 * mapping via the GTT - this should exercise the GTT mapping
	 * whilst checking that each context provides a unique view
	 * into the object.
	 */
	batch = gpu_fill_dw(vma,
			    (dw * real_page_count(obj)) << PAGE_SHIFT |
			    (dw * sizeof(u32)),
			    real_page_count(obj),
			    dw);
	if (IS_ERR(batch)) {
		err = PTR_ERR(batch);
		goto err_vma;
	}

	rq = i915_request_alloc(engine, ctx);
	if (IS_ERR(rq)) {
		err = PTR_ERR(rq);
		goto err_batch;
	}

	flags = 0;
	if (INTEL_GEN(vm->i915) <= 5)
		flags |= I915_DISPATCH_SECURE;

	err = engine->emit_bb_start(rq,
				    batch->node.start, batch->node.size,
				    flags);
	if (err)
		goto err_request;

	err = i915_vma_move_to_active(batch, rq, 0);
	if (err)
		goto skip_request;

	err = i915_vma_move_to_active(vma, rq, EXEC_OBJECT_WRITE);
	if (err)
		goto skip_request;

	i915_gem_object_set_active_reference(batch->obj);
	i915_vma_unpin(batch);
	i915_vma_close(batch);

	i915_vma_unpin(vma);

	i915_request_add(rq);

	return 0;

skip_request:
	i915_request_skip(rq, err);
err_request:
	i915_request_add(rq);
err_batch:
	i915_vma_unpin(batch);
	i915_vma_put(batch);
err_vma:
	i915_vma_unpin(vma);
	return err;
}

static int cpu_fill(struct drm_i915_gem_object *obj, u32 value)
{
	const bool has_llc = HAS_LLC(to_i915(obj->base.dev));
	unsigned int n, m, need_flush;
	int err;

	err = i915_gem_obj_prepare_shmem_write(obj, &need_flush);
	if (err)
		return err;

	for (n = 0; n < real_page_count(obj); n++) {
		u32 *map;

		map = kmap_atomic(i915_gem_object_get_page(obj, n));
		for (m = 0; m < DW_PER_PAGE; m++)
			map[m] = value;
		if (!has_llc)
			drm_clflush_virt_range(map, PAGE_SIZE);
		kunmap_atomic(map);
	}

	i915_gem_obj_finish_shmem_access(obj);
	obj->read_domains = I915_GEM_DOMAIN_GTT | I915_GEM_DOMAIN_CPU;
	obj->write_domain = 0;
	return 0;
}

static int cpu_check(struct drm_i915_gem_object *obj, unsigned int max)
{
	unsigned int n, m, needs_flush;
	int err;

	err = i915_gem_obj_prepare_shmem_read(obj, &needs_flush);
	if (err)
		return err;

	for (n = 0; n < real_page_count(obj); n++) {
		u32 *map;

		map = kmap_atomic(i915_gem_object_get_page(obj, n));
		if (needs_flush & CLFLUSH_BEFORE)
			drm_clflush_virt_range(map, PAGE_SIZE);

		for (m = 0; m < max; m++) {
			if (map[m] != m) {
				pr_err("Invalid value at page %d, offset %d: found %x expected %x\n",
				       n, m, map[m], m);
				err = -EINVAL;
				goto out_unmap;
			}
		}

		for (; m < DW_PER_PAGE; m++) {
			if (map[m] != STACK_MAGIC) {
				pr_err("Invalid value at page %d, offset %d: found %x expected %x\n",
				       n, m, map[m], STACK_MAGIC);
				err = -EINVAL;
				goto out_unmap;
			}
		}

out_unmap:
		kunmap_atomic(map);
		if (err)
			break;
	}

	i915_gem_obj_finish_shmem_access(obj);
	return err;
}

static int file_add_object(struct drm_file *file,
			    struct drm_i915_gem_object *obj)
{
	int err;

	GEM_BUG_ON(obj->base.handle_count);

	/* tie the object to the drm_file for easy reaping */
	err = idr_alloc(&file->object_idr, &obj->base, 1, 0, GFP_KERNEL);
	if (err < 0)
		return  err;

	i915_gem_object_get(obj);
	obj->base.handle_count++;
	return 0;
}

static struct drm_i915_gem_object *
create_test_object(struct i915_gem_context *ctx,
		   struct drm_file *file,
		   struct list_head *objects)
{
	struct drm_i915_gem_object *obj;
	struct i915_address_space *vm =
		ctx->ppgtt ? &ctx->ppgtt->vm : &ctx->i915->ggtt.vm;
	u64 size;
	int err;

	size = min(vm->total / 2, 1024ull * DW_PER_PAGE * PAGE_SIZE);
	size = round_down(size, DW_PER_PAGE * PAGE_SIZE);

	obj = huge_gem_object(ctx->i915, DW_PER_PAGE * PAGE_SIZE, size);
	if (IS_ERR(obj))
		return obj;

	err = file_add_object(file, obj);
	i915_gem_object_put(obj);
	if (err)
		return ERR_PTR(err);

	err = cpu_fill(obj, STACK_MAGIC);
	if (err) {
		pr_err("Failed to fill object with cpu, err=%d\n",
		       err);
		return ERR_PTR(err);
	}

	list_add_tail(&obj->st_link, objects);
	return obj;
}

static unsigned long max_dwords(struct drm_i915_gem_object *obj)
{
	unsigned long npages = fake_page_count(obj);

	GEM_BUG_ON(!IS_ALIGNED(npages, DW_PER_PAGE));
	return npages / DW_PER_PAGE;
}

static int igt_ctx_exec(void *arg)
{
	struct drm_i915_private *i915 = arg;
	struct drm_i915_gem_object *obj = NULL;
	unsigned long ncontexts, ndwords, dw;
	struct drm_file *file;
	IGT_TIMEOUT(end_time);
	LIST_HEAD(objects);
	struct live_test t;
	int err = -ENODEV;

	/*
	 * Create a few different contexts (with different mm) and write
	 * through each ctx/mm using the GPU making sure those writes end
	 * up in the expected pages of our obj.
	 */

	if (!DRIVER_CAPS(i915)->has_logical_contexts)
		return 0;

	file = mock_file(i915);
	if (IS_ERR(file))
		return PTR_ERR(file);

	mutex_lock(&i915->drm.struct_mutex);

	err = begin_live_test(&t, i915, __func__, "");
	if (err)
		goto out_unlock;

	ncontexts = 0;
	ndwords = 0;
	dw = 0;
	while (!time_after(jiffies, end_time)) {
		struct intel_engine_cs *engine;
		struct i915_gem_context *ctx;
		unsigned int id;

		ctx = i915_gem_create_context(i915, file->driver_priv);
		if (IS_ERR(ctx)) {
			err = PTR_ERR(ctx);
			goto out_unlock;
		}

		for_each_engine(engine, i915, id) {
			if (!engine->context_size)
				continue; /* No logical context support in HW */

			if (!intel_engine_can_store_dword(engine))
				continue;

			if (!obj) {
				obj = create_test_object(ctx, file, &objects);
				if (IS_ERR(obj)) {
					err = PTR_ERR(obj);
					goto out_unlock;
				}
			}

			intel_runtime_pm_get(i915);
			err = gpu_fill(obj, ctx, engine, dw);
			intel_runtime_pm_put(i915);
			if (err) {
				pr_err("Failed to fill dword %lu [%lu/%lu] with gpu (%s) in ctx %u [full-ppgtt? %s], err=%d\n",
				       ndwords, dw, max_dwords(obj),
				       engine->name, ctx->hw_id,
				       yesno(!!ctx->ppgtt), err);
				goto out_unlock;
			}

			if (++dw == max_dwords(obj)) {
				obj = NULL;
				dw = 0;
			}
			ndwords++;
		}
		ncontexts++;
	}
	pr_info("Submitted %lu contexts (across %u engines), filling %lu dwords\n",
		ncontexts, INTEL_INFO(i915)->num_rings, ndwords);

	dw = 0;
	list_for_each_entry(obj, &objects, st_link) {
		unsigned int rem =
			min_t(unsigned int, ndwords - dw, max_dwords(obj));

		err = cpu_check(obj, rem);
		if (err)
			break;

		dw += rem;
	}

out_unlock:
	if (end_live_test(&t))
		err = -EIO;
	mutex_unlock(&i915->drm.struct_mutex);

	mock_file_free(i915, file);
	return err;
}

static int igt_ctx_readonly(void *arg)
{
	struct drm_i915_private *i915 = arg;
	struct drm_i915_gem_object *obj = NULL;
	struct i915_gem_context *ctx;
	struct i915_hw_ppgtt *ppgtt;
	unsigned long ndwords, dw;
	struct drm_file *file;
	I915_RND_STATE(prng);
	IGT_TIMEOUT(end_time);
	LIST_HEAD(objects);
	struct live_test t;
	int err = -ENODEV;

	/*
	 * Create a few read-only objects (with the occasional writable object)
	 * and try to write into these object checking that the GPU discards
	 * any write to a read-only object.
	 */

	file = mock_file(i915);
	if (IS_ERR(file))
		return PTR_ERR(file);

	mutex_lock(&i915->drm.struct_mutex);

	err = begin_live_test(&t, i915, __func__, "");
	if (err)
		goto out_unlock;

	ctx = i915_gem_create_context(i915, file->driver_priv);
	if (IS_ERR(ctx)) {
		err = PTR_ERR(ctx);
		goto out_unlock;
	}

	ppgtt = ctx->ppgtt ?: i915->mm.aliasing_ppgtt;
	if (!ppgtt || !ppgtt->vm.has_read_only) {
		err = 0;
		goto out_unlock;
	}

	ndwords = 0;
	dw = 0;
	while (!time_after(jiffies, end_time)) {
		struct intel_engine_cs *engine;
		unsigned int id;

		for_each_engine(engine, i915, id) {
			if (!intel_engine_can_store_dword(engine))
				continue;

			if (!obj) {
				obj = create_test_object(ctx, file, &objects);
				if (IS_ERR(obj)) {
					err = PTR_ERR(obj);
					goto out_unlock;
				}

				if (prandom_u32_state(&prng) & 1)
					i915_gem_object_set_readonly(obj);
			}

			intel_runtime_pm_get(i915);
			err = gpu_fill(obj, ctx, engine, dw);
			intel_runtime_pm_put(i915);
			if (err) {
				pr_err("Failed to fill dword %lu [%lu/%lu] with gpu (%s) in ctx %u [full-ppgtt? %s], err=%d\n",
				       ndwords, dw, max_dwords(obj),
				       engine->name, ctx->hw_id,
				       yesno(!!ctx->ppgtt), err);
				goto out_unlock;
			}

			if (++dw == max_dwords(obj)) {
				obj = NULL;
				dw = 0;
			}
			ndwords++;
		}
	}
	pr_info("Submitted %lu dwords (across %u engines)\n",
		ndwords, INTEL_INFO(i915)->num_rings);

	dw = 0;
	list_for_each_entry(obj, &objects, st_link) {
		unsigned int rem =
			min_t(unsigned int, ndwords - dw, max_dwords(obj));
		unsigned int num_writes;

		num_writes = rem;
		if (i915_gem_object_is_readonly(obj))
			num_writes = 0;

		err = cpu_check(obj, num_writes);
		if (err)
			break;

		dw += rem;
	}

out_unlock:
	if (end_live_test(&t))
		err = -EIO;
	mutex_unlock(&i915->drm.struct_mutex);

	mock_file_free(i915, file);
	return err;
}

static int check_scratch(struct i915_gem_context *ctx, u64 offset)
{
	struct drm_mm_node *node =
		__drm_mm_interval_first(&ctx->ppgtt->vm.mm,
					offset, offset + sizeof(u32) - 1);
	if (!node || node->start > offset)
		return 0;

	GEM_BUG_ON(offset >= node->start + node->size);

	pr_err("Target offset 0x%08x_%08x overlaps with a node in the mm!\n",
	       upper_32_bits(offset), lower_32_bits(offset));
	return -EINVAL;
}

static int write_to_scratch(struct i915_gem_context *ctx,
			    struct intel_engine_cs *engine,
			    u64 offset, u32 value)
{
	struct drm_i915_private *i915 = ctx->i915;
	struct drm_i915_gem_object *obj;
	struct i915_request *rq;
	struct i915_vma *vma;
	u32 *cmd;
	int err;

	GEM_BUG_ON(offset < I915_GTT_PAGE_SIZE);

	obj = i915_gem_object_create_internal(i915, PAGE_SIZE);
	if (IS_ERR(obj))
		return PTR_ERR(obj);

	cmd = i915_gem_object_pin_map(obj, I915_MAP_WB);
	if (IS_ERR(cmd)) {
		err = PTR_ERR(cmd);
		goto err;
	}

	*cmd++ = MI_STORE_DWORD_IMM_GEN4;
	if (INTEL_GEN(i915) >= 8) {
		*cmd++ = lower_32_bits(offset);
		*cmd++ = upper_32_bits(offset);
	} else {
		*cmd++ = 0;
		*cmd++ = offset;
	}
	*cmd++ = value;
	*cmd = MI_BATCH_BUFFER_END;
	i915_gem_object_unpin_map(obj);

	err = i915_gem_object_set_to_gtt_domain(obj, false);
	if (err)
		goto err;

	vma = i915_vma_instance(obj, &ctx->ppgtt->vm, NULL);
	if (IS_ERR(vma)) {
		err = PTR_ERR(vma);
		goto err;
	}

	err = i915_vma_pin(vma, 0, 0, PIN_USER | PIN_OFFSET_FIXED);
	if (err)
		goto err;

	err = check_scratch(ctx, offset);
	if (err)
		goto err_unpin;

	rq = i915_request_alloc(engine, ctx);
	if (IS_ERR(rq)) {
		err = PTR_ERR(rq);
		goto err_unpin;
	}

	err = engine->emit_bb_start(rq, vma->node.start, vma->node.size, 0);
	if (err)
		goto err_request;

	err = i915_vma_move_to_active(vma, rq, 0);
	if (err)
		goto skip_request;

	i915_gem_object_set_active_reference(obj);
	i915_vma_unpin(vma);
	i915_vma_close(vma);

	i915_request_add(rq);

	return 0;

skip_request:
	i915_request_skip(rq, err);
err_request:
	i915_request_add(rq);
err_unpin:
	i915_vma_unpin(vma);
err:
	i915_gem_object_put(obj);
	return err;
}

static int read_from_scratch(struct i915_gem_context *ctx,
			     struct intel_engine_cs *engine,
			     u64 offset, u32 *value)
{
	struct drm_i915_private *i915 = ctx->i915;
	struct drm_i915_gem_object *obj;
	const u32 RCS_GPR0 = 0x2600; /* not all engines have their own GPR! */
	const u32 result = 0x100;
	struct i915_request *rq;
	struct i915_vma *vma;
	u32 *cmd;
	int err;

	GEM_BUG_ON(offset < I915_GTT_PAGE_SIZE);

	obj = i915_gem_object_create_internal(i915, PAGE_SIZE);
	if (IS_ERR(obj))
		return PTR_ERR(obj);

	cmd = i915_gem_object_pin_map(obj, I915_MAP_WB);
	if (IS_ERR(cmd)) {
		err = PTR_ERR(cmd);
		goto err;
	}

	memset(cmd, POISON_INUSE, PAGE_SIZE);
	if (INTEL_GEN(i915) >= 8) {
		*cmd++ = MI_LOAD_REGISTER_MEM_GEN8;
		*cmd++ = RCS_GPR0;
		*cmd++ = lower_32_bits(offset);
		*cmd++ = upper_32_bits(offset);
		*cmd++ = MI_STORE_REGISTER_MEM_GEN8;
		*cmd++ = RCS_GPR0;
		*cmd++ = result;
		*cmd++ = 0;
	} else {
		*cmd++ = MI_LOAD_REGISTER_MEM;
		*cmd++ = RCS_GPR0;
		*cmd++ = offset;
		*cmd++ = MI_STORE_REGISTER_MEM;
		*cmd++ = RCS_GPR0;
		*cmd++ = result;
	}
	*cmd = MI_BATCH_BUFFER_END;
	i915_gem_object_unpin_map(obj);

	err = i915_gem_object_set_to_gtt_domain(obj, false);
	if (err)
		goto err;

	vma = i915_vma_instance(obj, &ctx->ppgtt->vm, NULL);
	if (IS_ERR(vma)) {
		err = PTR_ERR(vma);
		goto err;
	}

	err = i915_vma_pin(vma, 0, 0, PIN_USER | PIN_OFFSET_FIXED);
	if (err)
		goto err;

	err = check_scratch(ctx, offset);
	if (err)
		goto err_unpin;

	rq = i915_request_alloc(engine, ctx);
	if (IS_ERR(rq)) {
		err = PTR_ERR(rq);
		goto err_unpin;
	}

	err = engine->emit_bb_start(rq, vma->node.start, vma->node.size, 0);
	if (err)
		goto err_request;

	err = i915_vma_move_to_active(vma, rq, EXEC_OBJECT_WRITE);
	if (err)
		goto skip_request;

	i915_vma_unpin(vma);
	i915_vma_close(vma);

	i915_request_add(rq);

	err = i915_gem_object_set_to_cpu_domain(obj, false);
	if (err)
		goto err;

	cmd = i915_gem_object_pin_map(obj, I915_MAP_WB);
	if (IS_ERR(cmd)) {
		err = PTR_ERR(cmd);
		goto err;
	}

	*value = cmd[result / sizeof(*cmd)];
	i915_gem_object_unpin_map(obj);
	i915_gem_object_put(obj);

	return 0;

skip_request:
	i915_request_skip(rq, err);
err_request:
	i915_request_add(rq);
err_unpin:
	i915_vma_unpin(vma);
err:
	i915_gem_object_put(obj);
	return err;
}

static int igt_vm_isolation(void *arg)
{
	struct drm_i915_private *i915 = arg;
	struct i915_gem_context *ctx_a, *ctx_b;
	struct intel_engine_cs *engine;
	struct drm_file *file;
	I915_RND_STATE(prng);
	unsigned long count;
	struct live_test t;
	unsigned int id;
	u64 vm_total;
	int err;

	if (INTEL_GEN(i915) < 7)
		return 0;

	/*
	 * The simple goal here is that a write into one context is not
	 * observed in a second (separate page tables and scratch).
	 */

	file = mock_file(i915);
	if (IS_ERR(file))
		return PTR_ERR(file);

	mutex_lock(&i915->drm.struct_mutex);

	err = begin_live_test(&t, i915, __func__, "");
	if (err)
		goto out_unlock;

	ctx_a = i915_gem_create_context(i915, file->driver_priv);
	if (IS_ERR(ctx_a)) {
		err = PTR_ERR(ctx_a);
		goto out_unlock;
	}

	ctx_b = i915_gem_create_context(i915, file->driver_priv);
	if (IS_ERR(ctx_b)) {
		err = PTR_ERR(ctx_b);
		goto out_unlock;
	}

	/* We can only test vm isolation, if the vm are distinct */
	if (ctx_a->ppgtt == ctx_b->ppgtt)
		goto out_unlock;

	vm_total = ctx_a->ppgtt->vm.total;
	GEM_BUG_ON(ctx_b->ppgtt->vm.total != vm_total);
	vm_total -= I915_GTT_PAGE_SIZE;

	intel_runtime_pm_get(i915);

	count = 0;
	for_each_engine(engine, i915, id) {
		IGT_TIMEOUT(end_time);
		unsigned long this = 0;

		if (!intel_engine_can_store_dword(engine))
			continue;

		while (!__igt_timeout(end_time, NULL)) {
			u32 value = 0xc5c5c5c5;
			u64 offset;

			div64_u64_rem(i915_prandom_u64_state(&prng),
				      vm_total, &offset);
			offset &= ~sizeof(u32);
			offset += I915_GTT_PAGE_SIZE;

			err = write_to_scratch(ctx_a, engine,
					       offset, 0xdeadbeef);
			if (err == 0)
				err = read_from_scratch(ctx_b, engine,
							offset, &value);
			if (err)
				goto out_rpm;

			if (value) {
				pr_err("%s: Read %08x from scratch (offset 0x%08x_%08x), after %lu reads!\n",
				       engine->name, value,
				       upper_32_bits(offset),
				       lower_32_bits(offset),
				       this);
				err = -EINVAL;
				goto out_rpm;
			}

			this++;
		}
		count += this;
	}
	pr_info("Checked %lu scratch offsets across %d engines\n",
		count, INTEL_INFO(i915)->num_rings);

out_rpm:
	intel_runtime_pm_put(i915);
out_unlock:
	if (end_live_test(&t))
		err = -EIO;
	mutex_unlock(&i915->drm.struct_mutex);

	mock_file_free(i915, file);
	return err;
}

static __maybe_unused const char *
__engine_name(struct drm_i915_private *i915, unsigned int engines)
{
	struct intel_engine_cs *engine;
	unsigned int tmp;

	if (engines == ALL_ENGINES)
		return "all";

	for_each_engine_masked(engine, i915, engines, tmp)
		return engine->name;

	return "none";
}

static int __igt_switch_to_kernel_context(struct drm_i915_private *i915,
					  struct i915_gem_context *ctx,
					  unsigned int engines)
{
	struct intel_engine_cs *engine;
	unsigned int tmp;
	int err;

	GEM_TRACE("Testing %s\n", __engine_name(i915, engines));
	for_each_engine_masked(engine, i915, engines, tmp) {
		struct i915_request *rq;

		rq = i915_request_alloc(engine, ctx);
		if (IS_ERR(rq))
			return PTR_ERR(rq);

		i915_request_add(rq);
	}

	err = i915_gem_switch_to_kernel_context(i915);
	if (err)
		return err;

	for_each_engine_masked(engine, i915, engines, tmp) {
		if (!engine_has_kernel_context_barrier(engine)) {
			pr_err("kernel context not last on engine %s!\n",
			       engine->name);
			return -EINVAL;
		}
	}

	err = i915_gem_wait_for_idle(i915,
				     I915_WAIT_LOCKED,
				     MAX_SCHEDULE_TIMEOUT);
	if (err)
		return err;

	GEM_BUG_ON(i915->gt.active_requests);
	for_each_engine_masked(engine, i915, engines, tmp) {
		if (engine->last_retired_context->gem_context != i915->kernel_context) {
			pr_err("engine %s not idling in kernel context!\n",
			       engine->name);
			return -EINVAL;
		}
	}

	err = i915_gem_switch_to_kernel_context(i915);
	if (err)
		return err;

	if (i915->gt.active_requests) {
		pr_err("switch-to-kernel-context emitted %d requests even though it should already be idling in the kernel context\n",
		       i915->gt.active_requests);
		return -EINVAL;
	}

	for_each_engine_masked(engine, i915, engines, tmp) {
		if (!intel_engine_has_kernel_context(engine)) {
			pr_err("kernel context not last on engine %s!\n",
			       engine->name);
			return -EINVAL;
		}
	}

	return 0;
}

static int igt_switch_to_kernel_context(void *arg)
{
	struct drm_i915_private *i915 = arg;
	struct intel_engine_cs *engine;
	struct i915_gem_context *ctx;
	enum intel_engine_id id;
	int err;

	/*
	 * A core premise of switching to the kernel context is that
	 * if an engine is already idling in the kernel context, we
	 * do not emit another request and wake it up. The other being
	 * that we do indeed end up idling in the kernel context.
	 */

	mutex_lock(&i915->drm.struct_mutex);
	intel_runtime_pm_get(i915);

	ctx = kernel_context(i915);
	if (IS_ERR(ctx)) {
		mutex_unlock(&i915->drm.struct_mutex);
		return PTR_ERR(ctx);
	}

	/* First check idling each individual engine */
	for_each_engine(engine, i915, id) {
		err = __igt_switch_to_kernel_context(i915, ctx, BIT(id));
		if (err)
			goto out_unlock;
	}

	/* Now en masse */
	err = __igt_switch_to_kernel_context(i915, ctx, ALL_ENGINES);
	if (err)
		goto out_unlock;

out_unlock:
	GEM_TRACE_DUMP_ON(err);
	if (igt_flush_test(i915, I915_WAIT_LOCKED))
		err = -EIO;

	intel_runtime_pm_put(i915);
	mutex_unlock(&i915->drm.struct_mutex);

	kernel_context_close(ctx);
	return err;
}

int i915_gem_context_mock_selftests(void)
{
	static const struct i915_subtest tests[] = {
		SUBTEST(igt_switch_to_kernel_context),
	};
	struct drm_i915_private *i915;
	int err;

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

	err = i915_subtests(tests, i915);

	drm_dev_put(&i915->drm);
	return err;
}

int i915_gem_context_live_selftests(struct drm_i915_private *dev_priv)
{
	static const struct i915_subtest tests[] = {
		SUBTEST(igt_switch_to_kernel_context),
		SUBTEST(live_nop_switch),
		SUBTEST(igt_ctx_exec),
		SUBTEST(igt_ctx_readonly),
		SUBTEST(igt_vm_isolation),
	};

	if (i915_terminally_wedged(&dev_priv->gpu_error))
		return 0;

	return i915_subtests(tests, dev_priv);
}